Correlation between abnormal hippocampal neural activities and spatial cognitive impairments in the model mice of schizophrenia and therapeutic effects of aripiprazole

Correlation between abnormal hippocampal neural activities and spatial cognitive impairments in the model mice of schizophrenia and therapeutic effects of aripiprazole | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Correlation between abnormal hippocampal neural activities and spatial cognitive impairments in the model mice of schizophrenia and therapeutic effects of aripiprazole Ling Qin, Zijie Li, Xueying Yang, Xueru Wang, Xuejiao Wang, Huangyu Wang, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6252679/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Spatial cognitive-behavioral deficits represent core clinical symptoms of schizophrenia (SZ), yet their neurophysiological mechanisms and effective treatment strategies remain unclear. Previous research has indicated a reduction in hippocampal volume and weakened intercellular connectivity in SZ patients, but the causal link between these hippocampal abnormalities and spatial cognitive impairments is poorly defined. To investigate this relationship, we used a virtual spatial location (VSL) task and in vivo calcium imaging in MK-801-treated mice. Furthermore we evaluated the therapeutic effects of aripiprazole (ARI). Behavioral analyses revealed that MK-801-treated mice exhibited hyperactivity (increased locomotor distance and speed) and pronounced spatial working memory deficits. Calcium imaging in the hippocampal dorsal CA1 (dCA1) region demonstrated aberrant neuronal hyperactivity, characterized by elevated calcium signal frequency, amplitude, and half-width duration, alongside impaired neural synchronization and diminished encoding precision for spatial-reward associations. ARI treatment significantly mitigated these behavioral and neuronal abnormalities. These findings establish a direct correlation between MK-801-induced hippocampal excitatory dysregulation and spatial cognitive deficits, while highlighting ARI’s therapeutic potential in mitigating schizophrenia-related spatial cognitive-behavioral impairments. Biological sciences/Neuroscience/Learning and memory/Hippocampus Biological sciences/Neuroscience Schizophrenia Spatial cognition Hippocampal abnormalities NMDAR hypofunction Calcium imaging Aripiprazole Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Spatial cognition, a core component of cognitive function, enables animals to perceive spatial information in environment and integrate it into a complete cognitive map [ 1 ] . Schizophrenia (SZ) is a prevalent mental disorder characterized primarily by positive symptoms, negative symptoms, and cognitive impairments [ 2 , 3 ] . Spatial cognition impairment, a common aspect of cognitive dysfunction found in SZ patients, manifests in patients often struggle with self-localization and environmental navigation, [ 1 , 2 ] . Previous studies have reported the hippocampal dorsal CA1 (dCA1) serving as a key brain area for spatial cognition function [ 4 ] . The majority of excitatory hippocampal neurons have stable and location-based receptive fields (place fields). These cells called place cell can encode and retrieval spatial information [ 5 ] . Clinical studies have shown that hippocampal damage typically results significant impairments in spatial cognition and memory [ 6 ] . In patients with SZ, dCA1 atrophy and decreased density of dendritic spines have been observed [ 7 ] . Hippocampal structural lesions appear in the early stages of schizophrenia, suggesting that these symptoms are not secondary to schizophrenia or treatment measures. Neuropharmacological research has also found the level of excitatory neurotransmitter glutamate is abnormally elevated [ 8 ] . Additionally, further research has found that patients with SZ have weakened functional connections with upstream brain areas such as the anterior cingulate cortex and the entorhinal cortex [ 9 ] . This is compounded by reduced neuroplasticity in the dCA1, which likely underlies persistent cognitive impairments [ 10 ] . While current evidence has demonstrated the presence of spatial cognition impairments in SZ patients and the associated structural and functional abnormalities in the hippocampal dCA1 area, the causal relationship between these abnormalities remains unclear. To address this issue, selecting appropriate SZ animal models for in vivo neurophysiological studies is particularly crucial. Pharmacological and genetic evidence implicates NMDA receptor (NMDAR) hypofunction as key characteristic of SZ pathophysiology [ 11 , 12 ] . The application of NMDAR antagonists like dizocilpine (MK-801) can induce cognitive and behavioral impairments similar to those observed in SZ patients [ 13 ] . Many studies have shown that MK-801 damages spatial memory in the Morris water maze and radial-arm maze [ 14 , 15 ] . However, the absence of direct hippocampal neuronal recordings in SZ model mice has prevented definitive conclusions about whether dCA1 neuronal dysfunction drives observed behavioral impairments. To address this gap, it is necessary to perform in vivo recordings of the dynamic activity of individual hippocampal neurons while SZ model mice undertake spatial cognitive tasks. Recent researches in recording hippocampal neuronal activity have used large view calcium imaging as a novel methodology [ 16 ] . This technique allows monitoring hundreds of neurons simultaneously and recording specific cell subtypes labeled with calcium indicators driven by promoters such as Thy1 or Camk2 [ 17 ] . Compared with electrophysiological recording, large view calcium imaging might be less affected by movements [ 18 ] . Large view calcium imaging enables the simultaneous recording of both the precise firing times and spatial locations, thereby providing a better understanding of the relationship between hippocampal neural activity and spatial cognitive function. Because large view calcium imaging requires the use of a large objective lens, the mice need to be head-fixed under the objective lens. In order to detect their hippocampus-related spatial cognitive ability [ 20 , 21 ] , previous studies have used virtual reality (VR) technology to ensure real-time synchronization between the virtual environment and the mouse's running on a treadmill [ 19 ] . In this study, we combined the virtual spatial location (VSL) task and calcium imaging recording in hippocampus, in order to explore the correlation between abnormal activity of dCA1 place cell and spatial cognition impairments in the SZ mouse model. Schizophrenia is often associated with abnormal levels of dopamine [ 22 ] . Beyond mechanistic insights, this study explores dopamine modulation as a potential therapeutic strategy. Aripiprazole (ARI) can partially activate dopamine D2 receptors, and stabilize dopamine function [ 23 ] . ARI has been proven to alleviate the positive and negative symptoms of SZ [ 24 ] , its effects on correcting abnormal hippocampal neuronal activity and potential impacts on spatial cognition impairments remain unclear. Though ARI alleviates positive and negative symptoms [23, 24], its effects on correcting dCA1 neuronal dysfunction and spatial cognition deficits is unknown. Therefore, we evaluated the potential therapeutic effects of ARI. The results of this study will provide critical evidence for refining treatment strategies targeting cognitive impairments in SZ. Materials and methods Animals In this study, we selected C57BL/6 mice aged 6–8 weeks, weighing between 30–40 g, from Vital River Laboratories in China. Additionally, we used FosCreER mice [B6.129(Cg)-Fostm1.1(cre/ERT2)Luo/J, #021882, Jackson Laboratories, USA] and Ai14 mice [B6.Cg-Gt(ROSA)26Sortm14(CAG-tdTomato)Hze/J, #007914, Jackson Laboratories, USA]. FosTRAP mice were obtained by breeding female Ai14 mice with male FosCreER mice. All experimental animals were maintained and bred to meet the following conditions: an environmental temperature of 22–24°C, humidity levels between 50–55%, ensuring a 12-hour light/dark cycle. Animal care strictly followed the policies and procedures outlined in the "Guide for the Care and Use of Laboratory Animals" published by the National Institutes of Health (NIH), USA. All related procedures were approved by the Animal Ethics Committee of China Medical University (CEUA). All surgical operations were performed under complete anesthesia to minimize pain and reduce the number of animals used as much as possible. Viral Injection Anesthesia was induced using isoflurane at a concentration of 4–5%, and once the mice no longer responded to nociceptive stimuli, anesthesia was maintained with 2% isoflurane. Throughout the surgical procedure, body temperature was monitored and maintained at approximately 37°C using a thermostatic electric heating blanket. After securing the mouse‘s head in a stereotaxic apparatus, the head skin was disinfected with 75% alcohol. Under a stereomicroscope, the skin was incised to fully expose the skull and fontanelle. Based on the Paxinos & Watson brain atlas, the hippocampal dCA1 area (AP: -2.0 mm, ML: 2.0 mm) was marked with a pencil. At the specified coordinates, a 0.5 mm diameter drill bit rotating at 4,000 rpm was used to open the skull. Physiological saline was used to irrigate the hole for hemostasis, and the dura mater was pierced under micro forceps. A calcium indicator (rAAV-CaMKII-Gcamp6s) was diluted in physiological saline at a 1:5 ratio and loaded into a microinjector (10 µl) placed in a micropump. Under microscopic guidance, the glass pipette was adjusted to the designated depth(DV: -1.5 mm), and the calcium indicator was slowly injected into the dCA1 region at a rate of 20 nl/min, injecting a total of 200 nl. After the injection, the needle was left in place for 10 minutes to allow for sufficient viral diffusion before it was slowly withdrawn. Seal the injection site with dental cement and then suture the skin. Lens Insertion Two weeks following the viral injection, the mice underwent a craniotomy procedure, with anesthesia induction and maintenance consistent with previously described methods. The mouse's head was secured in a stereotaxic device. Using a 0.5 mm drill bit, a circular craniotomy of 4 mm diameter was centered over the coordinates of the dCA1 area. After exposing the cortex above the hippocampus, the brain tissue over the hippocampus (~ 1mm) was aspirated using a suction device. The site was irrigated with physiological saline to achieve hemostasis, and a metal cannula (sealed at one end with a PVC piece) was implanted into the bone window, then fixed with dental cement. Two screws were inserted posterior to the cranium, Two metal rings with a diameter of 0.2 mm were implanted on both sides of the dental cement for head fixation After the surgery, the mice were allowed to recover consciousness before being transferred to individual cages. The mice were allowed to recover for one week before proceeding with further experimental manipulations. Virtual spatial location Task Two weeks after the surgery, mice equipped with head plates were head-fixed on a turntable. Before the initial training of the virtual spatial location (VSL) task, mice were allowed to run on the turntable for 5–10 minutes as a habituation phase. This familiarization phase was conducted daily for at least five consecutive days. Prior to the commencement of formal behavioral training, water restriction was enforced for a minimum of 36 hours to ensure that the reward during training effectively motivated the mice to maintain sustained engagement. Additionally, mice were monitored daily for weight and appearance to ensure no behavioral abnormalities during training. A virtual unidirectional linear track (Fig. 1 B) was created using unity3D. At the start of training, mice were positioned at the origin of the virtual track and then ran from the starting point to the endpoint. The target area was marked on the floor with a mosaic pattern as a cue. The task was divided into non-delayed and delayed phases, requiring different conditions to trigger rewards. During the non-delayed phase, mice received water rewards immediately upon crossing the target areas. During the delay phase, the mice were required to pause in the target area for at least 1.5 seconds to receive a reward. The motion trajectories of the mice on the virtual track were analyzed using a custom Python program based on their positions. Targeted Recombination in Fos-Active Groups After FosTRAP mice (Fos-CreERT2-Ai14) administered 4-hydroxytamoxifen (4-OHT) drug, task-activated neurons express c-Fos protein and generate Cre recombinase, leading to the expression of red fluorescence (tdTomato). Prior to the commencement of the experiment, preparation of 4-OHT was conducted. 