EEG Alpha and Theta Power Modulation During Fragrance Exposure: Insights into the Neural Correlates of Calmness

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This study investigates electroencephalographic (EEG) changes in alpha (8–13 Hz) and theta (4–8 Hz) power density following exposure to different fragrance conditions among healthy male participants. EEG signals were recorded using the Unicorn Hybrid 8-channel system at frontal (Fz), parietal (Pz), and parieto-occipital (PO7, PO8) sites before and after controlled fragrance exposure. Power-spectral analysis was conducted to quantify changes in alpha and theta activity associated with calm emotional states. The results revealed differential modulation of alpha and theta power density across cortical regions following fragrance exposure, suggesting that specific olfactory inputs can alter neural oscillations indicative of calmness. These findings provide electrophysiological evidence for the neural basis of fragrance-induced calmness and contribute to the broader understanding of olfactory–cortical interactions in emotion regulation. Electroencephalography (EEG) Brain Waves Fragrance Calmness Olfactory Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 1 Introduction The human olfactory system plays an essential role in modulating emotional and cognitive functions through neural pathways that link olfactory structures with limbic and cortical areas (Bothwell et al., 2023). Odor stimuli can influence attention, memory, and emotional regulation by activating interconnected regions such as the amygdala, orbitofrontal cortex, and medial prefrontal cortex (Kontaris et al., 2020; Rolls, 2023). Among these processes, the experience of calmness or relaxation has been strongly associated with specific olfactory inputs, as fragrances can evoke autonomic and cortical responses linked to reduced arousal and emotional stability (Ahmad & Pratap, 2024; Sowndhararajan & Kim, 2016). Electroencephalography (EEG) provides a noninvasive method to capture frequency-specific brain oscillations with high temporal precision, making it suitable for detecting subtle neural changes during olfactory-induced calmness (Chmiel & Malinowska, 2025). The alpha (8–13 Hz) and theta (4–8 Hz) bands are particularly sensitive to shifts in cortical states associated with relaxation, internal attention, and emotional regulation (Dobrakowski et al., 2020). Increased alpha activity has been linked to calm and restful states, whereas theta activity is often associated with emotional integration and meditative focus (Katyal & Goldin, 2021). Thus, analysis of alpha and theta power density serves as an objective electrophysiological indicator of calmness in response to sensory modulation. While behavioral and autonomic studies have demonstrated calming effects of fragrances, there remains limited electrophysiological evidence quantifying how olfactory stimulation alters alpha and theta power density across multiple cortical regions. Previous work has often relied on subjective mood ratings, whereas EEG-based analyses can offer direct neural markers of calmness. Therefore, this study aims to quantify changes in EEG alpha and theta power density before and after fragrance exposure among healthy participants. By focusing on the objective measurement of neural oscillations associated with calmness, this work contributes to a clearer understanding of how olfactory stimuli influences large-scale cortical dynamics linked to emotional regulation and cognitive processing. 2 Materials and Methods 2.1 Participants Twenty-four healthy male university students (aged 18–25 years) from local higher education institutions in Malaysia were recruited through purposive sampling. All participants were right-handed, with normal olfactory ability, and reported no history of neurological disorders, head injuries, nasal blockage, or fragrance allergies. Participants were screened for eligibility before the experiment, and written informed consent was obtained. The study was approved by the USM Human Research Ethics Committee (USM/JEPeM/KK/24121070), and all procedures were conducted in accordance with the ethical standards of the Declaration of Helsinki (World Medical Association, 2025). 2.2 Fragrance Stimuli Three commercial fragrances (Fragrance A, Fragrance B, and Fragrance C) and one odorless placebo were used as olfactory stimuli. The samples were prepared at low concentrations to ensure safety and prevent olfactory fatigue. Participants were instructed to smell naturally, not to sniff, during exposure. Fragrances were provided at a low concentration via a conventional diffuser technique, following olfactory research standards. 2.3 EEG Recording and Setup EEG data were recorded using the Unicorn Hybrid 8-channel EEG system. The system consists of eight active dry electrodes integrated into a wireless headset. EEG recording was performed using Unicorn Hybrid EEG software to monitor brain activity in real-time. The analysis focused on four electrodes (Fz, Pz, PO7, and PO8) representing the frontal, parietal, and parieto-occipital cortical regions. These areas are functionally related to attention, sensory integration, and emotional regulation, as described in previous neurophysiological research. Figure 1 depicts the Unicorn Hybrid Black EEG System, featuring the headset aligned with the attached electrode. Figure 1 Unicorn Hybrid Black EEG System (Pontifex & Coffman, 2023) 2.4 Procedure The experiment was conducted in a quiet, temperature-controlled room to minimize external interference. Participants were seated comfortably and fitted with the EEG headset. Each session began with a one-minute baseline recording, followed by one minute of fragrance exposure, and one minute of post-exposure recording. The four conditions (Fragrance A, Fragrance B, Fragrance C, and placebo) were presented in randomized order, with sufficient rest intervals between exposures to prevent olfactory adaptation. Participants were instructed to remain still, relaxed, and to keep their eyes closed throughout data collection. The overall experimental workflow is illustrated in Fig. 2 , summarizing the standardized sequence of participant screening, EEG setup, baseline recording, fragrance exposure, and post-exposure data acquisition. 