Psychophysiology

The P300 event-related potential is one of the most studied electrophysiological markers of cognition, yet trial-to-trial variability within conditions has traditionally been treated as measurement error.The vP300 framework proposes that P300 variability, quantified by the coefficient of variation (CV), may reflect locus coeruleus-norepinephrine (LC-NE) mode dynamics. A computational simulation (N = 80) tested three hypotheses. Empirical P3 oddball data from the ERP CORE dataset (N = 39) provided partial validation. Mean amplitude and CV were orthogonal in simulation (r = -0.14, n.s.) and moderately correlated in empirical data (r = -0.418, p = .008), with 82.5% of CV variance independent of mean amplitude. CV significantly predicted cognitive flexibility (r = -0.319, p = .004) while mean amplitude did not (r = .010, p = .928). Trial- to-trial P300 variability carries information orthogonal to traditional mean amplitude, supporting a potential revision of how variability is treated in ERP research.

Intelligence or general cognitive ability (GCA) is fundamental to human behavior and cognition. It impacts important life outcomes like educational success and even health and longevity have been related to differences in GCA. Understanding the biological basis of such individual variations presents a crucial goal of neuroscience. The mismatch negativity (MMN) is an event-related brain potential that can be measured when--within a series of frequent standard stimuli, rare deviants are presented--and is suggested to reflect conscious (active) or unconscious (passive) detection processes of the brain. Importantly, variations in MMN amplitude and latency have been linked to differences in GCA. Yet findings vary considerably. This preregistered meta-analysis provides a comprehensive and structured overview of the current state of research. Following the study selection process in accordance with the PRISMA guidelines, and the rating of study design quality with the Study Design and Implementation Assessment Device for Individual Difference Research (DIAD-ID), the association between GCA and MMN amplitude and latency was examined in 695 healthy adults across 13 included studies. The estimated across-sample associations between MMN and GCA were small, but significant (MMN amplitude-GCA: r = -0.08, MMN latency-GCA: r = -0.13; p < 0.05) and moderators were identified. Between-sample heterogeneity was moderate, with no evidence of publication bias. Our findings suggest that higher cognitive ability is associated with slightly stronger and faster MMN responses. However, the low estimated across-sample effect sizes and the small number of included studies also highlight the need for more research.

The olfactory and intranasal trigeminal systems interact closely, influencing chemosensory perception, yet the mechanisms underlying their interaction remain poorly understood and have been studied mainly in young adults. We aimed to characterize olfactory-trigeminal interactions in aging by comparing electrophysiological and behavioral responses under ipsilateral and contralateral olfactory-trigeminal co-stimulation, to determine the relative contributions of peripheral and central mechanisms. Using chemosensory event-related potentials and a localization task, 44 healthy older adults (66.3 {+/-} 4.6 years; 29 women) were tested under four conditions: pure trigeminal (carbon dioxide; CO2), pure olfactory (2-phenylethanol; PEA), ipsilateral co-stimulation (PEA+CO2 in the same nostril), and contralateral co-stimulation (PEA+CO2 in opposite nostrils). Ipsilateral, but not contralateral olfactory-trigeminal co-stimulation, improved trigeminal localization performance and induced larger late positive component amplitudes. Together, these findings suggest that olfactory-trigeminal interactions are driven primarily by peripheral rather than central mechanisms. This study also provides normative CSERP data for healthy older adults.

Creative performance fluctuates from moment to moment, suggesting that it depends partly on transient internal states present before creative thinking begins. Although such fluctuations have been identified in central neural activity, it remains unclear whether they are also reflected in autonomic physiology. We examined whether cardiac and electrodermal activity during a brief pre-trial resting period was associated with subsequent creative performance. Photoplethysmography, electrocardiography, and electrodermal activity were recorded while 28 participants completed the Alternative Uses Test and Fusion Innovation Test, assessing divergent and convergent creative thinking, respectively. Data from 27 participants was included in the analyses. Heart rate, heart rate variability, tonic skin conductance level, and phasic skin conductance activity were extracted from observation windows ranging from 11 to 30 s within a 30-s pre-trial rest period. Trial-level creativity was evaluated using GPT-based ratings of novelty, feasibility, and goal attainment. Linear mixed-effects models showed that higher pre-trial tonic skin conductance level was consistently associated with better subsequent creative performance across tasks, with overall model fit peaking at a 21-s observation window. Permutation-based feature-importance analysis provided convergent support for the contribution of tonic skin conductance, whereas the cardiac and phasic electrodermal indicators showed no reliable independent associations. However, the model explained only a small proportion of behavioral variance. These findings suggest that tonic sympathetic arousal reflects a momentary physiological state associated with creativity potential, while autonomic signals alone remain insufficient for accurate individual-level prediction.

