Modulating Delay Discounting in ADHD: A Multi-Sessional tDCS Intervention

Modulating Delay Discounting in ADHD: A Multi-Sessional tDCS Intervention | 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 Modulating Delay Discounting in ADHD: A Multi-Sessional tDCS Intervention Zeynab Agahi, Vahid Nejati This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6330387/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 13 You are reading this latest preprint version Abstract Background Individuals with Attention-Deficit/Hyperactivity Disorder (ADHD) often exhibit delay discounting, a preference for smaller immediate rewards over larger delayed rewards, which is linked to executive function deficits and impulsive decision-making. The right dorsolateral prefrontal cortex (rdlPFC) plays a crucial role in cognitive control and impulse regulation, making it a potential target for non-invasive brain stimulation interventions. Objective This study aimed to investigate the effects of anodal transcranial direct current stimulation (tDCS) over the rdlPFC on delay discounting in children with ADHD. We hypothesized that active tDCS would enhance cognitive control, reducing impulsivity and increasing the selection of delayed rewards. Methods Using a single-blind, randomized parallel-group design, twenty-one children with ADHD (aged 7–12 years) were randomly assigned to either the active tDCS or sham stimulation group. The intervention consisted of 10 sessions of 1 mA anodal tDCS applied to the rdlPFC over three weeks. Participants completed a Chocolate Delay Discounting Task (CDDT) at three time points: pre-intervention, post-intervention, and two-month follow-up. A mixed ANOVA was conducted to examine the effects of tDCS on delay discounting rates (K index) across conditions. Results The interaction between group and time was significant for the total K index (F = 4.3, p < 0.02, ηp² = 0.18) and the 20-chocolate K index (F = 3.2, p < 0.05, ηp² = 0.14), indicating that anodal tDCS increased the likelihood of selecting delayed rewards compared to the sham condition. However, the main effects of group and time were not significant. No significant differences were observed for the 10-, 5-, and 2-chocolate K indices. Conclusion These findings suggest that anodal tDCS over the rdlPFC reduce delay discounting in children with ADHD, particularly in high-reward scenarios. Given the long-term follow-up results, tDCS could serve as a promising intervention for addressing impulsivity-related deficits in ADHD. Biological sciences/Neuroscience Biological sciences/Psychology ADHD delay discounting cognitive control transcranial direct current stimulation (tDCS) dorsolateral prefrontal cortex (dlPFC) impulsivity Figures Figure 1 Figure 2 Figure 3 Introduction Individuals with ADHD often struggle with future-oriented perception and exhibit deficits in reward processing. A well-documented challenge is their preference for smaller, immediate rewards over larger, delayed ones, reflecting a heightened discounting of delayed rewards. This tendency is attributed to altered sensitivity to reinforcement 1 , 2 . According to the delay aversion theory, individuals with ADHD have difficulties perceiving time accurately, leading to reduced tolerance for delays. This intolerance is driven by motivational factors and impaired time perception, contributing to maladaptive decision-making. Delay aversion in ADHD is associated with executive function deficits and the negative emotional responses triggered by waiting, making it particularly difficult for individuals to manage 3 . Research consistently demonstrates that individuals with ADHD exhibit a strong preference for smaller, immediate rewards over larger, delayed ones 4 – 9 . This behavior is often characterized as impulsivity, as individuals fail to consider the long-term consequences of their choices. Moreover, the severity of hyperactive-impulsive symptoms in ADHD is directly correlated with the rate of delay discounting 10 . In addition to impulsive choice patterns, individuals with ADHD frequently engage in risky financial behaviors, such as accumulating debt and making late credit card payments. These behaviors reflect a broader pattern of impulsive decision-making that is closely linked to ADHD symptoms and delay discounting tendencies 11 . Altered time perception in individuals with ADHD significantly impacts their tolerance for delays and impairs higher cognitive functions, including decision-making. Consequently, risky decision-making is a common challenge among individuals with ADHD 12 . Several brain regions are implicated in delay discounting, particularly those involved in cognitive control, emotional processing, and reward evaluation 13 , 14 . Functional magnetic resonance imaging (fMRI) studies in healthy adults indicate that immediate rewards activate the ventral striatum, medial orbitofrontal cortex (mOFC), medial prefrontal cortex (mPFC), and posterior cingulate cortex (PCC). In contrast, brain regions associated with cognitive control and delayed rewards, such as the dorsolateral prefrontal cortex (dlPFC), ventrolateral prefrontal cortex (vlPFC), and lateral orbitofrontal cortex (lOFC), are activated when individuals engage in deliberative decision-making 15 . Additionally, gray matter volume in the dlPFC and inferior frontal cortex is inversely correlated with delay discounting rates 16 . Understanding how these brain regions contribute to reward delay processing enables the targeted modulation of specific cortical areas through non-invasive brain stimulation (NIBS) techniques, such as transcranial electrical stimulation (tES) and transcranial magnetic stimulation (TMS). These methods allow researchers to evaluate whether stimulating certain brain regions can effectively improve delay discounting 17 . Transcranial direct current stimulation (tDCS), a form of tES, applies a low electrical current to the scalp, influencing neuronal excitability. Depending on the polarity of the stimulation, tDCS can either enhance or reduce the excitability of cortical targets, modulating cognitive functions at a macroscopic level 18 . Beyond its immediate effects, tDCS also promotes synaptic plasticity in glutamatergic pathways, contributing to its potential long-term impact 19 . tDCS has been used to alleviate symptoms and enhance cognitive performance in psychiatric disorders 20 . In individuals with ADHD, anodal tDCS over the left dorsolateral prefrontal cortex (lDLPFC) has been shown to improve clinical symptoms and cognitive functions, including memory consolidation 21 , inhibitory control 22 , selective attention 23 , working memory and interference control 24 , and sustained attention 25 . Studies on children with ADHD have also demonstrated the beneficial effects of tDCS on cognitive functions 26 . A meta-analysis further revealed that the left and right dlPFC are the most commonly targeted regions for ADHD treatment, with anodal tDCS being the most frequently applied protocol 26 . Executive function deficits are a core component of ADHD pathophysiology 27 and are linked to reduced dlPFC activation alongside increased activity in certain subcortical regions 28 . Given that the severity of hyperactive/impulsive symptoms in ADHD is positively correlated with the rate of delay discounting 10 , and that the right dorsolateral prefrontal cortex (rdlPFC) plays a crucial role in modulating impulsive behavior, decision-making, and self-control, targeting this region through tDCS presents a promising therapeutic avenue. The rdlPFC is particularly vital for inhibitory control and risk assessment, making its modulation relevant not only for ADHD but also for other impulsivity-related disorders, such as addiction and obesity 29 – 33 . Therefore, we targeted the rdlPFC in this study. Our hypothesis highlights the central role of the rdlPFC in regulating delay discounting, proposing that alterations in this brain region contribute to ADHD symptoms. While most studies have used single-session protocols with online evaluations of delay discounting, few have investigated the long-term effects of interventions targeting the dlPFC. To address this gap, our study implemented a multi-session intervention to assess its impact