2.5 Data Processing and Analysis EEG data were processed using the Brain Analyzer software. Raw EEG signals were filtered between 1–30 Hz to remove artifacts and analyzed for the alpha (8–13 Hz) and theta (4–8 Hz) frequency bands. Power spectral density (PSD) was computed for each electrode to quantify cortical activity changes related to calmness and attention. Mean PSD values of alpha and theta, before and after fragrance exposure for each participant across four selected electrodes, were compared using paired-sample t-tests performed in IBM SPSS Statistics. Statistical significance was defined at p < 0.05. 3 Results 3.1 EEG Alpha and Theta Power Density After Exposure to Fragrance A, B, C, and Placebo The following bar charts (Fig. 3 – 6 ) show the average alpha (8–13 Hz) and theta (4–8 Hz) power density values, expressed in µV²/Hz, across the four selected electrodes (Fz, Pz, PO7, and PO8) before and after exposure to each fragrance group. These visualizations illustrate how EEG brainwave activity changes in response to different aromatic stimuli. Bars represent the group mean values, and error bars represent the standard deviation (SD) of the mean. 3.2 EEG Alpha and Theta Power Density Before and After Fragrance Exposure Across Groups Table 1 presents the mean alpha and theta power density values (µV²/Hz) before and after exposure to each fragrance condition, together with mean differences and p-values derived from paired-sample t-tests. Statistical analysis was performed using SPSS Statistics software. Results with a p-value of less than 0.05 were considered statistically significant, indicating that the observed EEG changes were unlikely due to random variation and were likely caused by fragrance exposure. A notable increase in alpha power was observed following exposure to Fragrance A (Floral & Fruity) (p = 0.032) and Fragrance B (Spices & Wood) (p = 0.008), suggesting enhanced cortical relaxation during these conditions. In contrast, alpha power changes for Fragrance C (Citrus-Floral) (p = 0.145) and Placebo (p = 0.994) were not statistically significant. Theta band power showed no significant differences across any condition, although Fragrance A exhibited a mild reduction trend (p = 0.078). Table 1 EEG Alpha and Theta Power Density Before and After Fragrance Exposure Across Groups Fragrance Type Wave Mean Before (µV²/Hz) Mean After (µV²/Hz) Mean Difference p-value Fragrance A (Floral & Fruity) Alpha 33.7015 37.8538 + 4.1523 0.032 Theta 75.8912 71.8238 − 4.0673 0.078 Fragrance B (Spices & Wood) Alpha 34.1234 39.4611 + 5.3377 0.008 Theta 71.6899 71.6257 − 0.0642 0.966 Fragrance C (Citrus-Floral) Alpha 35.2839 37.1952 + 1.9113 0.145 Theta 69.0380 66.0841 − 2.9539 0.353 Placebo Alpha 34.1655 34.1667 + 0.0012 0.994 Theta 72.2503 72.1848 − 0.0655 0.592 3.3 Interpretation of EEG Alpha and Theta Power Density Changes The data analysis revealed that Fragrance B (Spices & Wood) produced a statistically significant increase in alpha wave power from pre- to post-exposure (p = 0.008), suggesting enhanced relaxation and calmness in response to this scent. No significant change was observed in theta power (p = 0.966). This finding highlights a potential calming effect of Fragrance B within its group, warranting further investigation to determine whether similar effects occur with other fragrance types. Fragrance A (Floral & Fruity) also demonstrated a notable increase in alpha activity (mean difference = + 4.1523 µV²/Hz) with a p-value at the threshold of significance (p = 0.032), indicating a possible calming response. However, the decrease in theta power (− 4.0673 µV²/Hz, p = 0.078) was not statistically significant, suggesting that the effect was primarily localized to the alpha frequency band. In contrast, Fragrance C (Citrus-Floral) did not yield statistically meaningful changes in either frequency band. Although minor shifts were observed, an increase in alpha and a decrease in theta with the respective p-values (0.145 and 0.353) indicate non-significant changes, implying minimal or inconsistent effects on cortical relaxation. As expected, the placebo group exhibited no significant changes in alpha (p = 0.994) or theta power (p = 0.592). These results help validate the reliability of the findings in the experimental groups and minimize the influence of confounding factors. 3.4 Topographical Distribution of Alpha and Theta Band Power Following the statistical analysis, topographical maps were generated to visually represent the spatial distribution of alpha and theta power across the scalp. These maps further illustrate the EEG changes observed after fragrance exposure and confirm the alterations in cortical activity patterns. Figure 7 displays the distribution of alpha activity across the scalp for each condition, both before and after fragrance exposure. An increase in alpha power is visually observable, particularly following exposure to Fragrance B, indicating a pronounced calming effect. Fragrance A and Fragrance C also showed moderate increases in alpha power, while the placebo condition demonstrated minimal visual change. Figure 8 illustrates the theta band distribution, where a general decrease in theta power was observed following fragrance exposure. The most notable reductions occurred under Fragrance A and Fragrance C, suggesting reduced drowsiness or mental disengagement (Daneshgar et al., 2025). In contrast, Fragrance B showed minimal theta change, indicating a calming effect without inducing drowsiness (Bonakdarpour et al., 2023). The placebo condition again showed no meaningful differences across the scalp. Overall, spatial visualization supports the quantitative EEG findings, showing that fragrance exposure, particularly Fragrance B, elicited measurable changes in cortical activity associated with calmness and alert relaxation. 