4-OHT was dissolved in ethanol at 37°C with shaking for 15 minutes to achieve a concentration of 20 mg/mL. The 4-OHT solution could be aliquoted and stored at -20°C for up to one month. On the day of use, the 4-OHT was re-dissolved in ethanol by shaking again for 15 minutes at 37°C. Corn oil was then added to adjust the final concentration of the 4-OHT solution to 5 mg/mL, followed by the vacuum centrifugation to evaporate the ethanol. FosTRAP mice underwent daily intraperitoneal injections of saline for seven consecutive days to minimize the stress response induced by experimental handling. On the eighth day, mice initially received an intraperitoneal injection 4-OHT at a dose of 50 mg/kg. Half an hour later, they were subjected to the VSL task. Three days following this, the mice were administered either saline or MK-801 (0.1 mg/kg). Subsequently, the mice were returned to their cages. 24 hours after these treatments, the mice were euthanized via cardiac perfusion for further collection and sectioning of brain tissue. Histological Sectioning and Immunofluorescence Staining The brains were extracted and fixed in 4% paraformaldehyde for 48 hours, before being transferred to a gradient sucrose solution for dehydration. For cryosectioning, the excess fluid on the brain tissue surface was first removed using filter paper. The brain tissues were then embedded in OCT compound and secured within a cryostat (CM 1900, Leica Biosystems, Germany) at -20°C. Sections of 20 µm thickness were cut from the frozen brain tissues and collected on adhesive slides. The cryosections were left at room temperature for 1 hour and then washed with PBS three times, for 5 minutes each. Drops of 10% normal goat serum were applied to the brain slices and incubated at room temperature for 1 hour to block non-specific binding. After absorbing the serum with filter paper, diluted c-Fos antibody (1:5000) was added, and the sections were incubated at 4°C for 12 hours. The brain slices were washed again with PBS three times, for 5 minutes each. A secondary antibody, goat anti-rabbit CoraLite488 (1:300), was applied and the sections were incubated in the dark at room temperature for 2 hours. After additional washing with PBS three times for 5 minutes each, an anti-fade mounting medium was added under dark conditions, followed by covering with a coverslip. Tissue sections were examined under a fluorescence microscope (BX53, Olympus, Japan). Calcium Fluorescence Imaging Recording The mouse's head was fixed in place on a turntable to facilitate in vivo calcium fluorescence imaging during running. An induction device was placed parallel over the turntable to detect rotations, capturing motion data, which was then analyzed using a computer to assess the mouse's locomotion. Prior to imaging, mice were allowed to acclimate to the experimental environment for 1 hour, after which imaging commenced. The excitation light of the microscope was set to 485 nm to stimulate the GCaMP6s fluorescent protein, and a custom-built software was used to simultaneously trigger both the turntable and the imaging recording devices. Fluorescence microscopy was employed to capture the dynamic changes in neuronal calcium signaling. To prevent excessive quenching of the fluorescence signal, recording began concurrently with the initiation of the VSL task, with each recording session lasting 15 minutes. Calcium Imaging Data Analysis Initially, the ImageJ plugin was utilized to stabilize the imagery, mitigating the effects of motion-induced jitter during recording and facilitating the identification of individual neurons. The Python suite2p toolbox was used to identify and analyze neurons. Calcium signals were expressed as ΔF/F, where the baseline fluorescence (F 0 ) was calculated as the mean fluorescence intensity across the entire recording session. The ΔF/F value at each time point was derived from (F(t) − F 0 )/ F 0 , with F(t) being the raw fluorescence signal. We used the ‘find_peak’ function from the Python scipy package to calculate the frequency and amplitude of neuronal calcium signal activity. Neurons with signal decay exceeding two seconds were excluded using the OASIS toolbox ( https://github.com/j-friedrich/OASIS ), as these were considered identification failures, and the half-width of neuronal calcium signal activity was calculated. The correlation coefficient between neuronal calcium signal activities was computed using the ‘corrcoef’ function from the Python numpy package. Statistical Analysis Data conforming to a Gaussian distribution was subjected to t-test analysis, or one-way Analysis of Variance (ANOVA) followed by Tukey’s multiple comparison tests, the rank sum test was used if data did not conform to Gaussian distribution. Data are presented as mean ± Standard Error of the Mean (SEM). Results Training and Behavioral Performance of Mice in VSL Tasks Head-fixed mice navigated a virtual straight track in a virtual spatial location (VSL) task, with water rewards (~ 10 µl) delivered upon passing through a predefined target area (mosaic-marked region, Fig. 1 A-B). The VSL task was comprised of non-delayed and delay phases. During the non-delayed phase, mice received reward immediately upon entering the target area, facilitating learning and familiarization with the reward locations in the virtual environment (Fig. 1 B). Initially, the mice ran shorter distances at lower speeds. After 8–10 days training, both the running distance and speed significantly increased, indicating adaptation to running in the VR environment. Following the non-delayed training, the delay phase began, requiring the mice to pause in the target area for at least 1.5 seconds to receive a reward; if not, no reward was given. Early in the training phase, the mice frequently stopped at incorrect locations or paused too briefly, thereby reducing their chances of obtaining rewards. After 4–6 days in the delayed training phase, a reduction in running speed at the target areas suggested the mice began to recognize the association between the location and reward (Fig. 1 C) and gradually improving their success rates to stabilize at over 80%. This phenomenon indicated that the mice had formed an association between the location and reward (Fig. 1 F). Throughout the training, the mice's running distance and speed increased during the non-delayed phase and remained stable upon entering the delayed phase (Fig. 1 D and E). Distance and speed in the late stage of two phases were similar, indicating that the motivation of running behavior in different phase was same. The success rate for obtaining rewards dropped sharply from 100% in the non-delayed phase to about 50% at the start of the delayed phase, then gradually increased and stabilized above 80% as training progressed (Fig. 1 F). MK-801impaired mice’s spatial cognitive ability in the VSL Task After the training of VSL task, mice were intraperitoneal injected with the NMDA receptor antagonist MK-801 at a dose of 0.1 mg/kg before task to serve as experimental group, and saline for the control group. Thirty minutes later, the mice were engaged in the VSL task to assess the impact of MK-801 injection on their spatial cognitive behavior (Fig. 2 A). Mice received saline injections (control group) were still able to accurately pause within the target location and obtain rewards. However, following the injection of MK-801, the mice exhibited increased movement speeds (Fig. 2 D) and completed a greater number of trials, without notable deceleration or pausing when passing through the target location (Fig. 2 B). This resulted in a significantly lower reward rate (Fig. 2 E), indicating a marked impairment in the spatial cognitive abilities. Mice administered MK-801 still consumed the reward promptly after earning it, indicating no changes in motivation. MK-801 activated dCA1 neurons involved in the VSL task Previous studies have demonstrated the critical role of neuronal activity in the hippocampal dCA1 area in spatial cognitive functions. To further explore the relationship between dCA1 neuronal activity and the VSL task, we examined the expression of the immediate early gene c-Fos in FosTRAP mice after VSL task. Initially, FosTRAP mice received an intraperitoneal injection of tamoxifen (1 mg/kg); 30 minutes later, a subset performed the VSL task as the experimental group, while another subset did not, serving as the control group. Brain hippocampal tissues were harvested 30 minutes later for slicing and immunofluorescent staining (Fig. 3 A and B). Results showed a significantly higher number of c-Fos + cells in the dCA1 area of the experimental group, corroborating hippocampal engagement during navigation in VSL task (Fig. 3 C). To investigate whether MK-801 affects dCA1 neuronal activity related to the VSL task, we first administered tamoxifen to FosTRAP mice, followed by VSL task performance 30 minutes later to mark hippocampal c-Fos + cells with red fluorescence. After three days, mice were injected with either MK-801 or saline, and hippocampal brain tissue was harvested 30 minutes later for green fluorescent staining of c-Fos + cells (Fig. 3 D). In mice injected with MK-801, some neurons displayed green and red fluorescence, appearing yellow after merged (Fig. 3 E). In contrast, in mice injected with saline, no dCA1 neurons were marked with green fluorescence (Fig. 3 F). This consequence indicated a direct impact of MK-801 on dCA1 neurons associated with the VSL task. Effect of MK-801 on Calcium activity of dCA1 neurons during VSL task To characterize the activity pattern of dCA1 neurons when mice perform the VSL task, we conducted craniotomy and microinjected rAAV-CaMKII-GCaMP6s virus into the hippocampus dCA1. Three weeks later, neuronal calcium activity was detected via in vivo fluorescent microscopy, enabling observation of the real-time changes in neuronal activity during the task. (Fig. 4 A). Figure 4 B displays an example of calcium imaging consequence in the hippocampal dCA1 area during the VSL task. Using the Python-based suite2p toolkit, we identified and analyzed the calcium activity signals of individual neurons (Fig. 4 B and C). Figure 4 D further illustrates representative calcium activity of dCA1 neurons throughout the whole VSL task. As noted, MK-801-treated mice completed more trials but spent less time in the target area, showing intensified calcium signals. Using a threshold of mean plus standard deviation, we identified calcium transient peaks and observed significant increases in their frequency, amplitude, and half-width in MK-801-treated mice (Fig. 4 E-G). The correlation of neuronal population activity can help us better understand neural networks. Figure 4 H illustrates the representative result of correlation coefficients between the calcium activity signals of any two neurons in the hippocampal dCA1 area of the same mouse. Heatmap results show a significant decrease in neuronal population correlation in the MK-801 group. The average cumulative distribution curve of these correlation coefficients derived from six mice (Fig. 4 I) indicated a significant reduction in the correlation of neuronal calcium activities in MK-801-treated mice. These results suggested that the disrupted neurons' activity and connectivity may account for