on delay discounting in children with ADHD. Additionally, we aimed to evaluate the durability of these effects through follow-up assessments post-intervention. By adopting a multi-session approach, our research seeks to provide deeper insights into whether sustained modulation of the dlPFC can lead to long-term improvements in delay discounting and impulsive decision-making in ADHD. Materials and methods Participants. Twenty-five children with ADHD, aged 7–12 years (mean age = 9 ± 1.5 years; 14 boys, 11 girls), participated in the study. Table 1 presents the demographic characteristics of the participants. ADHD diagnoses were based on the criteria outlined in the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition 34 and were confirmed by a professional psychiatrist or clinical psychologist at mother and Childe clinic of Shahid Beheshti university. All participants were medication-free both before and during the tDCS sessions. None had a current or past history of traumatic head injury, seizures, autism, conduct disorder, or any other severe mental or neurological disorder, as determined through a clinical interview conducted by a psychiatrist or clinical psychologist. Participants had normal IQ scores, with an exclusion criterion of IQ below 80 or above 130. The study procedures adhered to the ethical standards of the Declaration of Helsinki (1975, revised in 2013) and were approved by the local ethics committee at Shahid Beheshti University. The task was presented on a laptop with a 15.600 screen and the viewing distance from the monitor was approximately 50 cm. this task had an initial stage to make participants familiar with the task. Chocolate delay discounting task (CDDT) The delay discounting task requires participants to choose between a small, immediate reward and a larger reward that is delayed. During task performance, both the length of the delay and the size of the postponed reward increase. The individual’s turning point in decision-making—where they shift preference between immediate smaller rewards and delayed larger rewards—makes this task a valuable tool for assessing. Instead of monetary choices, as chocolate serves as a well-suited primary reward for children 35 . The task was presented on a laptop with a 15.6-inch screen, and the viewing distance reward processing. In this study, we used chocolate images (Fig. 1). Figure was approximately 50 cm. To ensure participants understood the task, an initial familiarization stage was included. This task has previously been used with children with ADHD as an intervention-sensitive measure 24 . The immediate reward consisted of one chocolate bar, while the delayed rewards comprised two, five, ten, and twenty chocolate bars, available after 1 day, 2 days, 3 days, 5 days, 1 week, and 1 month, respectively. The main variable of this task is the rate of discounting (K), calculated using the function: Vi = Ai / (1 + Ki × Di), where Vi represents the present value of the reward, Ai is the delayed reward, Di is the delay, and Ki is the discount rate 36 . The discounting rates (K values) were computed separately for each condition, and the mean discount rate (Kmean) was derived by averaging them. Task completion took approximately 5 minutes per participant. tDCS protocol The ActivaDose transcranial stimulator (ActivaTek Inc., USA) was used for brain stimulation. A direct current of 1 mA was applied through saline-soaked sponge electrodes measuring 24 cm² (4 × 6 cm) for 20 minutes, with a 15-second ramp-up and 15-second ramp-down period. The anodal electrode was positioned over the right dorsolateral prefrontal cortex (rdlPFC; F4) according to the 10–20 EEG international system and cathodal electrode over the left arm (Fig. 2), and stimulation was administered over 10 sessions. At the end of each session, participants were asked about any side effects experienced during stimulation using a standardized side effect survey. The experimenter responsible for administering tDCS was not blinded to the study hypotheses or tDCS condition (active vs. sham). For sham stimulation, the electrical current was ramped up for 30 seconds to produce the same initial sensation as in the active condition, after which it was turned off without the participants’ awareness 37 . Procedure. After obtaining written informed consent from the parents of children with ADHD, participants were randomly assigned to two groups: the tDCS group and the control group. Zeinab Agahie the first author allocated participant in tDCS group or Sham. Assessments were conducted in three separate sessions: pre-intervention (immediately before the first experimental session), post-intervention (immediately after the final session), and a 2-month follow-up assessment. Study design. Participants in the electrical stimulation groups were blinded to their stimulation condition (i.e., active vs. sham). Stimulation sessions were conducted in a quiet room, three times per week on non-consecutive days, to prevent carry-over effects. All computerized tasks, including stimuli presentation, were controlled by a laptop with a 15.6-inch screen, positioned at a viewing distance of approximately 50 cm. Before the experiment, participants received instructions on the CDD task, with detailed written instructions displayed on the screen before the task began. We used Mix Anova to analyze data. Statistical analysis The data collected in this study analyzed using SPSS version 21. The primary outcome measure, the delay discounting rate, quantified using the k-index. To assess the effects of tDCS on delay discounting, a mixed-design ANOVA conducted. The independent variable was group (active tDCS vs. sham), and the within-subjects factor were time (baseline, post-intervention, and follow-up) The level of significance for all statistical tests set at p < 0.05. Results All participants tolerated the stimulation well, with no significant side effects reported during or after the sessions, confirming the safety and tolerability of the procedure. No adverse events or unintended effects were observed or reported by participants or their parents during the course of the study. No significant group differences were found in demographic characteristics (see Table 1). The mean and standard deviation of the intervention (tDCS) and sham conditions for each K index—2 chocolates, 5 chocolates, 10 chocolates, 20 chocolates, and the total K index—are presented in Table 2. The results of the ANOVA revealed a significant interaction between group and time for the total K index (F = 4.3, p < 0.02, ηp² = 0.18). However, neither the main effect of group nor the main effect of time showed significant differences (see Table 3). A similar pattern was observed for the 20-chocolate K index, where the interaction between group and time was significant (F = 3.2, p < 0.05, ηp² = 0.14), but the main effects of group and time were not significant. For the 10-chocolate K index, no significant differences were found in the interaction between group and time, nor in the main effects of group or time. Likewise, no significant differences were observed for the 5-chocolate K index or the 2-chocolate K index. Discussion The results of our study suggest that anodal tDCS over the right dorsolateral prefrontal cortex (rdlPFC) increases the likelihood of choosing delayed rewards in children with ADHD compared to sham stimulation. In cognitive theories of ADHD, the dlPFC, a critical region for executive functions, is known to be hypoactive in individuals with ADHD, leading to functional deficits 38 , 39 . Our findings support prior research demonstrating the essential role of the dlPFC in executive functions and cognitive control 25 , 40 – 43 . Additionally, our results align with previous studies showing that anodal tDCS over the right dlPFC significantly enhances cognitive control 44 , 45 and increases participants' preference for larger, delayed rewards compared to sham stimulation 46 . Neural Mechanisms of Delay Discounting. Delay discounting involves two key neural systems, as demonstrated by functional magnetic resonance imaging (fMRI) studies in healthy adults. The immediate reward system, responsible for reward processing, includes the ventral striatum, medial