4 Discussion A. Effects of Fragrance A (Floral–Fruity) on EEG Alpha and Theta Activity The EEG results showed that Fragrance A (Floral–Fruity) was associated with a significant increase in alpha power and a reduction in theta power from pre- to post-exposure. This pattern is consistent with previous findings, where enhanced alpha activity is linked to relaxed wakefulness and internalized attention (Deshmukh, 2023). The olfactory characteristics of Fragrance A, which combine floral and fruity notes, may evoke emotional comfort or mood stabilization through the engagement of limbic–cortical pathways involved in affective regulation. The increase in alpha activity suggests that this fragrance profile contributes to a sense of calmness or relaxed alertness, although additional comparisons across scent categories would be necessary to determine its distinctiveness. B. Effects of Fragrance B (Spices & Wood) on EEG Alpha and Theta Activity Fragrance B (Spices & Wood) elicited the most prominent neural effect among all conditions, producing a significant increase in alpha power (p = 0.008) without a corresponding change in theta activity (p = 0.966). This EEG profile indicates enhanced cortical relaxation while maintaining mental alertness, a combination typically associated with calm attention. The olfactory profile of Fragrance B includes woody and resinous compounds such as Cedrol and Thujopsene, both of which have been reported to exhibit sedative and anxiolytic properties (Maduka et al., 2024). These findings provide electrophysiological evidence that complex fragrances containing these compounds can modulate brain activity linked to calmness. Further studies incorporating chemical composition analyses and cross-condition comparisons could clarify whether this effect is unique to woody–spice fragrances or generalizable to other calming scents. C. Effects of Fragrance C (Citrus–Floral) on EEG Alpha and Theta Activity Exposure to Fragrance C (Citrus–Floral) resulted in minor, non-significant increases in alpha power and slight reductions in theta power. This limited EEG response suggests that this fragrance type may induce a more alert or invigorating state rather than a calm one. Previous studies have indicated that citrus-based scents such as limonene and linalool can enhance arousal and attentional readiness (Eissa, 2024). Thus, the weaker modulation of alpha and theta activity observed here may reflect the stimulating properties of citrus–floral compositions, aligning with their common association with freshness and mental alertness rather than relaxation. D. Effects of Placebo on EEG Alpha and Theta Activity The placebo condition displayed no statistically significant changes in alpha (p = 0.994) or theta power (p = 0.592), confirming that the EEG variations observed in the fragrance groups were attributable to olfactory stimulation rather than experimental artifacts or time-dependent effects. The stability of neural activity in the placebo group supports the reliability of the experimental design and validates the role of the fragrances as the primary modulators of EEG responses. The absence of significant cortical changes under this condition emphasizes the functional importance of olfactory input in eliciting measurable neurophysiological effects, distinguishing true sensory-driven modulation from baseline neural variability. 5 Conclusion This study explored the neurophysiological effects of commercial fragrances on EEG activity in healthy male participants. Power density analysis revealed that Fragrance B (Spices & Wood) produced the largest increase in alpha power (+ 5.34 µV²/Hz) accompanied by a slight decrease in theta power (− 0.06 µV²/Hz), suggesting enhanced cortical calmness without drowsiness. Fragrance A (Floral–Fruity) also increased alpha power (+ 4.15 µV²/Hz) and decreased theta power (− 4.06 µV²/Hz), indicating a moderate relaxation response. In contrast, Fragrance C (Citrus–Floral) produced smaller changes in alpha (+ 1.19 µV²/Hz) and theta (− 2.95 µV²/Hz), while the placebo showed no significant EEG variations. Overall, these findings provide objective electrophysiological evidence that changes in alpha power may serve as a reliable neural indicator of calmness following fragrance exposure. The present study contributes to understanding how distinct olfactory compounds interact with cortical networks involved in emotional and attentional control. Future research could expand on these results by including female participants, employing larger sample sizes, and examining the long-term or cross-modal effects of fragrance exposure on neural oscillatory dynamics. Declarations Acknowledgments The authors extend their sincere gratitude to the Faculty of Science and Technology, Universiti Sains Islam Malaysia (USIM), the Brain & Behaviours Research Group (BBRG), and Sugarbomb Sdn. Bhd. for their invaluable support and collaboration throughout this research. Funding This research was supported by the USIM Research Grant (PPPI/BM/FST/USIM/113823). Conflict of Interest The authors declare that there are no conflicts of interest regarding the publication of this paper. Ethical Approval This research was conducted in accordance with the principles of the Declaration of Helsinki and was approved by the Ethical Committee USM (USM/JEPeM/KK/24121070). References Ahmad, S., & Pratap, P. D. (2024). 