Human long-term memory for visual scenes is remarkably robust, yet the neural mechanisms supporting memory encoding and retrieval remain poorly understood when both processes must operate at the same time. For instance, this might happen when we encounter a familiar place while simultaneously forming new memories of this encounter. We investigated electrophysiological correlates of visual recognition memory using a continuous recognition task (CRT), in which participants judged a continuous stream of scene photographs as previously seen or new, such that encoding and retrieval occurred in parallel on every trial. To make recognition particularly demanding, stimuli were drawn from only four scene categories. Thirty-one participants performed the task while EEG was recorded, and we analyzed canonical ERP markers of retrieval (mid-frontal FN400, 300-550 ms; late parietal effect, LPE, 550-800 ms) and encoding (subsequent memory effect, SME) as a function of stimulus repetition and lag between consecutive presentations. FN400 showed robust old/new effects for both repetitions, whereas LPE differences emerged only at the second repetition. While FN400 amplitude was insensitive to lag, LPE amplitude decreased systematically with increasing lag, mirroring the behavioral pattern of declining accuracy and slower responses. A significant SME emerged selectively for images subsequently recognized on both repetitions, indicating that the SME in continuous recognition is specific for the most robustly encoded items and reflects the strength of encoding. Together, these findings show that canonical ERP markers of recognition memory are preserved even when encoding and retrieval operate concurrently, but their expression depends on how often and how recently an item has previously been encoded - parameters that can be flexibly manipulated within the CRT. This demonstrates that the CRT is sensitive to fine-grained temporal dynamics of memory formation and retrieval that could be missed under standard single-repetition designs.

The gastrics intrinsic slow-wave rhythm couples to ongoing cortical activity in humans, but the functional significance of this gastric-brain coupling remains poorly understood. Using simultaneous electroencephalography and electrogastrography, we examined how gastric-brain coupling changes during a mental task and subsequent recovery and whether these dynamics relate to autonomic responses in healthy adults (HA) and individuals with Irritable Bowel Syndrome (IBS), a disorder of gut-brain interactions. In HA, gastric-brain coupling decreased during mental task and gradually returned to baseline during recovery, primarily for cortical alpha rhythms. Greater reductions in gastric-brain coupling were associated with stronger sympathetic arousal, indicating that gastric-brain coupling is associated with physiological responses to cognitive demand. In IBS, gastric-brain coupling dynamics were preserved. However, unlike HA, sympathetic arousal was not associated with gastric-brain coupling reductions, suggesting an alteration in the functional relationship between gastric-brain coupling and autonomic regulation despite preserved coupling dynamics. Further, in HA, greater reductions in gastric-brain coupling were associated with higher anxiety and neuroticism and lower interoceptive awareness. In contrast, these relationships were reversed in IBS, with greater gastric-brain coupling dynamics observed in individuals with higher anxiety and neuroticism and lower interoceptive awareness. Together, gastric-brain coupling emerges as a dynamic physiological process associated with autonomic responses to cognitive demand. In IBS, these dynamics are preserved but their physiological and psychological associations are altered, indicating a dissociation between gastric-brain coupling and its functional correlates. Significance StatementThe functional role of gastric-brain coupling remains largely unknown. We show that coupling between the gastrics intrinsic slow-wave rhythm and cortical activity is dynamically reduced during mental engagement and recovers afterward, primarily through alpha rhythms. In healthy adults, these changes follow sympathetic arousal, linking gastric-brain coupling to autonomic responses to cognitive demands. In irritable bowel syndrome, coupling dynamics remain intact but lose their relationship with autonomic responses and show altered associations with anxiety, neuroticism, and interoceptive awareness. These findings suggest that gastric-brain coupling contributes to the physiological organization of brain-body states and that irritable bowel syndrome may involve altered functional interpretation of visceral signals despite preserved gastric-brain coupling dynamics.