orbitofrontal cortex (mOFC), medial prefrontal cortex (mPFC), and posterior cingulate cortex (PCC). In contrast, the delayed reward system, associated with cognitive control, engages the dorsolateral prefrontal cortex (dlPFC), ventrolateral prefrontal cortex (vlPFC), and lateral orbitofrontal cortex (lOFC) 15 . In a previous study, we targeted the reward-processing system using anodal right ventromedial prefrontal cortex (vmPFC) stimulation and cathodal left dlPFC stimulation 42 . In contrast, the current study focused on the cognitive control system by stimulating the rdlPFC. Given that the dlPFC plays a central role in cognitive control, our findings suggest that its hypoactivity is linked to an increased tendency for delay discounting in children with ADHD. These results align with neuroimaging studies demonstrating that reduced dlPFC activation correlates with impaired executive function and increased impulsivity 38 , 39 . Moreover, previous studies have shown that the severity of hyperactive/impulsive symptoms in ADHD is positively correlated with delay discounting rates 10 . The rdlPFC is crucial for impulse control, decision-making, and self-regulation. Its role in inhibitory control and risk assessment suggests that modulating this region via tDCS could provide a therapeutic avenue for addressing impulsivity-related disorders, including ADHD, addiction, and obesity 30 – 33 , 47 . Our findings support this perspective, highlighting that anodal tDCS over the rdlPFC can effectively modulate delay discounting, potentially offering therapeutic benefits for impulsivity and decision-making deficits. Long-Term Effects and Neuroplasticity. A key feature of this study was the inclusion of a follow-up session to evaluate the long-term effects of tDCS. While most studies focus on single-session or short-term interventions, assessing executive function (EF) during, before, or immediately after stimulation 25 , 40 , 42 , 43 , our study uniquely examined delay discounting two months post-stimulation. This approach allowed us to assess the lasting impact of the intervention beyond the stimulation period. Additionally, this study focused on children, considering that childhood and adolescence are critical periods of neurodevelopment and heightened neuroplasticity. Early interventions can leverage neuroplasticity to establish new pathways that compensate for deficits. The earlier the intervention occurs, the greater its potential impact due to the brain's increased plasticity during these formative years 48 . Limitations and Future Directions . Despite the promising findings of this study, several limitations should be acknowledged. One key limitation was the reduction in sample size after the follow-up sessions, which may have influenced the statistical power and reliability of the results. Future studies should aim to include a larger sample size to enhance the generalizability of the findings. Additionally, the researcher conducting tDCS was not blinded to the study conditions, which could introduce potential bias in the experimental procedure. Implementing a double-blind design in future research would improve methodological rigor and reduce potential experimenter effects. Another important consideration is the duration and frequency of the stimulation protocol. While our study applied ten tDCS sessions, future studies should explore whether increasing the number of sessions leads to more pronounced and lasting effects. Moreover, the current study targeted the cognitive control system by stimulating the right dlPFC, whereas previous studies have also focused on the reward-processing system 42 . Future research should compare these two approaches or investigate the combined effects of stimulating both the cognitive control and reward-processing networks to determine the most effective intervention strategy for reducing delay discounting in individuals with ADHD. Finally, while this study focused on children, future research should examine whether similar effects can be observed in adolescents and adults with ADHD. Given that brain plasticity changes with age, understanding how age-related differences influence the effectiveness of tDCS on delay discounting would provide valuable insights into optimizing intervention strategies. By addressing these limitations and expanding the scope of research, future studies can further refine the application of non-invasive brain stimulation as a potential therapeutic tool for improving decision-making and impulse control in individuals with ADHD. Conclusion Overall, tDCS represents a promising tool for modulating delay discounting through targeted stimulation of the dlPFC. By enhancing cognitive control and reducing impulsivity, tDCS has the potential to serve as an effective intervention for individuals with difficulty in time perception and impulse control. However, further research—including comparative studies with larger sample sizes—is necessary to fully understand its effects across different populations and contexts. Declarations Competing interests The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. 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Descriptive Statistics (Mean, Standard Deviation) of chocolate delay discounting task(CDDT) Situation tDCS M(SD) Sham M(SD) Pre test Post test Follow up Pre test Post test Follow up 2 chocolate K 1.03(1.28) .36(.38) .60(.44) 1.03(1.1) .63(.30) .59(.34) 5 chocolate K 1.8(1.6) 1.2(1.2) 1(1.2) 2.08(1.6) 1.9(1.6) 1.9(1.7) 10 chocolate K 4.4(4.1) 3.5(3.8) 2.1(2.7) 5.1(3.7) 4.4(3.1) 6.1(3.5) 20 chocolate K 5.9(7.2) 4.2(5.6) 2.03(2.01) 4.5(7.2) 3.8(5.4) 8.3(8.7) Total K index 3.3(2.06) 2.3(2.4) 1.4(1.06) 3.2(2.3) 2.7(2.1) 4.2(2.9) Abbreviation: tDCS: transcranial direct current stimulation, M: mean, SD: standard deviation, CDD: chocolate delay discounting task Table 3. Results of the Repeated Measures ANOVAs for Effects of tDCS Conditions (Sham/Anodal rDLPFC) Measures Time Effect Group Effect Time * Group df F p ηp2 df F p ηp2 df F p ηp2 2 chocolate K 2 2.86 .06 .13 1 .17 .6 .009 2 .23 .79 .01 5 chocolate K 2 .78 .4 ..04 1 1.7 .20 .08 2 .315 .7 .01 10 chocolate K 2 .312 .73 .01 1 3.3 .08 .14 2 1.6 .2 .08 20 chocolate K 2 .34 .7 .01 1 .53 .47 .02 2 3.2 .05 .14 Total K index 2 .95 .39 .04 1 1.7 .2 .08 2 4.3 .02 .18 Additional Declarations No competing interests reported. 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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-6330387","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":453755147,"identity":"d741dd33-5126-4ef4-ab05-bf4e0fb18266","order_by":0,"name":"Zeynab Agahi","email":"","orcid":"","institution":"Shahid Beheshti University","correspondingAuthor":false,"prefix":"","firstName":"Zeynab","middleName":"","lastName":"Agahi","suffix":""},{"id":453755150,"identity":"06e4e25f-0f59-4ae9-bcef-8da402ccc821","order_by":1,"name":"Vahid Nejati","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAv0lEQVRIiWNgGAWjYHCCBAYGAxsGAwhHgkgtBwzSSNPCwHCA4TBMCxHAnL3h4ecPBeftzSUSGD/8YLDIJ6jFsudAssQBg9uJO2ckMEv2MEhYNhDSYnAjIQGkJQHIYJAG+oWwAw3uP0j+ccDgnD1QC/Nv4rTcYEgD2nKAccONBDYibTmTkGZxxiA5cWfPwzbLHgNitBw/k3yj4o+dvTl78uEbPyrqiAlsngQog7GBgcjYYT9AlLJRMApGwSgYwQAAey86fu04yKYAAAAASUVORK5CYII=","orcid":"","institution":"Shahid Beheshti University","correspondingAuthor":true,"prefix":"","firstName":"Vahid","middleName":"","lastName":"Nejati","suffix":""}],"badges":[],"createdAt":"2025-03-28 18:53:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6330387/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6330387/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":82582213,"identity":"2f9bd862-b9a0-4abd-ba9d-36a269900597","added_by":"auto","created_at":"2025-05-13 06:43:02","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":33701,"visible":true,"origin":"","legend":"\u003cp\u003eshown graphical picture of chocolate bar, number of chocolate and number of delayed days\u003c/p\u003e","description":"","filename":"figure1.png","url":"https://assets-eu.researchsquare.com/files/rs-6330387/v1/6c418184cda2a0a3c1b992b3.png"},{"id":82583626,"identity":"9bbb3749-0d29-420d-a1f2-459bdb3500cb","added_by":"auto","created_at":"2025-05-13 06:51:02","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":141118,"visible":true,"origin":"","legend":"\u003cp\u003ecourse of study\u003c/p\u003e","description":"","filename":"figure2.png","url":"https://assets-eu.researchsquare.com/files/rs-6330387/v1/3fb97511cab15573953f8ab7.png"},{"id":82582214,"identity":"74013652-24ec-422f-b7d8-434bb89c3e70","added_by":"auto","created_at":"2025-05-13 06:43:02","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":18446,"visible":true,"origin":"","legend":"\u003cp\u003eShown are the effects of tDCS on different variables of the delay discounting task. Note. K = the index of delay discounting in different values. The horizontal bars are showing the means and the error bars the range of variables.