spatial cognitive deficits in SZ mice. Following analysis of spontaneous neuronal activity, we examined task-related spatial encoding. We calculated the place fields which reflect the spatial response range of neurons (Fig. 4 J). The place field width was significantly larger in MK-801-treated mice than in control (Fig. 4 K), suggesting reduced spatial specificity of dCA1 neurons. MK-801 impaired the spatial encoding precision of dCA1 neurons, diminishing the mice's ability to integrate spatial information. We also analyzed the population calcium activity pre- and post-reward (Fig. 4 L). Neurons were classified as reward-excited (23% of cells; increased post-reward activity), reward-inhibited (32%; decreased activity), or reward-neutral (45%; unchanged). By comparing the probability distribution of the Reward Preference Index [RPI = (post-reward - pre-reward) / (post-reward + pre-reward)] between these two groups of neurons (Fig. 4 M). more neurons in the MK-801 group showed no significant changes in activity pre and post the reward. MK-801 administration shifted RPI distributions toward neutrality, concurrently reducing proportions of both reward-excited (15% vs. 23% in controls; p < 0.01) and reward-inhibited neurons (16% vs. 32%; p < 0.05; Fig. 4 N), indicating disrupted integration of spatial and reward information. ARI Reverses MK-801-Induced Neuronal and Spatial Cognitive Deficits To assess ARI’s therapeutic potential, mice received MK-801 or saline, followed 30 min later by ARI or saline. Behavioral testing commenced 30 min post-second injection. The results showed no difference in behavioral performance between the ARI + Saline group and the Saline + Saline group (Fig. 5 B-D). As described previously, MK-801 + Saline group mice compared to the Saline + Saline group exhibited increased running distance and speed, with a decrease in success rate (Fig. 5 B-D). However, the running distance and speed for mice in the MK-801 + ARI group were reduced compared to the MK-801 + Saline group (Fig. 5 B-C) and the reward rates increased (Fig. 5 D). Intraperitoneal injection of Saline followed by ARI had little impact on the frequency, amplitude, and half-width of neuronal calcium transients. However, ARI significantly reduced the abnormal increases in these parameters caused by MK-801 injection (Fig. 5 E-G). ARI also partially restored the correlation between calcium activity signals in neurons of MK-801 treated mice (Fig. 5 H). Furthermore, ARI reduced the width of the place fields in the dCA1 neurons of MK-801treated mice (Fig. 5 I), increased the proportion of reward-preferred neurons, and enhanced neuronal reward preference (Fig. 5 J). ARI can correct abnormalities in excitatory activity of dCA1 neurons induced by MK-801 injection, enhancing the neurons' ability to encode spatial positioning and reward information, thereby alleviating spatial cognitive impairments. Discussion In this study, we investigated the relationship between spatial cognitive deficits and hippocampal hyperexcitability in a schizophrenia-relevant model using MK-801-treated mice. Our multimodal approach combined the virtual spatial location (VSL) task with in vivo calcium imaging to characterize dorsolateral CA1 (dCA1) neural circuit dysfunction and evaluate the therapeutic efficacy of aripiprazole (ARI). Behavioral consequences revealed MK-801-induced hyperlocomotion and impaired spatial navigation, similar to the behaviors observed in patients with SZ. Cellular-level analysis demonstrated pathological hyperactivity in dCA1 neurons, manifesting as dysregulated calcium signaling dynamics (increased frequency, amplitude, and half-peak width) accompanied by desynchronized network activity, which diminished the accuracy of spatial and reward information encoding. Furthermore, ARI treatment effectively corrected these abnormalities in dCA1 neuron activity, reducing spontaneous movement and alleviating spatial cognitive impairments. These findings enhance our understanding of the neural mechanisms underlying spatial cognitive impairments in SZ and provide experimental evidence supporting clinical treatment. Previous studies have shown that acute low-dose MK-801 injection leads to increased spontaneous movement and cognitive impairments in mice during Morris water maze and Y-maze tasks [ 25 , 26 ] , establishing links between NMDAR hypofunction and SZ-related spatial cognitive impairment [ 27 ] . However, few experiments simultaneously recorded neuronal activity and assessed spatial cognition performance. We developed a head-fixed mouse VSL task where mice identify reward-related virtual spatial areas and stay in them to get water rewards. To address this gap, we monitored the excitatory calcium activity of hippocampal dCA1 neurons using in vivo calcium imaging. Our results showed that mice treated with acute MK-801 displayed increased spontaneous movement and impaired spatial recognition, confirming the task's effectiveness in detecting spatial cognitive impairments and related neuronal activity abnormalities in SZ. The hippocampus serves as a critical neural substrate for learning and memory [ 28 ] . The dCA1 region, receiving inputs from the entorhinal cortex and CA3 [ 29 ] , functions as a principal hippocampal hub for contextual information integration. Our brain slice immunofluorescence analyses revealed increased c-Fos expression in post-task dCA1 neurons, with MK-801 administration reactivating neurons originally expressing c-Fos during VSL task performance. This demonstrates that spatial cognition-related neural activity can be directly modulated by NMDAR blockade. Complementing previous observations of epileptiform spike-wave discharges and diminished inter-hippocampal synchrony in dCA1 neurons of neonatal hippocampal lesion SZ models [ 30 ] . Similarly, our results showed increased frequency, amplitude, and half-peak width of calcium transients, and a decrease in the synchrony across neurons. Thus, MK-801 induced abnormal excitatory activity in dCA1 neurons, while reduced the coordination among neurons. These findings indicate that NMDAR hypofunction induces both hyperexcitability and impaired interneuronal coordination in dCA1 circuits. Collectively, disrupted neuronal communication in SZ may underlie deficits in spatial information encoding and memory consolidation processes. The hippocampal dCA1 region contains place cells critical for spatial cognition, encoding discrete spatial locations through well-defined place fields [ 31 ] . Studies involving olfactory-based spatial navigation tasks revealed that mice with narrower place fields in the dCA1 region exhibited higher precision in spatial encoding, which correlated with an improvement of performance in goal-directed spatial tasks [ 32 ] . Our results showed that dCA1 neurons in control mice were selectively activated at specific spatial locations, forming clear place fields. In contrast, MK-801-treated mice exhibited broader place fields, indicating reduced spatial encoding precision. Impaired dCA1 place cells may hinder the hippocampal network's ability to differentiate spatial contexts. This impairment may be caused by damage to synaptic plasticity or reduced coordination among neurons, both of which are critical for encoding and retrieving spatial memories [ 33 , 34 ] . This question remains to be analyzed in future studies whether this impairment is specifically due to synaptic abnormalities, network dysfunction, or a combination of both. Due to the increased speed in SZ model mice, the enlargement of place fields in place cells may potentially be attributed to the increase in speed. Previous study has suggested that a small subset of place cells exhibit speed-modulated firing rates [ 35 ] . Since hyperactivity and spatial cognitive impairment are comorbid in SZ patients and interlinked in animal models, there is currently no effective method to validate whether the increase in speed and the widening of place fields are separate. Previous studies also suggest hippocampal dCA1 area, might process and store reward information [ 36 ] . These neurons may show increased activity during reward-related stimuli or exploring reward-associated spaces, helping animals remember reward-relevant details like location or context [ 37 ] . In spatial navigation task, the intensity and proportion of hippocampal dCA1 reward-responsive neurons correlated with successful task completion, reflecting robust reward-related information encoding [ 38 ] . In this study, we also found enhanced or diminished calcium transient activity in normal dCA1 neurons upon entering reward zones, indicating their involvement in processing reward information. In mice treated with MK-801, our results indicated a reduced proportion of reward-associated neurons within the hippocampus, alongside attenuated responses to reward stimuli. These findings suggest a compromised capacity for encoding reward information in the hippocampal region. Consequently, this impairment disrupts the effective integration of spatial and reward information, which is crucial for accurately navigating and performing in VSL task. This deficit in integrating key cognitive components highlights the critical role of hippocampal functionality in complex behavioral tasks reliant on both spatial and reward cues. Aripiprazole (ARI), an atypical antipsychotic, acts as a partial agonist at dopamine D2 receptors and 5-HT1A receptors, and as an antagonist at 5-HT2A receptors [ 39 ] . Excessive dopamine activity in the mesolimbic system is closely associated with positive symptoms. Conversely, reduced dopamine activity in the prefrontal cortex may contribute to negative symptoms [ 22 ] . While ARI effectively treats the positive and negative symptoms of SZ, its impact on cognitive symptoms remains unclear. Previous studies indicated that ARI could alleviate spatial cognitive impairments in preclinical SZ models during water maze [ 38 ] . Our study found that ARI reduced the frequency, amplitude, and half-peak width of calcium transients in the dCA1 neurons of MK-801-treated mice, increased the synchronization of neuronal activity, narrowed place fields, and improved the proportion and response strength of reward-reactive neurons. ARI treatment also mitigated MK-801-induced hyper locomotion and improved the accuracy of spatial recognition in VSL tasks, suggesting that ARI might alleviated cognitive disorders by correcting abnormal neuronal activities in dCA1. In conclusion, our study revealed that MK-801-induced spatial cognition impairments in mice are associated with reduced neuronal synchronization and encoding accuracy of spatial and reward information in hippocampal dCA1 neurons. Moreover, ARI showed potential therapeutic effects in restoring neuronal function and improving spatial cognition. These findings advance our understanding of SZ pathophysiology and underscore hippocampal circuit modulation as a strategic target for cognitive therapeutics. Declarations Competing interests The authors declare no competing interests. Author Contributions Ling Qin and Pingting Yang conceptualized, designed and supervised the studies. Zijie Li and Xueru Wang set up the experiment equipments and analyzed the results. Xueying Yang, Xuejiao Wang and Huangyu Wang performed the experiments. Zijie Li, Xueying Yang and Ling Qin drafted the paper. All authors have read and approved the paper. Acknowledgements The study was funded by the Chinese National Key Technology R&D Program (2021YFC2501303 to PTY), the Joint Funds of the National Natural Science Foundation of China (U22A20309 to PTY), the Department of Science and Technology of Liaoning Province (2021JH1/10400049 to LQ), the 'Xingliao Talent Plan' of Liaoning Province (XLYC2002094 to LQ), National Natural Science Foundation of China (Youth Fund, No.82301533 to XJW). References O'Keefe J, Dostrovsky J. The hippocampus as a spatial map. Preliminary evidence from unit activity in the freely-moving rat. Brain Res. 1971. 34(1): 171–5. Batinic B. Cognitive Models of Positive and Negative Symptoms of Schizophrenia and Implications for Treatment. Psychiatr Danub. 