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10:02:14","extension":"xml","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":44385,"visible":true,"origin":"","legend":"","description":"","filename":"9537e1683da44157bf857ece14729d7a1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8073748/v1/20f0cf64287d4ecaa5e8b8b1.xml"},{"id":96617451,"identity":"884dfdde-4a22-4327-8225-ea96388264eb","added_by":"auto","created_at":"2025-11-24 10:27:29","extension":"html","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":54411,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8073748/v1/e275de30b909917673e4f2de.html"},{"id":96708756,"identity":"1c0170a3-ae5c-41e1-91ab-2fb37d44c80f","added_by":"auto","created_at":"2025-11-25 10:05:22","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":309117,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eUnicorn Hybrid Black EEG System (Pontifex \u0026amp; Coffman, 2023)\u003c/em\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8073748/v1/4d346b1110c8f01c01fd50e4.png"},{"id":96617440,"identity":"6993680d-92f6-4bd4-bc21-5e1bca34a5ea","added_by":"auto","created_at":"2025-11-24 10:27:28","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":511271,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eSchematic of The Experimental Paradigm for the EEG Fragrance-Exposure Study\u003c/em\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8073748/v1/07cb9a26f26e71840494e660.png"},{"id":96708657,"identity":"96cab03a-6bc4-45be-9970-7c4fb6ac091a","added_by":"auto","created_at":"2025-11-25 10:04:57","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":143923,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eAlpha and Theta Power Density After Exposure to Fragrance A\u003c/em\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8073748/v1/33b3e173d267dbd568fe74cd.png"},{"id":96617442,"identity":"14d24421-171a-462d-8920-f42ab5689e52","added_by":"auto","created_at":"2025-11-24 10:27:28","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":145165,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eAlpha and Theta Power Density After Exposure to Fragrance B\u003c/em\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8073748/v1/0969acfbb6cd195c7b0995a5.png"},{"id":96617444,"identity":"fee4082c-d05c-410d-9334-552ac4d6f070","added_by":"auto","created_at":"2025-11-24 10:27:29","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":142225,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eAlpha and Theta Power Density After Exposure to Fragrance C\u003c/em\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8073748/v1/710c8218a1526af79a1618f9.png"},{"id":96708300,"identity":"7ac408f6-d792-4c9d-a389-052b2275e89e","added_by":"auto","created_at":"2025-11-25 10:00:38","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":129912,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eAlpha and Theta Power Density After Placebo Exposure\u003c/em\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8073748/v1/6f73474369b50e6ea161460c.png"},{"id":96709708,"identity":"18ec12f7-decc-4526-8a83-0f130295dda4","added_by":"auto","created_at":"2025-11-25 10:09:33","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":2072329,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eTopographical distribution of alpha band power before and after exposure to Fragrance A, B, C, and Placebo. Warm colors (e.g., red, yellow) represent higher alpha power, typically associated with increased relaxation or reduced cortical activation.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8073748/v1/890c561599a426931a9e77c3.png"},{"id":96708724,"identity":"fb7af4cc-bc2e-4343-950b-eaa5c15c5638","added_by":"auto","created_at":"2025-11-25 10:05:17","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":2314425,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eTopographical distribution of theta band power before and after exposure to Fragrance A, B, C, and Placebo. Cooler tones (e.g., blue) reflect higher theta activity, often linked to drowsiness or emotional processing.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-8073748/v1/f0fc6b0c3979436fd9a7f9f7.png"},{"id":97673714,"identity":"d3da0b77-a49c-4b03-9343-b6f58c645438","added_by":"auto","created_at":"2025-12-08 09:41:08","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8364473,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8073748/v1/80097d4d-ee4b-4750-81e5-f17d9bd6e05e.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"EEG Alpha and Theta Power Modulation During Fragrance Exposure: Insights into the Neural Correlates of Calmness","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eThe human olfactory system plays an essential role in modulating emotional and cognitive functions through neural pathways that link olfactory structures with limbic and cortical areas (Bothwell et al., 2023). Odor stimuli can influence attention, memory, and emotional regulation by activating interconnected regions such as the amygdala, orbitofrontal cortex, and medial prefrontal cortex (Kontaris et al., 2020; Rolls, 2023). Among these processes, the experience of calmness or relaxation has been strongly associated with specific olfactory inputs, as fragrances can evoke autonomic and cortical responses linked to reduced arousal and emotional stability (Ahmad \u0026amp; Pratap, 2024; Sowndhararajan \u0026amp; Kim, 2016).\u003c/p\u003e\u003cp\u003eElectroencephalography (EEG) provides a noninvasive method to capture frequency-specific brain oscillations with high temporal precision, making it suitable for detecting subtle neural changes during olfactory-induced calmness (Chmiel \u0026amp; Malinowska, 2025). The alpha (8\u0026ndash;13 Hz) and theta (4\u0026ndash;8 Hz) bands are particularly sensitive to shifts in cortical states associated with relaxation, internal attention, and emotional regulation (Dobrakowski et al., 2020). Increased alpha activity has been linked to calm and restful states, whereas theta activity is often associated with emotional integration and meditative focus (Katyal \u0026amp; Goldin, 2021). Thus, analysis of alpha and theta power density serves as an objective electrophysiological indicator of calmness in response to sensory modulation.