\u003c/p\u003e","description":"","filename":"figure3.png","url":"https://assets-eu.researchsquare.com/files/rs-6330387/v1/b9d47542d0267ac135565dff.png"},{"id":82585190,"identity":"3b359839-6aa8-499c-8695-cbea532f3399","added_by":"auto","created_at":"2025-05-13 07:07:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1027249,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6330387/v1/002b45d3-eeef-4b2d-8b7a-b18f120d208d.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Modulating Delay Discounting in ADHD: A Multi-Sessional tDCS Intervention","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIndividuals with ADHD often struggle with future-oriented perception and exhibit deficits in reward processing. A well-documented challenge is their preference for smaller, immediate rewards over larger, delayed ones, reflecting a heightened discounting of delayed rewards. This tendency is attributed to altered sensitivity to reinforcement \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. According to the delay aversion theory, individuals with ADHD have difficulties perceiving time accurately, leading to reduced tolerance for delays. This intolerance is driven by motivational factors and impaired time perception, contributing to maladaptive decision-making. Delay aversion in ADHD is associated with executive function deficits and the negative emotional responses triggered by waiting, making it particularly difficult for individuals to manage \u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eResearch consistently demonstrates that individuals with ADHD exhibit a strong preference for smaller, immediate rewards over larger, delayed ones \u003csup\u003e\u003cspan additionalcitationids=\"CR5 CR6 CR7 CR8\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. This behavior is often characterized as impulsivity, as individuals fail to consider the long-term consequences of their choices. Moreover, the severity of hyperactive-impulsive symptoms in ADHD is directly correlated with the rate of delay discounting \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. In addition to impulsive choice patterns, individuals with ADHD frequently engage in risky financial behaviors, such as accumulating debt and making late credit card payments. These behaviors reflect a broader pattern of impulsive decision-making that is closely linked to ADHD symptoms and delay discounting tendencies \u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAltered time perception in individuals with ADHD significantly impacts their tolerance for delays and impairs higher cognitive functions, including decision-making. Consequently, risky decision-making is a common challenge among individuals with ADHD \u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Several brain regions are implicated in delay discounting, particularly those involved in cognitive control, emotional processing, and reward evaluation \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Functional magnetic resonance imaging (fMRI) studies in healthy adults indicate that immediate rewards activate the ventral striatum, medial orbitofrontal cortex (mOFC), medial prefrontal cortex (mPFC), and posterior cingulate cortex (PCC). In contrast, brain regions associated with cognitive control and delayed rewards, such as the dorsolateral prefrontal cortex (dlPFC), ventrolateral prefrontal cortex (vlPFC), and lateral orbitofrontal cortex (lOFC), are activated when individuals engage in deliberative decision-making \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Additionally, gray matter volume in the dlPFC and inferior frontal cortex is inversely correlated with delay discounting rates \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eUnderstanding how these brain regions contribute to reward delay processing enables the targeted modulation of specific cortical areas through non-invasive brain stimulation (NIBS) techniques, such as transcranial electrical stimulation (tES) and transcranial magnetic stimulation (TMS). These methods allow researchers to evaluate whether stimulating certain brain regions can effectively improve delay discounting \u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Transcranial direct current stimulation (tDCS), a form of tES, applies a low electrical current to the scalp, influencing neuronal excitability. Depending on the polarity of the stimulation, tDCS can either enhance or reduce the excitability of cortical targets, modulating cognitive functions at a macroscopic level\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Beyond its immediate effects, tDCS also promotes synaptic plasticity in glutamatergic pathways, contributing to its potential long-term impact \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003etDCS has been used to alleviate symptoms and enhance cognitive performance in psychiatric disorders \u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. In individuals with ADHD, anodal tDCS over the left dorsolateral prefrontal cortex (lDLPFC) has been shown to improve clinical symptoms and cognitive functions, including memory consolidation \u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e, inhibitory control \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e, selective attention \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, working memory and interference control\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e, and sustained attention \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. Studies on children with ADHD have also demonstrated the beneficial effects of tDCS on cognitive functions \u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. A meta-analysis further revealed that the left and right dlPFC are the most commonly targeted regions for ADHD treatment, with anodal tDCS being the most frequently applied protocol \u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eExecutive function deficits are a core component of ADHD pathophysiology \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e and are linked to reduced dlPFC activation alongside increased activity in certain subcortical regions \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. Given that the severity of hyperactive/impulsive symptoms in ADHD is positively correlated with the rate of delay discounting \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e, and that the right dorsolateral prefrontal cortex (rdlPFC) plays a crucial role in modulating impulsive behavior, decision-making, and self-control, targeting this region through tDCS presents a promising therapeutic avenue. The rdlPFC is particularly vital for inhibitory control and risk assessment, making its modulation relevant not only for ADHD but also for other impulsivity-related disorders, such as addiction and obesity \u003csup\u003e\u003cspan additionalcitationids=\"CR30 CR31 CR32\" citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. Therefore, we targeted the rdlPFC in this study.\u003c/p\u003e \u003cp\u003eOur hypothesis highlights the central role of the rdlPFC in regulating delay discounting, proposing that alterations in this brain region contribute to ADHD symptoms. While most studies have used single-session protocols with online evaluations of delay discounting, few have investigated the long-term effects of interventions targeting the dlPFC. To address this gap, our study implemented a multi-session intervention to assess its impact on delay discounting in children with ADHD. Additionally, we aimed to evaluate the durability of these effects through follow-up assessments post-intervention. By adopting a multi-session approach, our research seeks to provide deeper insights into whether sustained modulation of the dlPFC can lead to long-term improvements in delay discounting and impulsive decision-making in ADHD.