Aperiodic neural activity (1/f EEG) has been proposed to reflect the balance between excitatory and inhibitory (E/I) inputs, with steeper spectral slopes reflecting increased inhibition and flatter slopes indicating excitation. This activity is also thought to reflect the temporal coordination of neural firing, offering insights into fundamental brain dynamics. Recent studies have shown that the 1/f slope is sensitive to stimulus onset, characterized by initial inhibitory shifts followed by excitatory rebounds, which may reflect cognitive control mechanisms involved in suppressing distractions and preparing goal-directed responses. However, previous research has relied on fixed temporal windows and insufficient control of ERP contamination, limiting our understanding of rapid control dynamics. Here we used newly developed time-resolved analyses to study 1/f spectral slope modulation during a Picture-Word Interference task, focusing on two canonical cognitive control markers: the Congruency Effect (CE) and Congruency Sequence Effect (CSE). Forty-nine participants categorized pictures while ignoring congruent or incongruent words. Behaviorally, we replicated robust CE and CSE patterns. Spectral slope analyses showed that incongruent trials elicited steeper slopes -- consistent with increased inhibition -- particularly in frontal and central regions, reflecting conflict-related control engagement. Moreover, CSE analyses revealed dynamic slope modulations across frontal, central, and occipital components over time, suggesting control adjustments influenced by previous trial congruency. These results provide the first within-trial time-resolved evidence that aperiodic 1/f EEG activity can track both immediate conflict resolution and cognitive adjustments, offering a temporally sensitive neural marker of cognitive control, albeit with effects that are small in magnitude on average.

Cardiovascular regulation depends on bidirectional communication between autonomic cardiac control and cardiac afferent signals ascending to the central nervous system, forming a heart-brain loop. Cardio-auditory omission paradigms provide a non-invasive way to probe this loop in humans by withholding scheduled tones within heartbeat-contingent auditory sequences and measuring the resulting autonomic cardiac and heartbeat-related cortical responses. Previous studies have shown omission-evoked cardiac deceleration and neural responses mainly in specific contexts such as passive listening or synchrony-judgement tasks. The present study examined whether these responses also occur under the more general condition of active responses to external stimuli. We tested 40 adults in an auditory detection task in which tones were presented either 200 ms after the ECG R-peak (synch) or at pseudo-random intervals matched to each participants resting heart rate (asynch). A five-minute no-stimulation resting recording was used to generate the asynch sequence and served as the resting comparison condition. In both auditory conditions, 10% of scheduled tones were omitted, yielding synch and asynch omissions. Heartbeat-synchronous omissions induced sustained RR-interval prolongation that exceeded responses to asynch omissions, sound-present conditions, and rest. HEP amplitude was selectively enhanced in the synch-omission condition relative to all other conditions. Reaction times to the first post-omission tone were slightly delayed, whereas overall performance remained comparable across conditions. These findings show that heartbeat-synchronous auditory omissions produce a distinct autonomic-cortical response profile under active response demands, indicating that heart-brain loop dynamics continue to shape physiological responses during ongoing behaviour.

Immersive virtual reality (VR) can preserve the logic of laboratory attention tasks while altering the perceptual-action context in which attentional control is expressed. In this study, we examined the neural underpinnings of location-response compatibility in a VR adaptation of the Attention Network Test-Revised (ANT-VR), using a restricted preprocessing multiverse to account for uncertainty arising from defensible EEG analysis choices. Forty-four young adults contributed complete ANT-VR behavioural data. Target-locked EEG analyses were conducted across 192 preprocessing branches, with branch-level participant contributions varying after quality check and trial-count filtering. The contrast compared location-response incompatible with compatible trials and was balanced within participants across cue-target interval, cue condition, flanker congruency, and, for spatial-cue trials, conditions in which spatial cues were valid or invalid for subsequent targets. Across the multiverse, the N2pc-window posterior-lateralisation contrast could be defined in all branches and showed high directional stability: the median incompatible-minus-compatible effect was 0.30 uV [IQR: 0.22 to 0.41], with positive effects in 192/192 branches, nominal evidence in 79/192 branches, and Holm-corrected evidence in 42/192 branches. Comparison across ERP measures indicated that this pattern was more consistent for N2pc-window posterior lateralisation than for P1, posterior N1, frontocentral N2, P3, or response-referenced C3/C4 measures. Comparison across C3/C4 reference frames further constrained the interpretation: target-location-referenced C3/C4 showed the strongest effect, whereas response-referenced C3/C4 was weaker. Behavioural analyses showed no reliable compatibility differences. These findings suggest that location-response compatibility in immersive ANT-VR modulates target-locked lateralised neural activity associated with spatial selection and target-location coding, rather than producing broad sensory, conflict-related, P3-related, or specifically response-referenced modulation.