\u003c/p\u003e\u003cp\u003eWhile behavioral and autonomic studies have demonstrated calming effects of fragrances, there remains limited electrophysiological evidence quantifying how olfactory stimulation alters alpha and theta power density across multiple cortical regions. Previous work has often relied on subjective mood ratings, whereas EEG-based analyses can offer direct neural markers of calmness.\u003c/p\u003e\u003cp\u003eTherefore, this study aims to quantify changes in EEG alpha and theta power density before and after fragrance exposure among healthy participants. By focusing on the objective measurement of neural oscillations associated with calmness, this work contributes to a clearer understanding of how olfactory stimuli influences large-scale cortical dynamics linked to emotional regulation and cognitive processing.\u003c/p\u003e"},{"header":"2 Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Participants\u003c/h2\u003e\u003cp\u003eTwenty-four healthy male university students (aged 18\u0026ndash;25 years) from local higher education institutions in Malaysia were recruited through purposive sampling. All participants were right-handed, with normal olfactory ability, and reported no history of neurological disorders, head injuries, nasal blockage, or fragrance allergies. Participants were screened for eligibility before the experiment, and written informed consent was obtained. The study was approved by the USM Human Research Ethics Committee (USM/JEPeM/KK/24121070), and all procedures were conducted in accordance with the ethical standards of the Declaration of Helsinki (World Medical Association, 2025).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Fragrance Stimuli\u003c/h2\u003e\u003cp\u003eThree commercial fragrances (Fragrance A, Fragrance B, and Fragrance C) and one odorless placebo were used as olfactory stimuli. The samples were prepared at low concentrations to ensure safety and prevent olfactory fatigue. Participants were instructed to smell naturally, not to sniff, during exposure. Fragrances were provided at a low concentration via a conventional diffuser technique, following olfactory research standards.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 EEG Recording and Setup\u003c/h2\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eEEG data were recorded using the Unicorn Hybrid 8-channel EEG system. The system consists of eight active dry electrodes integrated into a wireless headset. EEG recording was performed using Unicorn Hybrid EEG software to monitor brain activity in real-time. The analysis focused on four electrodes (Fz, Pz, PO7, and PO8) representing the frontal, parietal, and parieto-occipital cortical regions. These areas are functionally related to attention, sensory integration, and emotional regulation, as described in previous neurophysiological research. Figure\u0026nbsp;1 depicts the Unicorn Hybrid Black EEG System, featuring the headset aligned with the attached electrode.\u003c/p\u003e\u003cp\u003e\u003cb\u003eFigure\u0026nbsp;1\u003c/b\u003e \u003cem\u003eUnicorn Hybrid Black EEG System (Pontifex \u0026amp; Coffman, 2023)\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Procedure\u003c/h2\u003e\u003cp\u003eThe experiment was conducted in a quiet, temperature-controlled room to minimize external interference. Participants were seated comfortably and fitted with the EEG headset. Each session began with a one-minute baseline recording, followed by one minute of fragrance exposure, and one minute of post-exposure recording. The four conditions (Fragrance A, Fragrance B, Fragrance C, and placebo) were presented in randomized order, with sufficient rest intervals between exposures to prevent olfactory adaptation. Participants were instructed to remain still, relaxed, and to keep their eyes closed throughout data collection. The overall experimental workflow is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003e, summarizing the standardized sequence of participant screening, EEG setup, baseline recording, fragrance exposure, and post-exposure data acquisition.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5 Data Processing and Analysis\u003c/h2\u003e\u003cp\u003eEEG data were processed using the Brain Analyzer software. Raw EEG signals were filtered between 1\u0026ndash;30 Hz to remove artifacts and analyzed for the alpha (8\u0026ndash;13 Hz) and theta (4\u0026ndash;8 Hz) frequency bands. Power spectral density (PSD) was computed for each electrode to quantify cortical activity changes related to calmness and attention. Mean PSD values of alpha and theta, before and after fragrance exposure for each participant across four selected electrodes, were compared using paired-sample t-tests performed in IBM SPSS Statistics. Statistical significance was defined at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e\u003c/div\u003e"},{"header":"3 Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.1 EEG Alpha and Theta Power Density After Exposure to Fragrance A, B, C, and Placebo\u003c/h2\u003e\u003cp\u003eThe following bar charts (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e6\u003c/span\u003e) show the average alpha (8\u0026ndash;13 Hz) and theta (4\u0026ndash;8 Hz) power density values, expressed in \u0026micro;V\u0026sup2;/Hz, across the four selected electrodes (Fz, Pz, PO7, and PO8) before and after exposure to each fragrance group. These visualizations illustrate how EEG brainwave activity changes in response to different aromatic stimuli. Bars represent the group mean values, and error bars represent the standard deviation (SD) of the mean.