\u003c/p\u003e"},{"header":"Materials and methods","content":"\u003cp\u003e\u003cstrong\u003eParticipants.\u003c/strong\u003e Twenty-five children with ADHD, aged 7\u0026ndash;12 years (mean age\u0026thinsp;=\u0026thinsp;9\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5 years; 14 boys, 11 girls), participated in the study. Table 1 presents the demographic characteristics of the participants. ADHD diagnoses were based on the criteria outlined in the \u003cem\u003eDiagnostic and Statistical Manual of Mental Disorders, 5th Edition\u003c/em\u003e\u003csup\u003e\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e and were confirmed by a professional psychiatrist or clinical psychologist at mother and Childe clinic of Shahid Beheshti university. All participants were medication-free both before and during the tDCS sessions. None had a current or past history of traumatic head injury, seizures, autism, conduct disorder, or any other severe mental or neurological disorder, as determined through a clinical interview conducted by a psychiatrist or clinical psychologist. Participants had normal IQ scores, with an exclusion criterion of IQ below 80 or above 130. The study procedures adhered to the ethical standards of the \u003cem\u003eDeclaration of Helsinki\u003c/em\u003e (1975, revised in 2013) and were approved by the local ethics committee at Shahid Beheshti University. The task was presented on a laptop with a 15.600 screen and the viewing distance from the monitor was approximately 50 cm. this task had an initial stage to make participants familiar with the task.\u003c/p\u003e\n\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003eChocolate delay discounting task (CDDT)\u003c/h2\u003e\n \u003cp\u003eThe delay discounting task requires participants to choose between a small, immediate reward and a larger reward that is delayed. During task performance, both the length of the delay and the size of the postponed reward increase. The individual\u0026rsquo;s turning point in decision-making\u0026mdash;where they shift preference between immediate smaller rewards and delayed larger rewards\u0026mdash;makes this task a valuable tool for assessing. Instead of monetary choices, as chocolate serves as a well-suited primary reward for children \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. The task was presented on a laptop with a 15.6-inch screen, and the viewing distance reward processing. In this study, we used chocolate images (Fig. 1). Figure was approximately 50 cm. To ensure participants understood the task, an initial familiarization stage was included. This task has previously been used with children with ADHD as an intervention-sensitive measure \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. The immediate reward consisted of one chocolate bar, while the delayed rewards comprised two, five, ten, and twenty chocolate bars, available after 1 day, 2 days, 3 days, 5 days, 1 week, and 1 month, respectively. The main variable of this task is the rate of discounting (K), calculated using the function: Vi\u0026thinsp;=\u0026thinsp;Ai / (1\u0026thinsp;+\u0026thinsp;Ki \u0026times; Di), where Vi represents the present value of the reward, Ai is the delayed reward, Di is the delay, and Ki is the discount rate \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. The discounting rates (K values) were computed separately for each condition, and the mean discount rate (Kmean) was derived by averaging them. Task completion took approximately 5 minutes per participant.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003etDCS protocol\u003c/h3\u003e\n\u003cp\u003eThe ActivaDose transcranial stimulator (ActivaTek Inc., USA) was used for brain stimulation. A direct current of 1 mA was applied through saline-soaked sponge electrodes measuring 24 cm\u0026sup2; (4 \u0026times; 6 cm) for 20 minutes, with a 15-second ramp-up and 15-second ramp-down period. The anodal electrode was positioned over the right dorsolateral prefrontal cortex (rdlPFC; F4) according to the 10\u0026ndash;20 EEG international system and cathodal electrode over the left arm (Fig.\u0026nbsp;2), and stimulation was administered over 10 sessions.\u003c/p\u003e\n\u003cp\u003eAt the end of each session, participants were asked about any side effects experienced during stimulation using a standardized side effect survey. The experimenter responsible for administering tDCS was not blinded to the study hypotheses or tDCS condition (active vs. sham). For sham stimulation, the electrical current was ramped up for 30 seconds to produce the same initial sensation as in the active condition, after which it was turned off without the participants\u0026rsquo; awareness \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eProcedure.\u003c/strong\u003e After obtaining written informed consent from the parents of children with ADHD, participants were randomly assigned to two groups: the tDCS group and the control group. Zeinab Agahie the first author allocated participant in tDCS group or Sham. Assessments were conducted in three separate sessions: pre-intervention (immediately before the first experimental session), post-intervention (immediately after the final session), and a 2-month follow-up assessment.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStudy design.\u003c/strong\u003e Participants in the electrical stimulation groups were blinded to their stimulation condition (i.e., active vs. sham). Stimulation sessions were conducted in a quiet room, three times per week on non-consecutive days, to prevent carry-over effects. All computerized tasks, including stimuli presentation, were controlled by a laptop with a 15.6-inch screen, positioned at a viewing distance of approximately 50 cm. Before the experiment, participants received instructions on the CDD task, with detailed written instructions displayed on the screen before the task began. We used Mix Anova to analyze data.\u003c/p\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003eStatistical analysis\u003c/h2\u003e\n \u003cp\u003eThe data collected in this study analyzed using SPSS version 21. The primary outcome measure, the delay discounting rate, quantified using the k-index. To assess the effects of tDCS on delay discounting, a mixed-design ANOVA conducted. The independent variable was group (active tDCS vs. sham), and the within-subjects factor were time (baseline, post-intervention, and follow-up) The level of significance for all statistical tests set at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eAll participants tolerated the stimulation well, with no significant side effects reported during or after the sessions, confirming the safety and tolerability of the procedure. No adverse events or unintended effects were observed or reported by participants or their parents during the course of the study.\u003c/p\u003e\n\u003cp\u003eNo significant group differences were found in demographic characteristics (see Table\u0026nbsp;1). The mean and standard deviation of the intervention (tDCS) and sham conditions for each K index\u0026mdash;2 chocolates, 5 chocolates, 10 chocolates, 20 chocolates, and the total K index\u0026mdash;are presented in Table\u0026nbsp;2.\u003c/p\u003e\n\u003cp\u003eThe results of the ANOVA revealed a significant interaction between group and time for the total K index (F\u0026thinsp;=\u0026thinsp;4.3, p\u0026thinsp;\u0026lt;\u0026thinsp;0.02, \u0026eta;p\u0026sup2; = 0.18). However, neither the main effect of group nor the main effect of time showed significant differences (see Table 3). A similar pattern was observed for the 20-chocolate K index, where the interaction between group and time was significant (F\u0026thinsp;=\u0026thinsp;3.2, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05, \u0026eta;p\u0026sup2; = 0.14), but the main effects of group and time were not significant.