Spontaneous thought changes over time, yet the moment-to-moment factors shaping these changes remain poorly understood. We examined whether heartbeat-related bodily processing, operating largely outside explicit awareness, is associated with the organization of ongoing thought. Forty adults performed an auditory attention task with intermittent thought probes in which auditory events were scheduled either 200 ms after each detected R peak (synch condition) or independently of ongoing cardiac timing (asynch condition), with occasional omissions in both conditions. Heartbeat-synchronous omissions in this paradigm have been shown to induce cardiac deceleration and modulate heartbeat-evoked potentials (HEPs). The score of the heartbeat counting task (HCT) served as a behavioral index related to cardiac interoceptive accuracy. The results showed that higher HCT score was associated with a stronger synch-asynch shift toward more self-related and less task/self-unrelated thought. HEPs showed a synch-related negative shift across several thought groups, although the magnitude of this condition effect did not reliably differ among thought groups. Overall thought-group distributions were similar across conditions, while transition analyses suggested a tendency in the synch condition toward more frequent transitions linking predominantly interoceptive stimulus-dependent thought with both on-task and self-related thought. Together, these findings suggest that heartbeat-related bodily processing may influence the organization of spontaneous thought, particularly in individuals with greater cardiac interoceptive accuracy. Bodily signals may therefore act as an automatic constraint on the ongoing stream of thought, biasing which thought contents and transitions become more likely over time.

Each day we make dozens of decisions about food. These choices are informed not only by information that we receive from our senses, but also by our memories, values, cultural norms, and goals. Evidence accumulation models have been proposed to explain how we transform these disparate sources of information into dietary choices and their corresponding motor actions. These models describe decisions arising from a noisy integration of decisional evidence until a criterion is reached. We investigated whether the centroparietal positivity (CPP), an event-related potential component proposed as a neural correlate of evidence accumulation during perceptual judgements, also traces accumulation trajectories during dietary decisions. Participants (N = 110) made speeded Yes/No judgements about food images relating to three attributes (healthiness, tastiness, and willingness to eat) while electroencephalography was recorded. They subsequently provided continuous ratings for each attribute. After applying signal deconvolution techniques, CPP waveforms exhibited a close correspondence to hypothesised evidence accumulation trajectories, showing steeper amplitude build-up rates for both faster decisions and continuous ratings more strongly in favour of one's categorical choice. Our findings provide clear support for a neurally instantiated evidence accumulation process that integrates multiple sources of information to produce dietary decisions.

Digital behaviour change interventions have emerged as a promising approach for improving health, well-being, and performance, yet relatively few studies have evaluated their effects using objective biological and neurophysiological measures. The present study examined the effectiveness of Autonomic, a neuroscience-informed digital coaching platform designed to improve student well-being through personalized behavioural interventions targeting sleep, stress, mood, energy, and focus. Thirty university students engaged with the platform for ten weeks and completed behavioural assessments, biomarker collection, and electroencephalographic (EEG) testing at baseline, five weeks, and ten weeks. Behavioural outcomes included self-reported ratings of focus, energy, sleep, mood, and stress. Biological measures included salivary cortisol and tear fluid dopamine concentrations. EEG assessments included resting-state recordings, frontal theta activity during a working memory task, and N200/P300 event-related potentials during a visual oddball task. Significant improvements were observed in self-reported focus, energy, and sleep quality across the intervention. Electrophysiological measures demonstrated reduced frontal theta power during working memory and shorter P300 latencies during attentional processing, consistent with more efficient cognitive processing following the intervention. Although cortisol, dopamine, and resting-state EEG measures did not reach statistical significance, all exhibited changes in the predicted direction. Collectively, these findings provide converging behavioural, biological, and neurophysiological evidence supporting the effectiveness of Autonomic. More broadly, the study demonstrates the value of combining objective biomarkers and EEG with traditional behavioural assessments when evaluating digital behaviour change interventions and highlights the potential of neuroscience-informed coaching platforms to improve health, well-being, and cognitive functioning in university students.

