Shaping functional architecture by oscillatory alpha activity: gating by inhibition

An experimental EEG study of brain activities underlying the Autonomous Sensory Meridian Response

Autonomous Sensory Meridian Response (ASMR) is an audio-visual phenomenon that has recently become popular. Many people have reported experiencing a tingling-like sensation through their body while watching audio/video clips known as ASMR clips. People capable of having such experiences have also reported improved overall well-being and feeling relaxed. However, the neural activity underlying this phenomenon is not yet well-studied. The present study aims to investigate this issue using electroencephalography (EEG) employing an exploratory approach. We recorded resting-state EEGs from twelve participants before and after watching an ASMR clip and a control video clip. We divided the participants into two groups capable of experiencing ASMR tingling (ASMR group) and not capable of experiencing ASMR tingling (Non-ASMR group), by performing "Jenks Natural Breaks" clustering method on the results of a self-report questionnaire. We calculated the spectral power of EEG recording and compared the resulting values between the groups and sessions. We demonstrated a decline in the power of EEG activities in the delta frequency band in all regions of the brain and an increase in alpha activity in the occipital area of the brain and increases in beta oscillations was noted over the left fronto-temporal region of the brain among ASMR group. We did not observe similar results among the Non-ASMRs participants or among ASMRs in the control group.

Alpha transcranial alternating current stimulation modulates pain anticipation and perception in a context-dependent manner

ABSTRACT

Pain perception is closely tied to the brain's anticipatory processes, particularly involving the suppression of sensorimotor α-oscillations, which reflect the system's readiness for incoming pain. Higher sensorimotor α-oscillation levels are correlated with lower pain sensitivity. Alpha transcranial alternating current stimulation (α-tACS) can enhance these oscillations, potentially reducing pain perception, with effects that may be sustained and influenced by the certainty of pain expectations. Hence, this study investigated the immediate and sustained effects of α-tACS on pain anticipation and perception, focusing on how these effects are shaped by the certainty of expectations. In a double-blind, sham-controlled design, 80 healthy participants underwent a 20-minute session of real or sham α-tACS over the right sensorimotor region. Behavioral and neural responses related to pain anticipation and perception were recorded before, immediately after, and 30 minutes poststimulation under both certain and uncertain conditions. Compared with sham stimulation, real α-tACS disrupted the habituation of laser-evoked potentials (N2-P2 complex), particularly under certain expectations, with effects persisting 30 minutes poststimulation. In anticipatory brain oscillations, real α-tACS enhanced somatosensory α1-oscillations and increased midfrontal θ-oscillations in conditions of certainty, with θ-oscillation modulation showing sustained effects. Mediation analysis revealed that α-tACS reduced pain reactivity by enhancing somatosensory α1-oscillations but increased pain reactivity through the enhancement of midfrontal θ-oscillations, with the latter effect being more pronounced. These findings suggest that while α-tACS may provide pain relief through somatosensory α-oscillation augmentation, its stronger and longer-lasting impact on midfrontal θ-oscillations could lead to hyperalgesia, particularly in the context of certain pain expectations.

Reducing Tinnitus via Inhibitory Influence of the Sensorimotor System on Auditory Cortical Activity

Tinnitus is the subjective perception of a sound without corresponding external acoustic stimuli. Research highlights the influence of the sensorimotor system on tinnitus perception. Associated neuronal processes, however, are insufficiently understood, and it remains unclear how and at which hierarchical level the sensorimotor system interacts with the tinnitus-processing auditory system. We therefore asked 23 patients suffering from chronic tinnitus (11 males) to perform specific exercises, aimed at relaxing or tensing the jaw area, which temporarily modulated tinnitus perception. Associated neuronal processes were assessed using magnetencephalography. Results show that chronic tinnitus patients experienced their tinnitus as weaker and less annoying after completion of relaxing compared with tensing exercises. Furthermore, (1) sensorimotor alpha power and alpha-band connectivity directed from the somatosensory to the auditory cortex increased and (2) gamma power in the auditory cortex reduced, which (3) related to reduced tinnitus annoyance perception on a trial-by-trial basis in the relaxed state. No effects were revealed for 23 control participants without tinnitus (six males) performing the same experiment. We conclude that the increase in directed alpha-band connectivity from the somatosensory to the auditory cortex most likely reflects the transmission of inhibition from the somatosensory to the auditory cortex during relaxation, where concurrently tinnitus-related gamma power reduces. We suggest that revealed neuronal processes are transferable to other tinnitus-modulating systems beyond the sensorimotor one that is involved in attentional or emotional tinnitus modulation and provides deeper mechanistic insights into how and through which channels phantom sound perception might be modulated on a neuronal level.