\u003c/p\u003e\n\u003cp\u003eFor the 10-chocolate K index, no significant differences were found in the interaction between group and time, nor in the main effects of group or time. Likewise, no significant differences were observed for the 5-chocolate K index or the 2-chocolate K index.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe results of our study suggest that anodal tDCS over the right dorsolateral prefrontal cortex (rdlPFC) increases the likelihood of choosing delayed rewards in children with ADHD compared to sham stimulation. In cognitive theories of ADHD, the dlPFC, a critical region for executive functions, is known to be hypoactive in individuals with ADHD, leading to functional deficits \u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e,\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e. Our findings support prior research demonstrating the essential role of the dlPFC in executive functions and cognitive control \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan additionalcitationids=\"CR41 CR42\" citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAdditionally, our results align with previous studies showing that anodal tDCS over the right dlPFC significantly enhances cognitive control \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e,\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e and increases participants' preference for larger, delayed rewards compared to sham stimulation \u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eNeural Mechanisms of Delay Discounting.\u003c/b\u003e Delay discounting involves two key neural systems, as demonstrated by functional magnetic resonance imaging (fMRI) studies in healthy adults. The immediate reward system, responsible for reward processing, includes the ventral striatum, medial orbitofrontal cortex (mOFC), medial prefrontal cortex (mPFC), and posterior cingulate cortex (PCC). In contrast, the delayed reward system, associated with cognitive control, engages the dorsolateral prefrontal cortex (dlPFC), ventrolateral prefrontal cortex (vlPFC), and lateral orbitofrontal cortex (lOFC) \u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eIn a previous study, we targeted the reward-processing system using anodal right ventromedial prefrontal cortex (vmPFC) stimulation and cathodal left dlPFC stimulation \u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. In contrast, the current study focused on the cognitive control system by stimulating the rdlPFC. Given that the dlPFC plays a central role in cognitive control, our findings suggest that its hypoactivity is linked to an increased tendency for delay discounting in children with ADHD. These results align with neuroimaging studies demonstrating that reduced dlPFC activation correlates with impaired executive function and increased impulsivity \u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e,\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eMoreover, previous studies have shown that the severity of hyperactive/impulsive symptoms in ADHD is positively correlated with delay discounting rates \u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. The rdlPFC is crucial for impulse control, decision-making, and self-regulation. Its role in inhibitory control and risk assessment suggests that modulating this region via tDCS could provide a therapeutic avenue for addressing impulsivity-related disorders, including ADHD, addiction, and obesity \u003csup\u003e\u003cspan additionalcitationids=\"CR31 CR32\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e,\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e. Our findings support this perspective, highlighting that anodal tDCS over the rdlPFC can effectively modulate delay discounting, potentially offering therapeutic benefits for impulsivity and decision-making deficits.\u003c/p\u003e \u003cp\u003e \u003cb\u003eLong-Term Effects and Neuroplasticity.\u003c/b\u003e A key feature of this study was the inclusion of a follow-up session to evaluate the long-term effects of tDCS. While most studies focus on single-session or short-term interventions, assessing executive function (EF) during, before, or immediately after stimulation \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e,\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e,\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e, our study uniquely examined delay discounting two months post-stimulation. This approach allowed us to assess the lasting impact of the intervention beyond the stimulation period.\u003c/p\u003e \u003cp\u003eAdditionally, this study focused on children, considering that childhood and adolescence are critical periods of neurodevelopment and heightened neuroplasticity. Early interventions can leverage neuroplasticity to establish new pathways that compensate for deficits. The earlier the intervention occurs, the greater its potential impact due to the brain's increased plasticity during these formative years \u003csup\u003e\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cb\u003eLimitations and Future Directions\u003c/b\u003e. Despite the promising findings of this study, several limitations should be acknowledged. One key limitation was the reduction in sample size after the follow-up sessions, which may have influenced the statistical power and reliability of the results. Future studies should aim to include a larger sample size to enhance the generalizability of the findings. Additionally, the researcher conducting tDCS was not blinded to the study conditions, which could introduce potential bias in the experimental procedure. Implementing a double-blind design in future research would improve methodological rigor and reduce potential experimenter effects. Another important consideration is the duration and frequency of the stimulation protocol. While our study applied ten tDCS sessions, future studies should explore whether increasing the number of sessions leads to more pronounced and lasting effects. Moreover, the current study targeted the cognitive control system by stimulating the right dlPFC, whereas previous studies have also focused on the reward-processing system \u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e. Future research should compare these two approaches or investigate the combined effects of stimulating both the cognitive control and reward-processing networks to determine the most effective intervention strategy for reducing delay discounting in individuals with ADHD. Finally, while this study focused on children, future research should examine whether similar effects can be observed in adolescents and adults with ADHD. Given that brain plasticity changes with age, understanding how age-related differences influence the effectiveness of tDCS on delay discounting would provide valuable insights into optimizing intervention strategies. By addressing these limitations and expanding the scope of research, future studies can further refine the application of non-invasive brain stimulation as a potential therapeutic tool for improving decision-making and impulse control in individuals with ADHD.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eOverall, tDCS represents a promising tool for modulating delay discounting through targeted stimulation of the dlPFC. By enhancing cognitive control and reducing impulsivity, tDCS has the potential to serve as an effective intervention for individuals with difficulty in time perception and impulse control. However, further research\u0026mdash;including comparative studies with larger sample sizes\u0026mdash;is necessary to fully understand its effects across different populations and contexts.\u003c/p\u003e\n"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research project received no external financial support.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLuman, M., Tripp, G. \u0026amp; Scheres, A. 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Transcranial direct current stimulation over dorsolateral prefrontal cortex modulates risk-attitude in motor decision-making. \u003cem\u003eFront Hum Neurosci\u003c/em\u003e \u003cstrong\u003e13\u003c/strong\u003e, 297 (2019).\u003c/li\u003e\n\u003cli\u003eXiong, G. \u003cem\u003eet al.\u003c/em\u003e Modulating activity in the prefrontal cortex changes intertemporal choice for loss: A transcranial direct current stimulation study. \u003cem\u003eFront Hum Neurosci\u003c/em\u003e \u003cstrong\u003e13\u003c/strong\u003e, 167 (2019).