2019. 31(Suppl 2): 181–184. Guo JY, Ragland JD, Carter CS. Memory and cognition in schizophrenia. Mol Psychiatry. 2019. 24(5): 633–642. Morris RG, Garrud P, Rawlins JN, O'Keefe J. Place navigation impaired in rats with hippocampal lesions. 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Soltanian-Zadeh S, Sahingur K, Blau S, Gong Y, Farsiu S. Fast and robust active neuron segmentation in two-photon calcium imaging using spatiotemporal deep learning. Proc Natl Acad Sci U S A. 2019. 116(17): 8554–8563. Jun H, Bramian A, Soma S, Saito T, Saido TC, Igarashi KM. Disrupted Place Cell Remapping and Impaired Grid Cells in a Knockin Model of Alzheimer's Disease. Neuron. 2020. 107(6): 1095–1112.e6. Chen TW, Wardill TJ, Sun Y, et al. Ultrasensitive fluorescent proteins for imaging neuronal activity. Nature. 2013. 499(7458): 295–300. Machado ML, Lefèvre N, Philoxene B, et al. New software dedicated to virtual mazes for human cognitive investigations. J Neurosci Methods. 2019. 327: 108388. Packer AM, Russell LE, Dalgleish HW, Häusser M. Simultaneous all-optical manipulation and recording of neural circuit activity with cellular resolution in vivo. Nat Methods. 2015. 12(2): 140–6. Dombeck DA, Harvey CD, Tian L, Looger LL, Tank DW. Functional imaging of hippocampal place cells at cellular resolution during virtual navigation. Nat Neurosci. 2010. 13(11): 1433–40. Burris KD, Molski TF, Xu C, et al. Aripiprazole, a novel antipsychotic, is a high-affinity partial agonist at human dopamine D2 receptors. J Pharmacol Exp Ther. 2002. 302(1): 381–9. Orzelska-Górka J, Mikulska J, Wiszniewska A, Biała G. New Atypical Antipsychotics in the Treatment of Schizophrenia and Depression. Int J Mol Sci. 2022. 23(18). Stępnicki P, Kondej M, Kaczor AA. Current Concepts and Treatments of Schizophrenia. Molecules. 2018. 23(8). Cui K, Yu Z, Xu L, et al. Behavioral features and disorganization of oscillatory activity in C57BL/6J mice after acute low dose MK-801 administration. Front Neurosci. 2022. 16: 1001869. Xu L, Qiu X, Wang S, Wang Q, Zhao XL. NMDA Receptor Antagonist MK801 Protects Against 1-Bromopropane-Induced Cognitive Dysfunction. Neurosci Bull. 2019. 35(2): 347–361. Kocsis B. Differential role of NR2A and NR2B subunits in N-methyl-D-aspartate receptor antagonist-induced aberrant cortical gamma oscillations. Biol Psychiatry. 2012. 71(11): 987–95. Pettit NL, Yap EL, Greenberg ME, Harvey CD. Fos ensembles encode and shape stable spatial maps in the hippocampus. Nature. 2022. 609(7926): 327–334. Li Y, Xu J, Liu Y, et al. A distinct entorhinal cortex to hippocampal CA1 direct circuit for olfactory associative learning. Nat Neurosci. 2017. 20(4): 559–570. Lee H, Dvorak D, Fenton AA. Targeting Neural Synchrony Deficits is Sufficient to Improve Cognition in a Schizophrenia-Related Neurodevelopmental Model. Front Psychiatry. 2014. 5: 15. Xu H, Baracskay P, O'Neill J, Csicsvari J. Assembly Responses of Hippocampal CA1 Place Cells Predict Learned Behavior in Goal-Directed Spatial Tasks on the Radial Eight-Arm Maze. Neuron. 2019. 101(1): 119–132.e4. Radvansky BA, Dombeck DA. An olfactory virtual reality system for mice. Nat Commun. 2018. 9(1): 839. Su J, Huang F, Tian Y, et al. Entorhinohippocampal cholecystokinin modulates spatial learning by facilitating neuroplasticity of hippocampal CA3-CA1 synapses. Cell Rep. 2023. 42(12): 113467. Wang C, Yang H, Chen S, Wang C, Chen X. Early and late place cells during postnatal development of the hippocampus. Nat Commun. 2024. 15(1): 10075. McClain K, Tingley D, Heeger DJ, Buzsáki G. Position-theta-phase model of hippocampal place cell activity applied to quantification of running speed modulation of firing rate. Proc Natl Acad Sci U S A. 2019. 116(52): 27035–27042. Wikenheiser AM, Marrero-Garcia Y, Schoenbaum G. Suppression of Ventral Hippocampal Output Impairs Integrated Orbitofrontal Encoding of Task Structure. Neuron. 2017. 95(5): 1197–1207.e3. Biane JS, Ladow MA, Stefanini F, et al. Neural dynamics underlying associative learning in the dorsal and ventral hippocampus. Nat Neurosci. 2023. 26(5): 798–809. Zohny SM, Habib MZ, Mohamad MI, et al. Memantine/Aripiprazole Combination Alleviates Cognitive Dysfunction in Valproic Acid Rat Model of Autism: Hippocampal CREB/BDNF Signaling and Glutamate Homeostasis. Neurotherapeutics. 2023. 20(2): 464–483. DeLeon A, Patel NC, Crismon ML. Aripiprazole: a comprehensive review of its pharmacology, clinical efficacy, and tolerability. Clin Ther. 2004. 26(5): 649–66. Additional Declarations The authors have declared there is NO conflict of interest to disclose Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6252679","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":434713170,"identity":"12b1138b-bf13-40d7-ae7d-5430834ce5e9","order_by":0,"name":"Ling Qin","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA40lEQVRIie3RvQrCMBDA8auBuJzt2qDUV6j0hexiFzfBxQ8EoW7OLr6Do2MgUJeCmwh1MApODk6ii5hS55pRMH+47X6EcAAm0y9GwOJtgAYFsI4AXItATlAR4usRKNZQDXW1iL2pcS7XI7Trs90AhwfPASJP+xLChN3mYbpB2kj7GSaXgE1oEHRLiC/Q52GcIHW7nQypCFccaV2b9PClT4aKRAmpxRqEFYTnrxC2nIuATb/8xd6mLfmMx15zEcnb9S48pzqV5zLyOYRQg34lv05+3PIKMlZTPVqPb9smk8n0l70BhMFPeDSaSZcAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0001-8717-3833","institution":"China Medical University","correspondingAuthor":true,"prefix":"","firstName":"Ling","middleName":"","lastName":"Qin","suffix":""},{"id":434713174,"identity":"3dd807c7-1cde-4af0-b64d-0b5cd3b6b289","order_by":1,"name":"Zijie Li","email":"","orcid":"","institution":"China Medical University","correspondingAuthor":false,"prefix":"","firstName":"Zijie","middleName":"","lastName":"Li","suffix":""},{"id":434713175,"identity":"90cb2c4e-5129-483b-a4d6-53d8f57c2a2d","order_by":2,"name":"Xueying Yang","email":"","orcid":"","institution":"China Medical University","correspondingAuthor":false,"prefix":"","firstName":"Xueying","middleName":"","lastName":"Yang","suffix":""},{"id":434713176,"identity":"b31d7593-fc1c-4855-aaed-5a457c5458bd","order_by":3,"name":"Xueru Wang","email":"","orcid":"","institution":"China Medical University","correspondingAuthor":false,"prefix":"","firstName":"Xueru","middleName":"","lastName":"Wang","suffix":""},{"id":434713177,"identity":"1a45bb1a-dbfc-4fe4-bbb9-6a41b5843709","order_by":4,"name":"Xuejiao Wang","email":"","orcid":"","institution":"China Medical University","correspondingAuthor":false,"prefix":"","firstName":"Xuejiao","middleName":"","lastName":"Wang","suffix":""},{"id":434713178,"identity":"2bf17923-144f-47b4-856e-bdefac2565dc","order_by":5,"name":"Huangyu Wang","email":"","orcid":"","institution":"China Medical University","correspondingAuthor":false,"prefix":"","firstName":"Huangyu","middleName":"","lastName":"Wang","suffix":""},{"id":434713179,"identity":"b8d14ead-972b-4953-aab5-66eed8cfb08c","order_by":6,"name":"Pingtging Yang","email":"","orcid":"","institution":"China Medical University","correspondingAuthor":false,"prefix":"","firstName":"Pingtging","middleName":"","lastName":"Yang","suffix":""}],"badges":[],"createdAt":"2025-03-18 11:36:41","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6252679/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6252679/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":80710976,"identity":"9deec9a0-857e-4796-813f-1582ce3d1398","added_by":"auto","created_at":"2025-04-16 09:04:46","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":3761198,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDesign of the VSL Task and Mouse Behavior During the VSL Task\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA: Schematic representation of a head-fixed mouse performing a behavioral task in a VR setting.\u003c/p\u003e\n\u003cp\u003eB: Diagrams illustrating two different training phases. In the non-delayed phase, mice receive a water reward immediately upon entering the target area. In the delayed phase, mice must remain in the target area for 1.5 seconds before receiving a water reward.\u003c/p\u003e\n\u003cp\u003eC: Training position trajectories and movement speeds of mice at the start (left panel), end (middle panel) of the non-delayed phase, and middle of the delayed phase (right panel). Position trajectory (upper panel) displays the position of the mouse on the virtual track. Speed curve (lower panel)show the average speed of the mouse on the virtual track.\u003c/p\u003e\n\u003cp\u003eD-F: Changes in total movement distance (D), average speed before entering the target area (E), and reward acquisition rate (F) across different sessions in both non-delayed and delayed phase.\u003c/p\u003e","description":"","filename":"figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6252679/v1/440023775da28dcd6c2b1e7f.jpg"},{"id":80709708,"identity":"8c54f3a7-9590-4491-ba4a-737a8de4024a","added_by":"auto","created_at":"2025-04-16 08:56:46","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2739740,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eBehavioral Abnormalities of MK-801-treated mice in the VSL Task\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA: Flowchart of mouse injection procedure.\u003c/p\u003e\n\u003cp\u003eB: Position trajectories (upper panel) and speeds (lower panel) of Saline and MK-801-treated mice during the VSL task.\u003c/p\u003e\n\u003cp\u003eC-E: Comparative analysis for movement distance (C), average speed before entering the target area (D) and success rate (E) between Saline and MK-801-treated mice. Paired t test, df=7. Distance: p\u0026lt;0.001, t=27.05. Speed: p\u0026lt;0.001, t=7.894. Success rate: p\u0026lt;0.001, t=8.057.\u003c/p\u003e","description":"","filename":"figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6252679/v1/faeabb05780ec59f448c8b11.jpg"},{"id":80709700,"identity":"77cd8910-3f5f-41f5-a698-c0b73f9b85a3","added_by":"auto","created_at":"2025-04-16 08:56:46","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":4094785,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003edCA1 place cells activated in task can be reactivated by Mk-801\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA: Flowchart illustrating the hippocampal slicing and fluorescent immunostaining process post-VSL task.\u003c/p\u003e\n\u003cp\u003eB: c-Fos expression in the hippocampal dCA1 area of mice involved or non-involved in the task.\u003c/p\u003e\n\u003cp\u003eC: Statistical graph comparing the hippocampal c-Fos expression of involved and non-involved mice. Unpaired t test, df=12, p\u0026lt;0.001, t=10.64.\u003c/p\u003e\n\u003cp\u003eD: Flowchart illustrating the hippocampal slicing and fluorescent immunostaining process post-VSL task and MK-801-injection.\u003c/p\u003e\n\u003cp\u003eE: c-Fos expression in the hippocampal dCA1 region of mice injected with saline or MK-801 after task completion.\u003c/p\u003e\n\u003cp\u003eF: Statistical graph comparing the hippocampal c-Fos expression of mice received saline or MK-801- injection. Unpaired t test with Welch's correction, df=7.085, p\u0026lt;0.001, t=39.36.\u003c/p\u003e","description":"","filename":"figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6252679/v1/51297d253d3d9d065735c07f.jpg"},{"id":80712084,"identity":"86c7d801-2c3b-41e8-965d-439ee27b0348","added_by":"auto","created_at":"2025-04-16 09:12:46","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":16687374,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eMK-801 impaired the spatial encoding ability of the dCA1 neurons.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA: Schematic of simultaneous neuronal calcium recording when mice performing the VSL task.\u003c/p\u003e\n\u003cp\u003eB: Representative consequence of in vivo fluorescence microscopy of hippocampal dCA1 neurons (left panel) and individual neurons identified by suite2P (right panel).\u003c/p\u003e\n\u003cp\u003eC: Examples of calcium activity of dCA1 neurons after mice were injected saline or MK-801. The blue line represents calcium activity, and the black dots indicate peaks of calcium activity.