While extensive research has been conducted on emotion recognition from facial stimuli, it remains unclear how embodied emotional cues conveyed through body postures, gestures and actions (e.g., stick figures) compare with facial (human faces) and face-like symbolic representations (emoji faces) in shaping behavioral and neural responses. We employed a multimodal approach, combining behavioral measures (accuracy and reaction time) with electroencephalography (EEG) to examine the electrophysiological correlates of emotion recognition. Overall, sixty-six (equal number of males and females; 18-30 year old) participants identified positive, negative, and neutral emotions depicted in the three formats. Behavioral results showed significant effects of both emotion and format on accuracy and reaction time. Emoji faces were recognized with the highest accuracy and fastest reaction times, followed by stick figures and then human faces (p < .001, some comparisons p < .05). Thirty-four participants (17 males and 17 females) underwent EEG, which revealed distinct patterns of event-related potentials (ERPs). The Early Posterior Negativity (EPN) amplitude showed a significant overall effect of format. Post-hoc comparisons indicated that stick figures elicited greater (more negative) EPN amplitudes than human faces during positive emotion recognition (p = .003), and greater amplitudes than both emoji faces (p = .027) and human faces (p = .007) during negative emotion recognition. No significant differences were observed between emoji and human faces. N170 and Late Positive Potential (LPP) amplitudes did not reveal significant differences (all p > .05). Correlation analyses revealed no significant associations between ERP and behavioral measures. Thus, abstract, minimalistic representations like stick figures elicit enhanced early emotion-related processing despite similar early and later processing across formats. HighlightsO_LIEmotion recognition across realistic (human faces), symbolic (emoji faces) and embodied (stick figures) modalities were compared. C_LIO_LIEmotions were recognized fastest and most accurately in emoji faces format. C_LIO_LIStick figures format elicited significantly higher EPN compared to other two formats across positive and negative emotions. C_LIO_LINo significant differences were observed in terms of N170 and LPP. C_LIO_LIEmbodied, abstract emotional cues modulate automatic emotional appraisal, rather than initial sensory encoding and sustained cognitive evaluation. C_LI

The vestibular system has been implicated in several aspects of self-representation, including bodily self-location, yet its role in episodic source and reality monitoring remains unclear. Moreover, symptoms of depersonalisation and derealisation (DPDR) have been associated with both vestibular dysfunction and altered source and reality monitoring. We tested whether noisy galvanic vestibular stimulation (nGVS) modulates source and reality monitoring during a word-encoding paradigm and whether this increased symptoms of DPDR. Sixty young adults (N = 30 active nGVS, N = 30 sham) encoded words that varied by context (spoken vs. imagined), agentic source (self vs. other), and valence (positive vs. threat) before completing source/reality judgments. Active nGVS reduced overall accuracy relative to sham on both reality and source monitoring. Across conditions, self-referential items were remembered with greater sensitivity compared to other-referential items, and spoken items were recalled with greater sensitivity than imagined items. We additionally show an interaction effect whereby active nGVS reduced accuracy specifically for imagined and threat-valenced items. Trait DPDR did not moderate the effects of stimulation, although higher trait DPDR was associated with a more liberal reality-monitoring response criterion. Results indicate that transient vestibular perturbation via nGVS can impair source monitoring for internalised and threatening stimuli and impairs cognitive distinctions between internally and externally generated events in general, supporting a role for vestibular input in maintaining self-other and reality boundaries in episodic memory.