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.2 EEG Alpha and Theta Power Density Before and After Fragrance Exposure Across Groups\u003c/h2\u003e\u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e presents the mean alpha and theta power density values (\u0026micro;V\u0026sup2;/Hz) before and after exposure to each fragrance condition, together with mean differences and p-values derived from paired-sample t-tests. Statistical analysis was performed using SPSS Statistics software. Results with a p-value of less than 0.05 were considered statistically significant, indicating that the observed EEG changes were unlikely due to random variation and were likely caused by fragrance exposure.\u003c/p\u003e\u003cp\u003eA notable increase in alpha power was observed following exposure to Fragrance A (Floral \u0026amp; Fruity) (p\u0026thinsp;=\u0026thinsp;0.032) and Fragrance B (Spices \u0026amp; Wood) (p\u0026thinsp;=\u0026thinsp;0.008), suggesting enhanced cortical relaxation during these conditions. In contrast, alpha power changes for Fragrance C (Citrus-Floral) (p\u0026thinsp;=\u0026thinsp;0.145) and Placebo (p\u0026thinsp;=\u0026thinsp;0.994) were not statistically significant. Theta band power showed no significant differences across any condition, although Fragrance A exhibited a mild reduction trend (p\u0026thinsp;=\u0026thinsp;0.078).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003e\u003cem\u003eEEG Alpha and Theta Power Density Before and After Fragrance Exposure Across Groups\u003c/em\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFragrance Type\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWave\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMean Before (\u0026micro;V\u0026sup2;/Hz)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMean After (\u0026micro;V\u0026sup2;/Hz)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMean Difference\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003ep-value\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eFragrance A (Floral \u0026amp; Fruity)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAlpha\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e33.7015\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e37.8538\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e+\u0026thinsp;4.1523\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.032\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTheta\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e75.8912\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e71.8238\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026minus;\u0026thinsp;4.0673\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.078\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eFragrance B (Spices \u0026amp; Wood)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAlpha\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e34.1234\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e39.4611\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e+\u0026thinsp;5.3377\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.008\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTheta\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e71.6899\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e71.6257\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026minus;\u0026thinsp;0.0642\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.966\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eFragrance C (Citrus-Floral)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAlpha\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e35.2839\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e37.1952\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e+\u0026thinsp;1.9113\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.145\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTheta\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e69.0380\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e66.0841\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026minus;\u0026thinsp;2.9539\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.353\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003ePlacebo\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eAlpha\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e34.1655\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e34.1667\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e+\u0026thinsp;0.0012\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.994\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eTheta\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e72.2503\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e72.1848\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e\u0026minus;\u0026thinsp;0.0655\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e0.592\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Interpretation of EEG Alpha and Theta Power Density Changes\u003c/h2\u003e\u003cp\u003eThe data analysis revealed that Fragrance B (Spices \u0026amp; Wood) produced a statistically significant increase in alpha wave power from pre- to post-exposure (p\u0026thinsp;=\u0026thinsp;0.008), suggesting enhanced relaxation and calmness in response to this scent. No significant change was observed in theta power (p\u0026thinsp;=\u0026thinsp;0.966). This finding highlights a potential calming effect of Fragrance B within its group, warranting further investigation to determine whether similar effects occur with other fragrance types.\u003c/p\u003e\u003cp\u003eFragrance A (Floral \u0026amp; Fruity) also demonstrated a notable increase in alpha activity (mean difference\u0026thinsp;=\u0026thinsp;+\u0026thinsp;4.1523 \u0026micro;V\u0026sup2;/Hz) with a p-value at the threshold of significance (p\u0026thinsp;=\u0026thinsp;0.032), indicating a possible calming response. However, the decrease in theta power (\u0026minus;\u0026thinsp;4.0673 \u0026micro;V\u0026sup2;/Hz, p\u0026thinsp;=\u0026thinsp;0.078) was not statistically significant, suggesting that the effect was primarily localized to the alpha frequency band.