\u003c/p\u003e\n\u003cp\u003eD: Calcium activity signals of dCA1 neuron population during one recording session of the VSL task. The colors in the heatmap represent calcium activity intensity, with brighter colors indicating higher activity levels.\u003c/p\u003e\n\u003cp\u003eE-G: Violin plots of frequency (E), amplitude (F), and half-width (G) of the calcium fluorescence signal for Saline and MK-801-treated mice. Data was collected from 7 mice per group, 5325 neurons recorded in Saline group and 5189 neurons recorded in Mk-801 group. Wilcoxon rank-sum test was used for E-G. Frequency: p\u0026lt;0.001. Amplitude: p\u0026lt;0.001. Half-width: p\u0026lt;0.001.\u003c/p\u003e\n\u003cp\u003eH: Representative results of the Pearson’s correlation coefficients between pairs of neurons for Saline and MK-801-treated mice (n=800).\u003c/p\u003e\n\u003cp\u003eI: Averaged cumulative distribution curve of correlation coefficients for Saline and MK-801-treated mice (n=7). Kolmogorov-Smirnov test, p\u0026lt;0.001.\u003c/p\u003e\n\u003cp\u003eJ: Spatial firing rate maps for the 612 place cells on the VR track. Each row is a single neuron. Place field (dark area) was aligned along the track position.\u003c/p\u003e\n\u003cp\u003eK: Violin plot of the width of neuronal place field in saline and MK-801-treated mice. Data was collected from 7 mice per group, 4125 neurons recorded in Saline group and 4094 neurons recorded in Mk-801 group. Only place cells were involved. \u0026nbsp;Wilcoxon rank-sum test, p\u0026lt;0.001.\u003c/p\u003e\n\u003cp\u003eL: Changes of individual neuronal calcium activities before and after reward time (red line). Two horizontal lines mark the boundaries of the neurons positively (top section) and negatively (bottom section) modulated by reward respectively.\u003c/p\u003e\n\u003cp\u003eM: Probability distribution curves of the reward preference index among the dCA1 neurons of saline and MK-801-treared mice. Wilcoxon rank-sum test, p\u0026lt;0.001.\u003c/p\u003e\n\u003cp\u003eN: Pie charts showed the proportion of reward-related neurons. Chi-square test, p=0.002.\u003c/p\u003e","description":"","filename":"figure4.png","url":"https://assets-eu.researchsquare.com/files/rs-6252679/v1/c460404a5fa82e016757cb88.png"},{"id":80710980,"identity":"306ebd68-6a40-4230-8552-e7d06bdfafdd","added_by":"auto","created_at":"2025-04-16 09:04:46","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":4538656,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eARI ameliorates MK-801 induced behavioral and neuronal activity abnormalities\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA\u003cstrong\u003e: \u003c/strong\u003eLocation trajectories (upper panel) and speed curves (bottom panel) of a representative mouse in the Saline+ARI, MK-801+Saline and MK-801+ARI group.\u003c/p\u003e\n\u003cp\u003eB-D: Total movement distances (B), speed (C) and rewarded rate (D) in the mice of different groups. Data from 8 mice per group are shown as the mean+ sem. Kruskal-Wallis test followed by Sidak multiple comparison. Distance: F (3, 28) = 73.15. Speed: F (3, 28) = 44.85. Rewarded rate: F (3, 28) = 65.55.\u003c/p\u003e\n\u003cp\u003eE-G: Violin plots of frequency, amplitude, and half-width of neuronal calcium activity in the mice of different groups. Data was collected from 8 mice per group, 5980 neurons recorded in Saline+saline group, 6015 neurons recorded in Saline+ARI group, 6124 neurons recorded in MK-801+saline group, and 5783 neurons recorded in MK-801+ARI group. Kruskal-Wallis test followed by Sidak multiple comparison. Frequency: F (3, 23902) = 612.7. Amplitude: F (3, 23902) = 158.9. Half-width: F (3, 23902) = 163.5.\u003c/p\u003e\n\u003cp\u003eH: Cumulative distribution curves of the correlation coefficients between the individual neuronal calcium activities in the mice of different groups.\u003c/p\u003e\n\u003cp\u003eI: Violin plot of the width of place field in the mice of different groups. 3848 neurons recorded in Saline+saline group, 4151 neurons recorded in Saline+ARI group, 4221 neurons recorded in MK-801+saline group, and 3944 neurons recorded in MK-801+ARI group. Only place cells were involved. Kruskal-Wallis test followed by Sidak multiple comparison. F (3, 16160) = 594.5.\u003c/p\u003e\n\u003cp\u003eJ: Probability distribution curves of the reward preference index in the mice of different groups.\u003c/p\u003e","description":"","filename":"figure5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6252679/v1/c681df4126f2f3d80dd94a99.jpg"},{"id":85548951,"identity":"68c0e2a9-327e-4f07-bc7e-cdb7213ac2ee","added_by":"auto","created_at":"2025-06-27 09:21:20","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":20188594,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6252679/v1/b5546075-d734-4b8c-a8b5-824982e05e4e.pdf"}],"financialInterests":"The authors have declared there is \u003cb\u003eNO\u003c/b\u003e conflict of interest to disclose","formattedTitle":"Correlation between abnormal hippocampal neural activities and spatial cognitive impairments in the model mice of schizophrenia and therapeutic effects of aripiprazole","fulltext":[{"header":"Introduction","content":"\u003cp\u003eSpatial cognition, a core component of cognitive function, enables animals to perceive spatial information in environment and integrate it into a complete cognitive map \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. Schizophrenia (SZ) is a prevalent mental disorder characterized primarily by positive symptoms, negative symptoms, and cognitive impairments \u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]\u003c/sup\u003e. Spatial cognition impairment, a common aspect of cognitive dysfunction found in SZ patients, manifests in patients often struggle with self-localization and environmental navigation, \u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. Previous studies have reported the hippocampal dorsal CA1 (dCA1) serving as a key brain area for spatial cognition function \u003csup\u003e[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e. The majority of excitatory hippocampal neurons have stable and location-based receptive fields (place fields). These cells called place cell can encode and retrieval spatial information \u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. Clinical studies have shown that hippocampal damage typically results significant impairments in spatial cognition and memory \u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. In patients with SZ, dCA1 atrophy and decreased density of dendritic spines have been observed \u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e. Hippocampal structural lesions appear in the early stages of schizophrenia, suggesting that these symptoms are not secondary to schizophrenia or treatment measures. Neuropharmacological research has also found the level of excitatory neurotransmitter glutamate is abnormally elevated \u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. Additionally, further research has found that patients with SZ have weakened functional connections with upstream brain areas such as the anterior cingulate cortex and the entorhinal cortex \u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]\u003c/sup\u003e. This is compounded by reduced neuroplasticity in the dCA1, which likely underlies persistent cognitive impairments \u003csup\u003e[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eWhile current evidence has demonstrated the presence of spatial cognition impairments in SZ patients and the associated structural and functional abnormalities in the hippocampal dCA1 area, the causal relationship between these abnormalities remains unclear. To address this issue, selecting appropriate SZ animal models for in vivo neurophysiological studies is particularly crucial. Pharmacological and genetic evidence implicates NMDA receptor (NMDAR) hypofunction as key characteristic of SZ pathophysiology \u003csup\u003e[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e. The application of NMDAR antagonists like dizocilpine (MK-801) can induce cognitive and behavioral impairments similar to those observed in SZ patients \u003csup\u003e[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]\u003c/sup\u003e. Many studies have shown that MK-801 damages spatial memory in the Morris water maze and radial-arm maze \u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. However, the absence of direct hippocampal neuronal recordings in SZ model mice has prevented definitive conclusions about whether dCA1 neuronal dysfunction drives observed behavioral impairments. To address this gap, it is necessary to perform in vivo recordings of the dynamic activity of individual hippocampal neurons while SZ model mice undertake spatial cognitive tasks.\u003c/p\u003e \u003cp\u003eRecent researches in recording hippocampal neuronal activity have used large view calcium imaging as a novel methodology \u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. This technique allows monitoring hundreds of neurons simultaneously and recording specific cell subtypes labeled with calcium indicators driven by promoters such as Thy1 or Camk2 \u003csup\u003e[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]\u003c/sup\u003e. Compared with electrophysiological recording, large view calcium imaging might be less affected by movements \u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e. Large view calcium imaging enables the simultaneous recording of both the precise firing times and spatial locations, thereby providing a better understanding of the relationship between hippocampal neural activity and spatial cognitive function.\u003c/p\u003e \u003cp\u003eBecause large view calcium imaging requires the use of a large objective lens, the mice need to be head-fixed under the objective lens. In order to detect their hippocampus-related spatial cognitive ability \u003csup\u003e[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]\u003c/sup\u003e, previous studies have used virtual reality (VR) technology to ensure real-time synchronization between the virtual environment and the mouse's running on a treadmill \u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. In this study, we combined the virtual spatial location (VSL) task and calcium imaging recording in hippocampus, in order to explore the correlation between abnormal activity of dCA1 place cell and spatial cognition impairments in the SZ mouse model.\u003c/p\u003e \u003cp\u003eSchizophrenia is often associated with abnormal levels of dopamine \u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. Beyond mechanistic insights, this study explores dopamine modulation as a potential therapeutic strategy. Aripiprazole (ARI) can partially activate dopamine D2 receptors, and stabilize dopamine function \u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e. ARI has been proven to alleviate the positive and negative symptoms of SZ \u003csup\u003e[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]\u003c/sup\u003e, its effects on correcting abnormal hippocampal neuronal activity and potential impacts on spatial cognition impairments remain unclear.\u003c/p\u003e \u003cp\u003eThough ARI alleviates positive and negative symptoms [23, 24], its effects on correcting dCA1 neuronal dysfunction and spatial cognition deficits is unknown. Therefore, we evaluated the potential therapeutic effects of ARI. The results of this study will provide critical evidence for refining treatment strategies targeting cognitive impairments in SZ.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eAnimals\u003c/h2\u003e \u003cp\u003eIn this study, we selected C57BL/6 mice aged 6\u0026ndash;8 weeks, weighing between 30\u0026ndash;40 g, from Vital River Laboratories in China. Additionally, we used FosCreER mice [B6.129(Cg)-Fostm1.1(cre/ERT2)Luo/J, #021882, Jackson Laboratories, USA] and Ai14 mice [B6.Cg-Gt(ROSA)26Sortm14(CAG-tdTomato)Hze/J, #007914, Jackson Laboratories, USA]. FosTRAP mice were obtained by breeding female Ai14 mice with male FosCreER mice. All experimental animals were maintained and bred to meet the following conditions: an environmental temperature of 22\u0026ndash;24\u0026deg;C, humidity levels between 50\u0026ndash;55%, ensuring a 12-hour light/dark cycle. Animal care strictly followed the policies and procedures outlined in the \"Guide for the Care and Use of Laboratory Animals\" published by the National Institutes of Health (NIH), USA. All related procedures were approved by the Animal Ethics Committee of China Medical University (CEUA). All surgical operations were performed under complete anesthesia to minimize pain and reduce the number of animals used as much as possible.