EEG alpha power during creative ideation of graphic symbols

Graphic symbolic creation-transforming abstract concepts into visual forms-is a cognitively complex and uniquely human skill. Neurophysiological evidence suggests that oscillatory alpha activity is correlated with visual-figurative creative thinking. However, whether alpha oscillations play a functional role in generating graphic symbols remains unclear. To address this issue, we compared the EEG alpha power of 40 healthy adults while ideating creative and conventional graphic symbols representing an abstract concept's meaning (e.g., the word 'peace'). Our results revealed that the ideation of graphic symbols elicited alpha synchronization, with higher levels in the conventional compared to the creative condition, mainly over frontal-central, frontal-temporal, parietal-occipital, and occipital regions. Furthermore, we observed greater alpha synchronization in the right hemisphere than in the left across both conditions, particularly between temporal, central-parietal, and parietal electrodes. This asymmetry extended to central electrodes in the creative condition, while in the conventional condition, it was more pronounced over parietal-occipital regions. Finally, we also found that frontal and occipital alpha synchronization during the creative ideation phase predicted the subsequent originality scores of the graphic symbols produced. Together, these findings enhance our understanding of the dynamics of oscillatory alpha activity during graphic symbol creation, shedding light on how the interaction between inhibitory top-down control mechanisms and cognitive flexibility processes facilitates the transformation of abstract concepts into visual forms. These findings provide new insights into the neural processes underlying this uniquely human ability.

The consequences of color chromaticity on electrophysiological measures of attentional deployment in visual search

We investigated to what extent color vividness of visual items influences how humans prioritize information in a search task. For this, color chromaticity was manipulated over two search experiments. While recording the electroencephalogram, participants searched for a shape of certain color among three other shapes, when it emerged from a stream of flickering gray placeholders. Each location was tagged with a specific frequency evoking the steady-state-visual-evoked potential (SSVEP) allowing to track attentional deployment on multiple items. Color vividness boosted SSVEP amplitudes independent of item type, i.e., targets or distractors, while leaving other measures of attentional deployment-event-related potentials and alpha-band amplitudes-mostly unaffected. Interestingly, relative modulation of target and distractor SSVEP amplitudes was comparable between experiments suggesting similar attentional deployment. The results highlight that attentional deployment to search items depends on low-level stimulus features that need to be controlled to allow for inferences about capture or suppression of individual items.

Dissociating external and internal attentional selection

Just as attention can shift externally toward relevant objects in the visual environment, it can shift internally toward relevant items within Visual Working Memory (VWM). Recent work has shown that spatial attention is automatically directed toward the previous location of an attended memory item, as it is to locations of perceived stimuli. When attending memory items, however, there is no sensory information to be processed at the previous location. Thus, we asked whether internal attention-akin to external attention-modulates sensory processing. In two EEG experiments, we compared location-specific sensory enhancements during attentional selection of external (perceived) versus internal (memorized) stimuli. Alpha-power and gaze-position biases confirmed an inherent spatial organization within VWM. However, Rapid Invisible Frequency Tagging (RIFT) revealed sensory modulation only during external attentional selection. Thus, VWM is not blindly recruiting existing mechanisms of external attention, but instead uses space as an organizational principle to store and select memories.