\u003c/li\u003e\n\u003cli\u003eGoreishi, A. \u0026amp; Shajari, Z. Substance Abuse among Students of Zanjan\u0026rsquo;s Universities (Iran): A Knot of Today\u0026rsquo;s Society. \u003cem\u003eAddiction \u0026amp; Health\u003c/em\u003e \u003cstrong\u003e5\u003c/strong\u003e, 66 (2013).\u003c/li\u003e\n\u003cli\u003eChen, Z., Wang, X., Zhang, S. \u0026amp; Han, F. Neuroplasticity of children in autism spectrum disorder. \u003cem\u003eFront Psychiatry\u003c/em\u003e \u003cstrong\u003e15\u003c/strong\u003e, 1362288 (2024).\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003e\u003cstrong\u003eTable 1:\u0026nbsp;\u003c/strong\u003eDemographic characteristics and ADHD- rating of participants\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"482\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eVariables\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cu\u003etDCS ,\u0026nbsp;\u003cbr\u003e\u0026nbsp;M (SD)\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cu\u003eSham,\u0026nbsp;\u003cbr\u003e\u0026nbsp;M (SD)\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eANOVA Statistics\u003cbr\u003e\u0026nbsp; (F, p- value)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp;Age (Years)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e8.9(1.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e9(1.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e.025, .786\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp;Education (Years)\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.6(2.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3(1.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e.594, 449\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026nbsp; \u0026nbsp;Gender (Female, Male)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e6,5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e5, 9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cem\u003eAbbreviation:\u0026nbsp;\u003c/em\u003e\u003cstrong\u003etDCS: transcranial direct current stimulation, M: mean, SD: standard deviation, F: female, M: male.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cstrong\u003eTable 2.\u0026nbsp;\u003c/strong\u003eDescriptive Statistics (Mean, Standard Deviation) of chocolate delay discounting task(CDDT)\u003c/strong\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSituation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" valign=\"top\" style=\"width: 227px;\"\u003e\n \u003cp\u003e\u003cstrong\u003etDCS\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eM(SD)\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"3\" valign=\"top\" style=\"width: 265px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSham\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eM(SD)\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 56px;\"\u003e\n \u003cp\u003ePre test\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003ePost test\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 86px;\"\u003e\n \u003cp\u003eFollow up\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003ePre test\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003ePost test\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eFollow up\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2 chocolate K\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 56px;\"\u003e\n \u003cp\u003e1.03(1.28)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e.36(.38)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 86px;\"\u003e\n \u003cp\u003e.60(.44)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e1.03(1.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e.63(.30)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e.59(.34)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e5 chocolate K\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 56px;\"\u003e\n \u003cp\u003e1.8(1.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e1.2(1.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 86px;\"\u003e\n \u003cp\u003e1(1.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e2.08(1.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e1.9(1.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e1.9(1.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e10 chocolate K\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 56px;\"\u003e\n \u003cp\u003e4.4(4.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e3.5(3.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 86px;\"\u003e\n \u003cp\u003e2.1(2.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e5.1(3.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e4.4(3.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e6.1(3.5)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e20 chocolate K\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 56px;\"\u003e\n \u003cp\u003e5.9(7.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e4.2(5.6)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 86px;\"\u003e\n \u003cp\u003e2.03(2.01)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e4.5(7.2)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e3.8(5.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e8.3(8.7)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal K index\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 56px;\"\u003e\n \u003cp\u003e3.3(2.06)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e2.3(2.4)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 86px;\"\u003e\n \u003cp\u003e1.4(1.06)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 96px;\"\u003e\n \u003cp\u003e3.2(2.3)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e2.7(2.1)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e4.2(2.9)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cem\u003eAbbreviation:\u0026nbsp;\u003c/em\u003e\u003cstrong\u003etDCS: transcranial direct current stimulation, M: mean, SD: standard deviation, CDD: chocolate delay discounting task\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cstrong\u003eTable 3.\u003c/strong\u003e Results of the Repeated Measures ANOVAs for Effects of tDCS Conditions (Sham/Anodal rDLPFC)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"642\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eMeasures\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"4\" valign=\"top\" style=\"width: 151px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTime Effect\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 17px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"4\" valign=\"top\" style=\"width: 172px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGroup Effect\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 21px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd colspan=\"4\" valign=\"top\" style=\"width: 168px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTime * Group\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e\u003cstrong\u003edf\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 45px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eF\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ep\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 47px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026eta;p2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 17px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e\u003cstrong\u003edf\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eF\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ep\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026eta;p2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 21px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28px;\"\u003e\n \u003cp\u003e\u003cstrong\u003edf\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eF\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 38px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ep\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u0026eta;p2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e2 chocolate K\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 45px;\"\u003e\n \u003cp\u003e2.