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eViral Injection\u003c/h3\u003e\n\u003cp\u003eAnesthesia was induced using isoflurane at a concentration of 4\u0026ndash;5%, and once the mice no longer responded to nociceptive stimuli, anesthesia was maintained with 2% isoflurane. Throughout the surgical procedure, body temperature was monitored and maintained at approximately 37\u0026deg;C using a thermostatic electric heating blanket. After securing the mouse\u0026lsquo;s head in a stereotaxic apparatus, the head skin was disinfected with 75% alcohol. Under a stereomicroscope, the skin was incised to fully expose the skull and fontanelle. Based on the Paxinos \u0026amp; Watson brain atlas, the hippocampal dCA1 area (AP: -2.0 mm, ML: 2.0 mm) was marked with a pencil. At the specified coordinates, a 0.5 mm diameter drill bit rotating at 4,000 rpm was used to open the skull. Physiological saline was used to irrigate the hole for hemostasis, and the dura mater was pierced under micro forceps. A calcium indicator (rAAV-CaMKII-Gcamp6s) was diluted in physiological saline at a 1:5 ratio and loaded into a microinjector (10 \u0026micro;l) placed in a micropump. Under microscopic guidance, the glass pipette was adjusted to the designated depth(DV: -1.5 mm), and the calcium indicator was slowly injected into the dCA1 region at a rate of 20 nl/min, injecting a total of 200 nl. After the injection, the needle was left in place for 10 minutes to allow for sufficient viral diffusion before it was slowly withdrawn. Seal the injection site with dental cement and then suture the skin.\u003c/p\u003e\n\u003ch3\u003eLens Insertion\u003c/h3\u003e\n\u003cp\u003eTwo weeks following the viral injection, the mice underwent a craniotomy procedure, with anesthesia induction and maintenance consistent with previously described methods. The mouse's head was secured in a stereotaxic device. Using a 0.5 mm drill bit, a circular craniotomy of 4 mm diameter was centered over the coordinates of the dCA1 area. After exposing the cortex above the hippocampus, the brain tissue over the hippocampus (~\u0026thinsp;1mm) was aspirated using a suction device. The site was irrigated with physiological saline to achieve hemostasis, and a metal cannula (sealed at one end with a PVC piece) was implanted into the bone window, then fixed with dental cement. Two screws were inserted posterior to the cranium, Two metal rings with a diameter of 0.2 mm were implanted on both sides of the dental cement for head fixation After the surgery, the mice were allowed to recover consciousness before being transferred to individual cages. The mice were allowed to recover for one week before proceeding with further experimental manipulations.\u003c/p\u003e\n\u003ch3\u003eVirtual spatial location Task\u003c/h3\u003e\n\u003cp\u003eTwo weeks after the surgery, mice equipped with head plates were head-fixed on a turntable. Before the initial training of the virtual spatial location (VSL) task, mice were allowed to run on the turntable for 5\u0026ndash;10 minutes as a habituation phase. This familiarization phase was conducted daily for at least five consecutive days. Prior to the commencement of formal behavioral training, water restriction was enforced for a minimum of 36 hours to ensure that the reward during training effectively motivated the mice to maintain sustained engagement. Additionally, mice were monitored daily for weight and appearance to ensure no behavioral abnormalities during training.\u003c/p\u003e \u003cp\u003eA virtual unidirectional linear track (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB) was created using unity3D. At the start of training, mice were positioned at the origin of the virtual track and then ran from the starting point to the endpoint. The target area was marked on the floor with a mosaic pattern as a cue. The task was divided into non-delayed and delayed phases, requiring different conditions to trigger rewards. During the non-delayed phase, mice received water rewards immediately upon crossing the target areas. During the delay phase, the mice were required to pause in the target area for at least 1.5 seconds to receive a reward. The motion trajectories of the mice on the virtual track were analyzed using a custom Python program based on their positions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eTargeted Recombination in Fos-Active Groups\u003c/h3\u003e\n\u003cp\u003eAfter FosTRAP mice (Fos-CreERT2-Ai14) administered 4-hydroxytamoxifen (4-OHT) drug, task-activated neurons express c-Fos protein and generate Cre recombinase, leading to the expression of red fluorescence (tdTomato). Prior to the commencement of the experiment, preparation of 4-OHT was conducted. 4-OHT was dissolved in ethanol at 37\u0026deg;C with shaking for 15 minutes to achieve a concentration of 20 mg/mL. The 4-OHT solution could be aliquoted and stored at -20\u0026deg;C for up to one month. On the day of use, the 4-OHT was re-dissolved in ethanol by shaking again for 15 minutes at 37\u0026deg;C. Corn oil was then added to adjust the final concentration of the 4-OHT solution to 5 mg/mL, followed by the vacuum centrifugation to evaporate the ethanol.\u003c/p\u003e \u003cp\u003eFosTRAP mice underwent daily intraperitoneal injections of saline for seven consecutive days to minimize the stress response induced by experimental handling. On the eighth day, mice initially received an intraperitoneal injection 4-OHT at a dose of 50 mg/kg. Half an hour later, they were subjected to the VSL task. Three days following this, the mice were administered either saline or MK-801 (0.1 mg/kg). Subsequently, the mice were returned to their cages. 24 hours after these treatments, the mice were euthanized via cardiac perfusion for further collection and sectioning of brain tissue.\u003c/p\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eHistological Sectioning and Immunofluorescence Staining\u003c/h2\u003e \u003cp\u003eThe brains were extracted and fixed in 4% paraformaldehyde for 48 hours, before being transferred to a gradient sucrose solution for dehydration. For cryosectioning, the excess fluid on the brain tissue surface was first removed using filter paper. The brain tissues were then embedded in OCT compound and secured within a cryostat (CM 1900, Leica Biosystems, Germany) at -20\u0026deg;C. Sections of 20 \u0026micro;m thickness were cut from the frozen brain tissues and collected on adhesive slides.\u003c/p\u003e \u003cp\u003eThe cryosections were left at room temperature for 1 hour and then washed with PBS three times, for 5 minutes each. Drops of 10% normal goat serum were applied to the brain slices and incubated at room temperature for 1 hour to block non-specific binding. After absorbing the serum with filter paper, diluted c-Fos antibody (1:5000) was added, and the sections were incubated at 4\u0026deg;C for 12 hours. The brain slices were washed again with PBS three times, for 5 minutes each. A secondary antibody, goat anti-rabbit CoraLite488 (1:300), was applied and the sections were incubated in the dark at room temperature for 2 hours. After additional washing with PBS three times for 5 minutes each, an anti-fade mounting medium was added under dark conditions, followed by covering with a coverslip. Tissue sections were examined under a fluorescence microscope (BX53, Olympus, Japan).\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eCalcium Fluorescence Imaging Recording\u003c/h3\u003e\n\u003cp\u003eThe mouse's head was fixed in place on a turntable to facilitate in vivo calcium fluorescence imaging during running. An induction device was placed parallel over the turntable to detect rotations, capturing motion data, which was then analyzed using a computer to assess the mouse's locomotion. Prior to imaging, mice were allowed to acclimate to the experimental environment for 1 hour, after which imaging commenced. The excitation light of the microscope was set to 485 nm to stimulate the GCaMP6s fluorescent protein, and a custom-built software was used to simultaneously trigger both the turntable and the imaging recording devices. Fluorescence microscopy was employed to capture the dynamic changes in neuronal calcium signaling. To prevent excessive quenching of the fluorescence signal, recording began concurrently with the initiation of the VSL task, with each recording session lasting 15 minutes.\u003c/p\u003e\n\u003ch3\u003eCalcium Imaging Data Analysis\u003c/h3\u003e\n\u003cp\u003eInitially, the ImageJ plugin was utilized to stabilize the imagery, mitigating the effects of motion-induced jitter during recording and facilitating the identification of individual neurons. The Python suite2p toolbox was used to identify and analyze neurons. Calcium signals were expressed as ΔF/F, where the baseline fluorescence (F\u003csub\u003e0\u003c/sub\u003e) was calculated as the mean fluorescence intensity across the entire recording session. The ΔF/F value at each time point was derived from (F(t)\u0026thinsp;\u0026minus;\u0026thinsp;F\u003csub\u003e0\u003c/sub\u003e)/ F\u003csub\u003e0\u003c/sub\u003e, with F(t) being the raw fluorescence signal. We used the \u0026lsquo;find_peak\u0026rsquo; function from the Python scipy package to calculate the frequency and amplitude of neuronal calcium signal activity. Neurons with signal decay exceeding two seconds were excluded using the OASIS toolbox (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://github.com/j-friedrich/OASIS\u003c/span\u003e\u003cspan address=\"https://github.com/j-friedrich/OASIS\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e), as these were considered identification failures, and the half-width of neuronal calcium signal activity was calculated. The correlation coefficient between neuronal calcium signal activities was computed using the \u0026lsquo;corrcoef\u0026rsquo; function from the Python numpy package.\u003c/p\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eStatistical Analysis\u003c/h2\u003e \u003cp\u003eData conforming to a Gaussian distribution was subjected to t-test analysis, or one-way Analysis of Variance (ANOVA) followed by Tukey\u0026rsquo;s multiple comparison tests, the rank sum test was used if data did not conform to Gaussian distribution. Data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;Standard Error of the Mean (SEM).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eTraining and Behavioral Performance of Mice in VSL Tasks\u003c/h2\u003e \u003cp\u003eHead-fixed mice navigated a virtual straight track in a virtual spatial location (VSL) task, with water rewards (~\u0026thinsp;10 \u0026micro;l) delivered upon passing through a predefined target area (mosaic-marked region, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA-B). The VSL task was comprised of non-delayed and delay phases. During the non-delayed phase, mice received reward immediately upon entering the target area, facilitating learning and familiarization with the reward locations in the virtual environment (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB). Initially, the mice ran shorter distances at lower speeds. After 8\u0026ndash;10 days training, both the running distance and speed significantly increased, indicating adaptation to running in the VR environment.