Eye blinks are among the largest physiological artefacts in electroencephalography and are typically removed from neural recordings. Yet their timing may carry information about cognition. Here, we asked whether the temporal distribution of spontaneous blinks across trials provides a time-resolved behavioural signature of internal attentional focusing in working memory. In Experiment 1, blink-locked EEG analyses showed that blink timing was aligned with neural activity reflecting attentional focusing on a relevant internal representation. In Experiment 2, participants remembered the same visual information across conditions, but the relevant item was revealed either early, by a cue before report, or later, at report. Blink-frequency profiles shifted accordingly, increasing after the cue when selection was possible early and after the probe when selection was delayed. Post-cue blinks in the early-selection condition were also associated with better memory performance. Thus, more generally, spontaneous blinks provide an unobtrusive chronometric signal for tracking latent cognitive processing.

Pupil dilation offers a sensitive, non-invasive window into the neurocognitive processes supporting human associative learning. Yet, the field lacks consensus on how to quantify conditioned pupil responses, particularly which time intervals best serve as readouts. Moreover, it remains unresolved whether pupil dilation during learning reflects a unitary arousal signal or multiple (overlapping yet distinct) processes that unfold sequentially (e.g., cue valuation, uncertainty-driven attention, anticipation, prediction-error [PE] signaling). To address this, we conducted a large-scale individual-participant-data reanalysis (mega-analysis) of harmonized primary studies from our lab (K = 7 independent samples; total N = 385; 562 sessions), reprocessed through an identical pipeline, with systematic variation in outcome valence and modality. Temporal PCA of CS- and US-locked epochs yielded highly stable component structures across trials and studies, which carried dissociable information: An early (CS-locked) component selectively tracked appetitive value, distinguishing reward cues before aversive differentiation emerged. Later phases reflected differential conditioning across both valences, increasingly coupled to arousal toward US onset. Aversive learning was most specifically expressed in responses peaking around expected US delivery, which also predicted negative valence ratings. Two subsequent components captured unconditioned responding and its modulation by unexpected outcomes and omissions, consistent with unsigned PE signaling (amplified after aversive cues) and, later, positive PEs. Generalized additive mixed models largely converged with the PCA structure. Pupil dilation is therefore not a unitary marker of conditioning, but rather a high-resolution readout of sequential processes such as valuation, arousal/attention, and outcome updating, offering a promising framework for future computational models of learning.

Emotions are dynamic experiences that unfold over time, yet most affective neuroscience studies have relied on static stimuli and laboratory-based EEG systems. This study examined whether emotional valence and arousal can be reliably decoded using a consumer-grade wearable EEG device in naturalistic contexts. Forty-three participants viewed video clips designed to elicit four core affect categories including high-arousal positive, low-arousal positive, high-arousal negative, and low-arousal negative, while EEG signals were continuously recorded. Multivariate analyses, including classification, multidimensional scaling (MDS), and intersubject correlation (ISC), were employed to assess affective representation and neural synchrony. Behavioral data demonstrated robust classification of both valence and arousal, whereas EEG data yielded consistent above-chance classification of valence but less stable decoding of arousal, particularly in within-participant analyses. MDS revealed that both behavioral and EEG responses were primarily organized along the valence dimension, with weaker separation along arousal. ISC analyses further indicated frequency- and region-specific neural synchrony, with stronger alignment in left and temporal electrodes, though overall ISC values were modest, likely reflecting the brief duration of stimuli. Taken together, these findings suggest that valence is more stably represented in both subjective and neural domains, whereas arousal may require time-resolved or longer-duration approaches for reliable decoding. This work demonstrates the feasibility and limitations of employing wearable EEG for theory-driven affective neuroscience, underscoring its potential for scalable and ecologically valid emotion research beyond laboratory settings.