\u003c/p\u003e\u003cp\u003eIn contrast, Fragrance C (Citrus-Floral) did not yield statistically meaningful changes in either frequency band. Although minor shifts were observed, an increase in alpha and a decrease in theta with the respective p-values (0.145 and 0.353) indicate non-significant changes, implying minimal or inconsistent effects on cortical relaxation.\u003c/p\u003e\u003cp\u003eAs expected, the placebo group exhibited no significant changes in alpha (p\u0026thinsp;=\u0026thinsp;0.994) or theta power (p\u0026thinsp;=\u0026thinsp;0.592). These results help validate the reliability of the findings in the experimental groups and minimize the influence of confounding factors.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.4 Topographical Distribution of Alpha and Theta Band Power\u003c/h2\u003e\u003cp\u003eFollowing the statistical analysis, topographical maps were generated to visually represent the spatial distribution of alpha and theta power across the scalp. These maps further illustrate the EEG changes observed after fragrance exposure and confirm the alterations in cortical activity patterns.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e7\u003c/span\u003e displays the distribution of alpha activity across the scalp for each condition, both before and after fragrance exposure. An increase in alpha power is visually observable, particularly following exposure to Fragrance B, indicating a pronounced calming effect. Fragrance A and Fragrance C also showed moderate increases in alpha power, while the placebo condition demonstrated minimal visual change.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e8\u003c/span\u003e illustrates the theta band distribution, where a general decrease in theta power was observed following fragrance exposure. The most notable reductions occurred under Fragrance A and Fragrance C, suggesting reduced drowsiness or mental disengagement (Daneshgar et al., 2025). In contrast, Fragrance B showed minimal theta change, indicating a calming effect without inducing drowsiness (Bonakdarpour et al., 2023). The placebo condition again showed no meaningful differences across the scalp. Overall, spatial visualization supports the quantitative EEG findings, showing that fragrance exposure, particularly Fragrance B, elicited measurable changes in cortical activity associated with calmness and alert relaxation.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4 Discussion","content":"\u003cp\u003e\u003cb\u003eA. Effects of Fragrance A (Floral\u0026ndash;Fruity) on EEG Alpha and Theta Activity\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe EEG results showed that Fragrance A (Floral\u0026ndash;Fruity) was associated with a significant increase in alpha power and a reduction in theta power from pre- to post-exposure. This pattern is consistent with previous findings, where enhanced alpha activity is linked to relaxed wakefulness and internalized attention (Deshmukh, 2023). The olfactory characteristics of Fragrance A, which combine floral and fruity notes, may evoke emotional comfort or mood stabilization through the engagement of limbic\u0026ndash;cortical pathways involved in affective regulation. The increase in alpha activity suggests that this fragrance profile contributes to a sense of calmness or relaxed alertness, although additional comparisons across scent categories would be necessary to determine its distinctiveness.\u003c/p\u003e\u003cp\u003e\u003cb\u003eB. Effects of Fragrance B (Spices \u0026amp; Wood) on EEG Alpha and Theta Activity\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFragrance B (Spices \u0026amp; Wood) elicited the most prominent neural effect among all conditions, producing a significant increase in alpha power (p\u0026thinsp;=\u0026thinsp;0.008) without a corresponding change in theta activity (p\u0026thinsp;=\u0026thinsp;0.966). This EEG profile indicates enhanced cortical relaxation while maintaining mental alertness, a combination typically associated with calm attention. The olfactory profile of Fragrance B includes woody and resinous compounds such as Cedrol and Thujopsene, both of which have been reported to exhibit sedative and anxiolytic properties (Maduka et al., 2024). These findings provide electrophysiological evidence that complex fragrances containing these compounds can modulate brain activity linked to calmness. Further studies incorporating chemical composition analyses and cross-condition comparisons could clarify whether this effect is unique to woody\u0026ndash;spice fragrances or generalizable to other calming scents.\u003c/p\u003e\u003cp\u003e\u003cb\u003eC. Effects of Fragrance C (Citrus\u0026ndash;Floral) on EEG Alpha and Theta Activity\u003c/b\u003e\u003c/p\u003e\u003cp\u003eExposure to Fragrance C (Citrus\u0026ndash;Floral) resulted in minor, non-significant increases in alpha power and slight reductions in theta power. This limited EEG response suggests that this fragrance type may induce a more alert or invigorating state rather than a calm one. Previous studies have indicated that citrus-based scents such as limonene and linalool can enhance arousal and attentional readiness (Eissa, 2024). Thus, the weaker modulation of alpha and theta activity observed here may reflect the stimulating properties of citrus\u0026ndash;floral compositions, aligning with their common association with freshness and mental alertness rather than relaxation.\u003c/p\u003e\u003cp\u003e\u003cb\u003eD. Effects of Placebo on EEG Alpha and Theta Activity\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe placebo condition displayed no statistically significant changes in alpha (p\u0026thinsp;=\u0026thinsp;0.994) or theta power (p\u0026thinsp;=\u0026thinsp;0.592), confirming that the EEG variations observed in the fragrance groups were attributable to olfactory stimulation rather than experimental artifacts or time-dependent effects. The stability of neural activity in the placebo group supports the reliability of the experimental design and validates the role of the fragrances as the primary modulators of EEG responses. The absence of significant cortical changes under this condition emphasizes the functional importance of olfactory input in eliciting measurable neurophysiological effects, distinguishing true sensory-driven modulation from baseline neural variability.