\u003c/p\u003e \u003cp\u003eFollowing the non-delayed training, the delay phase began, requiring the mice to pause in the target area for at least 1.5 seconds to receive a reward; if not, no reward was given. Early in the training phase, the mice frequently stopped at incorrect locations or paused too briefly, thereby reducing their chances of obtaining rewards. After 4\u0026ndash;6 days in the delayed training phase, a reduction in running speed at the target areas suggested the mice began to recognize the association between the location and reward (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC) and gradually improving their success rates to stabilize at over 80%. This phenomenon indicated that the mice had formed an association between the location and reward (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eF). Throughout the training, the mice's running distance and speed increased during the non-delayed phase and remained stable upon entering the delayed phase (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD and E). Distance and speed in the late stage of two phases were similar, indicating that the motivation of running behavior in different phase was same. The success rate for obtaining rewards dropped sharply from 100% in the non-delayed phase to about 50% at the start of the delayed phase, then gradually increased and stabilized above 80% as training progressed (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eF).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eMK-801impaired mice\u0026rsquo;s spatial cognitive ability in the VSL Task\u003c/h2\u003e \u003cp\u003eAfter the training of VSL task, mice were intraperitoneal injected with the NMDA receptor antagonist MK-801 at a dose of 0.1 mg/kg before task to serve as experimental group, and saline for the control group. Thirty minutes later, the mice were engaged in the VSL task to assess the impact of MK-801 injection on their spatial cognitive behavior (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). Mice received saline injections (control group) were still able to accurately pause within the target location and obtain rewards. However, following the injection of MK-801, the mice exhibited increased movement speeds (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD) and completed a greater number of trials, without notable deceleration or pausing when passing through the target location (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). This resulted in a significantly lower reward rate (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eE), indicating a marked impairment in the spatial cognitive abilities. Mice administered MK-801 still consumed the reward promptly after earning it, indicating no changes in motivation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003eMK-801 activated dCA1 neurons involved in the VSL task\u003c/h2\u003e \u003cp\u003ePrevious studies have demonstrated the critical role of neuronal activity in the hippocampal dCA1 area in spatial cognitive functions. To further explore the relationship between dCA1 neuronal activity and the VSL task, we examined the expression of the immediate early gene c-Fos in FosTRAP mice after VSL task. Initially, FosTRAP mice received an intraperitoneal injection of tamoxifen (1 mg/kg); 30 minutes later, a subset performed the VSL task as the experimental group, while another subset did not, serving as the control group. Brain hippocampal tissues were harvested 30 minutes later for slicing and immunofluorescent staining (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA and B). Results showed a significantly higher number of c-Fos\u0026thinsp;+\u0026thinsp;cells in the dCA1 area of the experimental group, corroborating hippocampal engagement during navigation in VSL task (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo investigate whether MK-801 affects dCA1 neuronal activity related to the VSL task, we first administered tamoxifen to FosTRAP mice, followed by VSL task performance 30 minutes later to mark hippocampal c-Fos\u0026thinsp;+\u0026thinsp;cells with red fluorescence. After three days, mice were injected with either MK-801 or saline, and hippocampal brain tissue was harvested 30 minutes later for green fluorescent staining of c-Fos\u0026thinsp;+\u0026thinsp;cells (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD). In mice injected with MK-801, some neurons displayed green and red fluorescence, appearing yellow after merged (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eE). In contrast, in mice injected with saline, no dCA1 neurons were marked with green fluorescence (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eF). This consequence indicated a direct impact of MK-801 on dCA1 neurons associated with the VSL task.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003eEffect of MK-801 on Calcium activity of dCA1 neurons during VSL task\u003c/h2\u003e \u003cp\u003eTo characterize the activity pattern of dCA1 neurons when mice perform the VSL task, we conducted craniotomy and microinjected rAAV-CaMKII-GCaMP6s virus into the hippocampus dCA1. Three weeks later, neuronal calcium activity was detected via in vivo fluorescent microscopy, enabling observation of the real-time changes in neuronal activity during the task. (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA). Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB displays an example of calcium imaging consequence in the hippocampal dCA1 area during the VSL task. Using the Python-based suite2p toolkit, we identified and analyzed the calcium activity signals of individual neurons (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB and C). Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD further illustrates representative calcium activity of dCA1 neurons throughout the whole VSL task. As noted, MK-801-treated mice completed more trials but spent less time in the target area, showing intensified calcium signals. Using a threshold of mean plus standard deviation, we identified calcium transient peaks and observed significant increases in their frequency, amplitude, and half-width in MK-801-treated mice (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eE-G).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe correlation of neuronal population activity can help us better understand neural networks. Figure\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eH illustrates the representative result of correlation coefficients between the calcium activity signals of any two neurons in the hippocampal dCA1 area of the same mouse. Heatmap results show a significant decrease in neuronal population correlation in the MK-801 group. The average cumulative distribution curve of these correlation coefficients derived from six mice (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eI) indicated a significant reduction in the correlation of neuronal calcium activities in MK-801-treated mice. These results suggested that the disrupted neurons' activity and connectivity may account for spatial cognitive deficits in SZ mice.\u003c/p\u003e \u003cp\u003eFollowing analysis of spontaneous neuronal activity, we examined task-related spatial encoding. We calculated the place fields which reflect the spatial response range of neurons (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eJ). The place field width was significantly larger in MK-801-treated mice than in control (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eK), suggesting reduced spatial specificity of dCA1 neurons. MK-801 impaired the spatial encoding precision of dCA1 neurons, diminishing the mice's ability to integrate spatial information.\u003c/p\u003e \u003cp\u003eWe also analyzed the population calcium activity pre- and post-reward (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eL). Neurons were classified as reward-excited (23% of cells; increased post-reward activity), reward-inhibited (32%; decreased activity), or reward-neutral (45%; unchanged). By comparing the probability distribution of the Reward Preference Index [RPI = (post-reward - pre-reward) / (post-reward\u0026thinsp;+\u0026thinsp;pre-reward)] between these two groups of neurons (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eM). more neurons in the MK-801 group showed no significant changes in activity pre and post the reward. MK-801 administration shifted RPI distributions toward neutrality, concurrently reducing proportions of both reward-excited (15% vs. 23% in controls; p\u0026thinsp;\u0026lt;\u0026thinsp;0.01) and reward-inhibited neurons (16% vs. 32%; p\u0026thinsp;\u0026lt;\u0026thinsp;0.05; Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eN), indicating disrupted integration of spatial and reward information.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003eARI Reverses MK-801-Induced Neuronal and Spatial Cognitive Deficits\u003c/h2\u003e \u003cp\u003eTo assess ARI\u0026rsquo;s therapeutic potential, mice received MK-801 or saline, followed 30 min later by ARI or saline. Behavioral testing commenced 30 min post-second injection. The results showed no difference in behavioral performance between the ARI\u0026thinsp;+\u0026thinsp;Saline group and the Saline\u0026thinsp;+\u0026thinsp;Saline group (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB-D). As described previously, MK-801\u0026thinsp;+\u0026thinsp;Saline group mice compared to the Saline\u0026thinsp;+\u0026thinsp;Saline group exhibited increased running distance and speed, with a decrease in success rate (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB-D). However, the running distance and speed for mice in the MK-801\u0026thinsp;+\u0026thinsp;ARI group were reduced compared to the MK-801\u0026thinsp;+\u0026thinsp;Saline group (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB-C) and the reward rates increased (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eD).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIntraperitoneal injection of Saline followed by ARI had little impact on the frequency, amplitude, and half-width of neuronal calcium transients. However, ARI significantly reduced the abnormal increases in these parameters caused by MK-801 injection (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eE-G). ARI also partially restored the correlation between calcium activity signals in neurons of MK-801 treated mice (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eH). Furthermore, ARI reduced the width of the place fields in the dCA1 neurons of MK-801treated mice (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eI), increased the proportion of reward-preferred neurons, and enhanced neuronal reward preference (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eJ). ARI can correct abnormalities in excitatory activity of dCA1 neurons induced by MK-801 injection, enhancing the neurons' ability to encode spatial positioning and reward information, thereby alleviating spatial cognitive impairments.\u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this study, we investigated the relationship between spatial cognitive deficits and hippocampal hyperexcitability in a schizophrenia-relevant model using MK-801-treated mice. Our multimodal approach combined the virtual spatial location (VSL) task with in vivo calcium imaging to characterize dorsolateral CA1 (dCA1) neural circuit dysfunction and evaluate the therapeutic efficacy of aripiprazole (ARI). Behavioral consequences revealed MK-801-induced hyperlocomotion and impaired spatial navigation, similar to the behaviors observed in patients with SZ. Cellular-level analysis demonstrated pathological hyperactivity in dCA1 neurons, manifesting as dysregulated calcium signaling dynamics (increased frequency, amplitude, and half-peak width) accompanied by desynchronized network activity, which diminished the accuracy of spatial and reward information encoding. Furthermore, ARI treatment effectively corrected these abnormalities in dCA1 neuron activity, reducing spontaneous movement and alleviating spatial cognitive impairments. These findings enhance our understanding of the neural mechanisms underlying spatial cognitive impairments in SZ and provide experimental evidence supporting clinical treatment.