Menstrual symptoms vary across the cycle, yet most research assumes a normative 28-day cycle with fixed phase durations, obscuring the physiological relevance of natural cycle variation. Using the mcPHASES dataset, we characterised cycle and phase length variation across 96 menstrual cycles from 37 participants, with ovulation timing estimated from daily urinary luteinizing hormone measurements using a Bayesian hierarchical model, and examined associations with daily symptoms in a subset of 64 cycles from 35 participants with complete symptom data. Twelve physical, mental, and behavioural symptom domains were modelled using Bayesian ordinal regression, with posterior uncertainty in phase-length predictors propagated via a measurement error framework. Total cycle length was not associated with daily symptom burden, except sleep disturbances. By contrast, phase length decomposition revealed systematic associations across multiple domains: longer menstrual phase length was broadly associated with greater symptom intensity spanning physical, gastrointestinal, affective, and sleep domains; longer luteal phase duration was associated with greater fatigue and more frequent headaches, but lower sore breast intensity and lower stress; and longer follicular phase duration and later ovulation were each associated with greater sore breast intensity and more frequent mood swings. These associations require knowledge of actual ovulation timing and cannot be recovered from cycle length alone, indicating that the common assumption of a fixed 14-day luteal phase introduces systematic misclassification of hormonal exposure. Daily symptom intensity was also predominantly person-specific, with cycle phase explaining little of the between-person variance across most symptoms. These findings indicate that calendar-based phase assignment is insufficient for research and clinical assessment of hormone-sensitive conditions, and that person-specific baselines, rather than population-level phase averages, are needed for clinically meaningful symptom monitoring.

Gut-brain communication has emerged as a rapidly expanding field of research, with recent electrophysiological studies revealing rhythmic gut-brain coupling between gastric activity and brain oscillations in humans. Gut motility is a key determinant of gastrointestinal function, but it remains unclear whether individual differences in gut motility reflected by weekly bowel movements (e.g., defecation frequency) are associated with differences in gut-brain coupling. Here, we address this question by examining women with self-reported daily bowel movements (N = 38) and women with less frequent bowel movements (N = 38). We recorded simultaneous electroencephalography (EEG) and electrogastrography (EGG) at fasting state, performed cognitive assessments, and analysed faecal short-chain fatty acids (SCFAs) as markers of colonic fermentation. In a subset of participants, EEG-EGG coupling was assessed twice over an interval of at least eight weeks to assess test-retest reliability. In this group, EEG-EGG coupling showed moderate test-retest reliability (Intraclass Correlation Coefficient (ICC) = 0.50). When comparing the two groups of women, the phase-amplitude coupling (PAC) analysis between EEG and EGG signals revealed a significantly stronger gut-brain coupling in women with daily bowel movements compared to women with less frequent bowel movements (p = 0.03). We additionally found that women with daily bowel movements made less errors in the cognitive tasks and had higher levels of faecal SCFAs. A path analysis suggested that bowel movements significantly affect gut-brain phase-amplitude coupling through faecal SCFAs. However, neither faecal SCFAs nor phase-amplitude coupling significantly predicted cognitive performance, suggesting the existence of alternative pathways for the association between bowel movements and cognitive performance. Together, our findings suggest that the strength of gut-brain coupling is associated with bowel movements and cognitive performance, making EEG-EGG coupling a promising marker of human gut-brain interactions.

BackgroundThe maturation of the autonomic nervous system (ANS) has been suggested to play a crucial role in the development of emotion regulation and later psychosocial functioning. However, longitudinal evidence linking early autonomic development to long-term outcomes remains limited. This longitudinal study investigated the interplay between birth-related factors, early autonomic activity, and psychosocial outcomes across development. MethodsThe sample comprised 101 participants followed from two weeks to 14 years of age, with heart rate (HR) and vagally ediated heart rate variability (vmHRV) assessed at 2 weeks, 6 weeks, 3 months, 14 months, and 14 years. Linear models were used to examine associations between birth-related factors and early HR and vmHRV, as well as whether HR and vmHRV trajectories during the first 14 months predicted psychosocial outcomes at 5 and 14 years. ResultsMultiple birth-related factors significantly predicted HR and vmHRV at two weeks after birth. Moreover, flatter age-related increases in vmHRV and weaker decreases in HR during infancy predicted higher maternally reported psychosocial difficulties at 14 years in males only, with no such effects at 5 years or in females. ConclusionsThese findings underscore the importance of early autonomic maturation in shaping later psychosocial functioning, with effects on adolescent outcomes observed in males only. Early ANS trajectories may represent meaningful predictors of neurodevelopmental outcomes, highlighting their potential relevance for early identification of later psychosocial risk in a sex-specific manner.