\u003c/p\u003e"},{"header":"5 Conclusion","content":"\u003cp\u003e This study explored the neurophysiological effects of commercial fragrances on EEG activity in healthy male participants. Power density analysis revealed that Fragrance B (Spices \u0026amp; Wood) produced the largest increase in alpha power (+\u0026thinsp;5.34 \u0026micro;V\u0026sup2;/Hz) accompanied by a slight decrease in theta power (\u0026minus;\u0026thinsp;0.06 \u0026micro;V\u0026sup2;/Hz), suggesting enhanced cortical calmness without drowsiness. Fragrance A (Floral\u0026ndash;Fruity) also increased alpha power (+\u0026thinsp;4.15 \u0026micro;V\u0026sup2;/Hz) and decreased theta power (\u0026minus;\u0026thinsp;4.06 \u0026micro;V\u0026sup2;/Hz), indicating a moderate relaxation response. In contrast, Fragrance C (Citrus\u0026ndash;Floral) produced smaller changes in alpha (+\u0026thinsp;1.19 \u0026micro;V\u0026sup2;/Hz) and theta (\u0026minus;\u0026thinsp;2.95 \u0026micro;V\u0026sup2;/Hz), while the placebo showed no significant EEG variations. Overall, these findings provide objective electrophysiological evidence that changes in alpha power may serve as a reliable neural indicator of calmness following fragrance exposure.\u003c/p\u003e\u003cp\u003eThe present study contributes to understanding how distinct olfactory compounds interact with cortical networks involved in emotional and attentional control. Future research could expand on these results by including female participants, employing larger sample sizes, and examining the long-term or cross-modal effects of fragrance exposure on neural oscillatory dynamics.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors extend their sincere gratitude to the Faculty of Science and Technology, Universiti Sains Islam Malaysia (USIM), the Brain \u0026amp; Behaviours Research Group (BBRG), and Sugarbomb Sdn. Bhd. for their invaluable support and collaboration throughout this research.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was supported by the USIM Research Grant (PPPI/BM/FST/USIM/113823).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that there are no conflicts of interest regarding the publication of this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was conducted in accordance with the principles of the Declaration of Helsinki and was approved by the Ethical Committee USM (USM/JEPeM/KK/24121070).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAhmad, S., \u0026amp; Pratap, P. D. (2024). Unravelling the Environment, Aroma, and Molecular Effects on Mood Fluctuations: A Review. 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Emotion, motivation, decision-making, the orbitofrontal cortex, anterior cingulate cortex, and the amygdala. \u003cem\u003eBrain Structure and Function\u003c/em\u003e, \u003cem\u003e228\u003c/em\u003e(5), 1201-1257. https://doi.org/10.1007/s00429-023-02644-9.\u003c/li\u003e\n\u003cli\u003eSowndhararajan, K., \u0026amp; Kim, S. (2016). Influence of fragrances on human psychophysiological activity: With special reference to human electroencephalographic response. Scientia pharmaceutica, 84(4), 724-752. https://doi.org/10.3390/scipharm84040724.\u003c/li\u003e\n\u003cli\u003eWorld Medical Association. (2025). World Medical Association Declaration of Helsinki: ethical principles for medical research involving human participants. Jama, 333(1), 71-74. doi:10.1001/jama.2024.21972.\u003c/li\u003e\n\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":"Electroencephalography (EEG), Brain Waves, Fragrance, Calmness, Olfactory","lastPublishedDoi":"10.21203/rs.3.rs-8073748/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8073748/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eFragrance exposure can influence emotional and cognitive processing by modulating cortical oscillations linked to calmness and internal attention. This study investigates electroencephalographic (EEG) changes in alpha (8\u0026ndash;13 Hz) and theta (4\u0026ndash;8 Hz) power density following exposure to different fragrance conditions among healthy male participants. EEG signals were recorded using the Unicorn Hybrid 8-channel system at frontal (Fz), parietal (Pz), and parieto-occipital (PO7, PO8) sites before and after controlled fragrance exposure. Power-spectral analysis was conducted to quantify changes in alpha and theta activity associated with calm emotional states. The results revealed differential modulation of alpha and theta power density across cortical regions following fragrance exposure, suggesting that specific olfactory inputs can alter neural oscillations indicative of calmness. These findings provide electrophysiological evidence for the neural basis of fragrance-induced calmness and contribute to the broader understanding of olfactory\u0026ndash;cortical interactions in emotion regulation.\u003c/p\u003e","manuscriptTitle":"EEG Alpha and Theta Power Modulation During Fragrance Exposure: Insights into the Neural Correlates of Calmness","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-11-24 10:27:24","doi":"10.21203/rs.3.rs-8073748/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":"37636c19-9773-4078-94e6-bba1cf46d5dd","owner":[],"postedDate":"November 24th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-24T00:23:30+00:00","versionOfRecord":[],"versionCreatedAt":"2025-11-24 10:27:24","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8073748","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8073748","identity":"rs-8073748","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}