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 47px;\"\u003e\n \u003cp\u003e.13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 17px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003e.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e.009\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 21px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44px;\"\u003e\n \u003cp\u003e.23\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 38px;\"\u003e\n \u003cp\u003e.79\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e.01\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e5 chocolate K\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 45px;\"\u003e\n \u003cp\u003e.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 47px;\"\u003e\n \u003cp\u003e..04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 17px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003e1.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e.20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 21px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44px;\"\u003e\n \u003cp\u003e.315\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 38px;\"\u003e\n \u003cp\u003e.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e.01\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e10 chocolate K\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 45px;\"\u003e\n \u003cp\u003e.312\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e.73\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 47px;\"\u003e\n \u003cp\u003e.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 17px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003e3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 21px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44px;\"\u003e\n \u003cp\u003e1.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 38px;\"\u003e\n \u003cp\u003e.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e.08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e20 chocolate K\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 45px;\"\u003e\n \u003cp\u003e.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 47px;\"\u003e\n \u003cp\u003e.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 17px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003e.53\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e.47\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 21px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44px;\"\u003e\n \u003cp\u003e3.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 38px;\"\u003e\n \u003cp\u003e.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e.14\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTotal K index\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 18px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 45px;\"\u003e\n \u003cp\u003e.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e.39\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 47px;\"\u003e\n \u003cp\u003e.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 17px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 30px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 43px;\"\u003e\n \u003cp\u003e1.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 41px;\"\u003e\n \u003cp\u003e.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 21px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 28px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 44px;\"\u003e\n \u003cp\u003e4.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 38px;\"\u003e\n \u003cp\u003e.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 58px;\"\u003e\n \u003cp\u003e.18\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"ADHD, delay discounting, cognitive control, transcranial direct current stimulation (tDCS), dorsolateral prefrontal cortex (dlPFC), impulsivity","lastPublishedDoi":"10.21203/rs.3.rs-6330387/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6330387/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eIndividuals with Attention-Deficit/Hyperactivity Disorder (ADHD) often exhibit delay discounting, a preference for smaller immediate rewards over larger delayed rewards, which is linked to executive function deficits and impulsive decision-making. The right dorsolateral prefrontal cortex (rdlPFC) plays a crucial role in cognitive control and impulse regulation, making it a potential target for non-invasive brain stimulation interventions.\u003c/p\u003e\u003ch2\u003eObjective\u003c/h2\u003e \u003cp\u003eThis study aimed to investigate the effects of anodal transcranial direct current stimulation (tDCS) over the rdlPFC on delay discounting in children with ADHD. We hypothesized that active tDCS would enhance cognitive control, reducing impulsivity and increasing the selection of delayed rewards.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eUsing a single-blind, randomized parallel-group design, twenty-one children with ADHD (aged 7\u0026ndash;12 years) were randomly assigned to either the active tDCS or sham stimulation group. The intervention consisted of 10 sessions of 1 mA anodal tDCS applied to the rdlPFC over three weeks. Participants completed a Chocolate Delay Discounting Task (CDDT) at three time points: pre-intervention, post-intervention, and two-month follow-up. A mixed ANOVA was conducted to examine the effects of tDCS on delay discounting rates (K index) across conditions.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eThe interaction between group and time was significant for the total K index (F\u0026thinsp;=\u0026thinsp;4.3, p\u0026thinsp;\u0026lt;\u0026thinsp;0.02, ηp\u0026sup2; = 0.18) and the 20-chocolate K index (F\u0026thinsp;=\u0026thinsp;3.2, p\u0026thinsp;\u0026lt;\u0026thinsp;0.05, ηp\u0026sup2; = 0.14), indicating that anodal tDCS increased the likelihood of selecting delayed rewards compared to the sham condition. However, the main effects of group and time were not significant. No significant differences were observed for the 10-, 5-, and 2-chocolate K indices.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eThese findings suggest that anodal tDCS over the rdlPFC reduce delay discounting in children with ADHD, particularly in high-reward scenarios. Given the long-term follow-up results, tDCS could serve as a promising intervention for addressing impulsivity-related deficits in ADHD.\u003c/p\u003e","manuscriptTitle":"Modulating Delay Discounting in ADHD: A Multi-Sessional tDCS Intervention","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-13 06:42:57","doi":"10.21203/rs.3.rs-6330387/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-02T19:25:06+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-06T07:15:16+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"180431627905700307720782673287466766420","date":"2026-01-24T19:54:24+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"114403468240074432165584509401688044196","date":"2026-01-11T21:36:56+00:00","index":"hide","fulltext":""},{"type":"editorInvited","content":"","date":"2025-11-14T19:24:11+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-08T01:14:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"60742255007826821886915691984826699276","date":"2025-06-25T05:11:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"180076333483122593907845865919183054696","date":"2025-06-18T02:30:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"264189009894492314765332386727090657644","date":"2025-05-07T06:57:11+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-05-06T14:39:01+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-04-25T06:14:50+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-04-20T09:05:28+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-04-20T09:04:18+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"e0b47723-6468-4293-9846-98e177edc8fa","owner":[],"postedDate":"May 13th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":48251921,"name":"Biological sciences/Neuroscience"},{"id":48251922,"name":"Biological sciences/Psychology"}],"tags":[],"updatedAt":"2026-05-19T14:23:30+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-13 06:42:57","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6330387","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6330387","identity":"rs-6330387","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}