\u003c/p\u003e \u003cp\u003ePrevious studies have shown that acute low-dose MK-801 injection leads to increased spontaneous movement and cognitive impairments in mice during Morris water maze and Y-maze tasks \u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e, establishing links between NMDAR hypofunction and SZ-related spatial cognitive impairment \u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e. However, few experiments simultaneously recorded neuronal activity and assessed spatial cognition performance. We developed a head-fixed mouse VSL task where mice identify reward-related virtual spatial areas and stay in them to get water rewards. To address this gap, we monitored the excitatory calcium activity of hippocampal dCA1 neurons using in vivo calcium imaging. Our results showed that mice treated with acute MK-801 displayed increased spontaneous movement and impaired spatial recognition, confirming the task's effectiveness in detecting spatial cognitive impairments and related neuronal activity abnormalities in SZ.\u003c/p\u003e \u003cp\u003eThe hippocampus serves as a critical neural substrate for learning and memory \u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e. The dCA1 region, receiving inputs from the entorhinal cortex and CA3 \u003csup\u003e[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e, functions as a principal hippocampal hub for contextual information integration. Our brain slice immunofluorescence analyses revealed increased c-Fos expression in post-task dCA1 neurons, with MK-801 administration reactivating neurons originally expressing c-Fos during VSL task performance. This demonstrates that spatial cognition-related neural activity can be directly modulated by NMDAR blockade. Complementing previous observations of epileptiform spike-wave discharges and diminished inter-hippocampal synchrony in dCA1 neurons of neonatal hippocampal lesion SZ models \u003csup\u003e[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e. Similarly, our results showed increased frequency, amplitude, and half-peak width of calcium transients, and a decrease in the synchrony across neurons. Thus, MK-801 induced abnormal excitatory activity in dCA1 neurons, while reduced the coordination among neurons. These findings indicate that NMDAR hypofunction induces both hyperexcitability and impaired interneuronal coordination in dCA1 circuits. Collectively, disrupted neuronal communication in SZ may underlie deficits in spatial information encoding and memory consolidation processes.\u003c/p\u003e \u003cp\u003eThe hippocampal dCA1 region contains place cells critical for spatial cognition, encoding discrete spatial locations through well-defined place fields \u003csup\u003e[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e. Studies involving olfactory-based spatial navigation tasks revealed that mice with narrower place fields in the dCA1 region exhibited higher precision in spatial encoding, which correlated with an improvement of performance in goal-directed spatial tasks \u003csup\u003e[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e. Our results showed that dCA1 neurons in control mice were selectively activated at specific spatial locations, forming clear place fields. In contrast, MK-801-treated mice exhibited broader place fields, indicating reduced spatial encoding precision. Impaired dCA1 place cells may hinder the hippocampal network's ability to differentiate spatial contexts. This impairment may be caused by damage to synaptic plasticity or reduced coordination among neurons, both of which are critical for encoding and retrieving spatial memories \u003csup\u003e[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]\u003c/sup\u003e. This question remains to be analyzed in future studies whether this impairment is specifically due to synaptic abnormalities, network dysfunction, or a combination of both.\u003c/p\u003e \u003cp\u003eDue to the increased speed in SZ model mice, the enlargement of place fields in place cells may potentially be attributed to the increase in speed. Previous study has suggested that a small subset of place cells exhibit speed-modulated firing rates \u003csup\u003e[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]\u003c/sup\u003e. Since hyperactivity and spatial cognitive impairment are comorbid in SZ patients and interlinked in animal models, there is currently no effective method to validate whether the increase in speed and the widening of place fields are separate.\u003c/p\u003e \u003cp\u003ePrevious studies also suggest hippocampal dCA1 area, might process and store reward information \u003csup\u003e[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/sup\u003e. These neurons may show increased activity during reward-related stimuli or exploring reward-associated spaces, helping animals remember reward-relevant details like location or context \u003csup\u003e[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e. In spatial navigation task, the intensity and proportion of hippocampal dCA1 reward-responsive neurons correlated with successful task completion, reflecting robust reward-related information encoding \u003csup\u003e[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/sup\u003e. In this study, we also found enhanced or diminished calcium transient activity in normal dCA1 neurons upon entering reward zones, indicating their involvement in processing reward information. In mice treated with MK-801, our results indicated a reduced proportion of reward-associated neurons within the hippocampus, alongside attenuated responses to reward stimuli. These findings suggest a compromised capacity for encoding reward information in the hippocampal region. Consequently, this impairment disrupts the effective integration of spatial and reward information, which is crucial for accurately navigating and performing in VSL task. This deficit in integrating key cognitive components highlights the critical role of hippocampal functionality in complex behavioral tasks reliant on both spatial and reward cues.\u003c/p\u003e \u003cp\u003eAripiprazole (ARI), an atypical antipsychotic, acts as a partial agonist at dopamine D2 receptors and 5-HT1A receptors, and as an antagonist at 5-HT2A receptors \u003csup\u003e[\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]\u003c/sup\u003e. Excessive dopamine activity in the mesolimbic system is closely associated with positive symptoms. Conversely, reduced dopamine activity in the prefrontal cortex may contribute to negative symptoms \u003csup\u003e[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/sup\u003e. While ARI effectively treats the positive and negative symptoms of SZ, its impact on cognitive symptoms remains unclear. Previous studies indicated that ARI could alleviate spatial cognitive impairments in preclinical SZ models during water maze \u003csup\u003e[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/sup\u003e. Our study found that ARI reduced the frequency, amplitude, and half-peak width of calcium transients in the dCA1 neurons of MK-801-treated mice, increased the synchronization of neuronal activity, narrowed place fields, and improved the proportion and response strength of reward-reactive neurons. ARI treatment also mitigated MK-801-induced hyper locomotion and improved the accuracy of spatial recognition in VSL tasks, suggesting that ARI might alleviated cognitive disorders by correcting abnormal neuronal activities in dCA1.\u003c/p\u003e \u003cp\u003eIn conclusion, our study revealed that MK-801-induced spatial cognition impairments in mice are associated with reduced neuronal synchronization and encoding accuracy of spatial and reward information in hippocampal dCA1 neurons. Moreover, ARI showed potential therapeutic effects in restoring neuronal function and improving spatial cognition. These findings advance our understanding of SZ pathophysiology and underscore hippocampal circuit modulation as a strategic target for cognitive therapeutics.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eAuthor Contributions\u003c/h2\u003e \u003cp\u003eLing Qin and Pingting Yang conceptualized, designed and supervised the studies. Zijie Li and Xueru Wang set up the experiment equipments and analyzed the results. Xueying Yang, Xuejiao Wang and Huangyu Wang performed the experiments. Zijie Li, Xueying Yang and Ling Qin drafted the paper. All authors have read and approved the paper.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eThe study was funded by the Chinese National Key Technology R\u0026amp;D Program (2021YFC2501303 to PTY), the Joint Funds of the National Natural Science Foundation of China (U22A20309 to PTY), the Department of Science and Technology of Liaoning Province (2021JH1/10400049 to LQ), the 'Xingliao Talent Plan' of Liaoning Province (XLYC2002094 to LQ), National Natural Science Foundation of China (Youth Fund, No.82301533 to XJW).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eO'Keefe J, Dostrovsky J. The hippocampus as a spatial map. Preliminary evidence from unit activity in the freely-moving rat. Brain Res. 1971. 34(1): 171\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBatinic B. Cognitive Models of Positive and Negative Symptoms of Schizophrenia and Implications for Treatment. 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Clin Ther. 2004. 26(5): 649\u0026ndash;66.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Schizophrenia, Spatial cognition, Hippocampal abnormalities, NMDAR hypofunction, Calcium imaging, Aripiprazole","lastPublishedDoi":"10.21203/rs.3.rs-6252679/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6252679/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSpatial cognitive-behavioral deficits represent core clinical symptoms of schizophrenia (SZ), yet their neurophysiological mechanisms and effective treatment strategies remain unclear. Previous research has indicated a reduction in hippocampal volume and weakened intercellular connectivity in SZ patients, but the causal link between these hippocampal abnormalities and spatial cognitive impairments is poorly defined. To investigate this relationship, we used a virtual spatial location (VSL) task and in vivo calcium imaging in MK-801-treated mice. Furthermore we evaluated the therapeutic effects of aripiprazole (ARI). Behavioral analyses revealed that MK-801-treated mice exhibited hyperactivity (increased locomotor distance and speed) and pronounced spatial working memory deficits. Calcium imaging in the hippocampal dorsal CA1 (dCA1) region demonstrated aberrant neuronal hyperactivity, characterized by elevated calcium signal frequency, amplitude, and half-width duration, alongside impaired neural synchronization and diminished encoding precision for spatial-reward associations. ARI treatment significantly mitigated these behavioral and neuronal abnormalities. These findings establish a direct correlation between MK-801-induced hippocampal excitatory dysregulation and spatial cognitive deficits, while highlighting ARI\u0026rsquo;s therapeutic potential in mitigating schizophrenia-related spatial cognitive-behavioral impairments.\u003c/p\u003e","manuscriptTitle":"Correlation between abnormal hippocampal neural activities and spatial cognitive impairments in the model mice of schizophrenia and therapeutic effects of aripiprazole","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-04-16 08:56:41","doi":"10.21203/rs.3.rs-6252679/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"18470c6c-3105-440b-85f5-c1d3bc1c0db2","owner":[],"postedDate":"April 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":46286798,"name":"Biological sciences/Neuroscience/Learning and memory/Hippocampus"},{"id":46286799,"name":"Biological sciences/Neuroscience"}],"tags":[],"updatedAt":"2025-06-27T09:13:02+00:00","versionOfRecord":[],"versionCreatedAt":"2025-04-16 08:56:41","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6252679","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6252679","identity":"rs-6252679","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}