Traveling waves in the human visual cortex: An MEG-EEG model-based approach

Brain oscillations might be traveling waves propagating in cortex. Studying their propagation within single cortical areas has mostly been restricted to invasive measurements. Their investigation in healthy humans, however, requires non-invasive recordings, such as MEG or EEG. Identifying traveling waves with these techniques is challenging because source summation, volume conduction, and low signal-to-noise ratios make it difficult to localize cortical activity from sensor responses. The difficulty is compounded by the lack of a known ground truth in traveling wave experiments. Rather than source-localizing cortical responses from sensor activity, we developed a two-part model-based neuroimaging approach: (1) The putative neural sources of a propagating oscillation were modeled within primary visual cortex (V1) via retinotopic mapping from functional MRI recordings (encoding model); and (2) the modeled sources were projected onto MEG and EEG sensors to predict the resulting signal using a biophysical head model. We tested our model by comparing its predictions against the MEG-EEG signal obtained when participants viewed visual stimuli designed to elicit either fovea-to-periphery or periphery-to-fovea traveling waves or standing waves in V1, in which ground truth cortical waves could be reasonably assumed. Correlations on within-sensor phase and amplitude relations between predicted and measured data revealed good model performance. Crucially, the model predicted sensor data more accurately when the input to the model was a traveling wave going in the stimulus direction compared to when the input was a standing wave, or a traveling wave in a different direction. Furthermore, model accuracy peaked at the spatial and temporal frequency parameters of the visual stimulation. Together, our model successfully recovers traveling wave properties in cortex when they are induced by traveling waves in stimuli. This provides a sound basis for using MEG-EEG to study endogenous traveling waves in cortex and test hypotheses related with their role in cognition.

Standardized low-resolution brain electromagnetic tomography does not improve EEG Alzheimer's disease assessment

Quantitative EEG has been shown to reflect neurodegenerative processes in Alzheimer's disease (AD) and may provide non-invasive and widely available biomarkers to enhance the objectivization of disease assessment. To address EEG's major drawback - its low spatial resolution - many studies have employed 3D source localization. However, none have investigated whether this complex mapping into 3D space actually adds value over standard surface derivation. In fact, we found no prior study - in any disease - that quantitatively compared the results of a 3D source localization method with those achieved by surface derivation. We analyzed data from one of the largest prospective AD EEG studies ever conducted (four study centers, 188 patients, 100 female). Thousands of distinct quantitative EEG markers of slowing, complexity, and functional connectivity were computed and regressed against disease severity, with rigorous control for multiple testing. We found highly significant associations between quantitative EEG markers and disease severity. However, standardized low-resolution electromagnetic tomography (sLORETA), a widely used 3D source localization method, did not improve results. Furthermore, a surface derivation marker (auto-mutual information of the left hemisphere during the eyes-closed condition) was the best performing marker across our entire sample. While our findings strongly support that quantitative EEG markers reflect neurodegenerative processes in AD, they do not demonstrate additional benefit from sLORETA. Importantly, our results are specific to AD and sLORETA. Therefore, they should not be generalized to other neurological or psychiatric disorders or to other 3D source localization methods without further validation. Finally, these findings do not diminish the value of 3D source localization for visual EEG inspection.

A comprehensive investigation of intracortical and corticothalamic models of the alpha rhythm

The electroencephalographic alpha rhythm is one of the most robustly observed and widely studied empirical phenomena in all of neuroscience. However, despite its extensive implication in a wide range of cognitive processes and clinical pathologies, the mechanisms underlying alpha generation in neural circuits remain poorly understood. In this paper we offer a renewed foundation for research on this question, by undertaking a systematic comparison and synthesis of the most prominent theoretical models of alpha rhythmogenesis in the published literature. We focus on four models, each studied intensively by multiple authors over the past three decades: (i) Jansen-Rit, (ii) Moran-David-Friston, (iii) Robinson-Rennie-Wright, and (iv) Liley-Wright. Several common elements are identified, such as the use of second-order differential equations and sigmoidal potential-to-rate operators to represent population-level neural activity. Major differences are seen in other features such as wiring topologies and conduction delays. Through a series of mathematical analyses and numerical simulations, we nevertheless demonstrate that the selected models can be meaningfully compared, by associating parameters and circuit motifs of analogous biological significance. With this established, we conduct explorations of rate constant and synaptic connectivity parameter spaces, with the aim of identifying common patterns in key behaviours, such as the role of excitatory-inhibitory interactions in the generation of oscillations. Finally, using linear stability analysis we identify two qualitatively different alpha-generating dynamical regimes across the models: (i) noise-driven fluctuations and (ii) self-sustained limit-cycle oscillations, emerging due to an Andronov-Hopf bifurcation. The comprehensive survey and synthesis developed here can, we suggest, be used to help guide future theoretical and experimental work aimed at disambiguating these and other candidate theories of alpha rhythmogenesis.

Test-retest reliability of pre-cue and anticipatory alpha activity in visual spatial attention

Alpha-band activity over the parietal-occipital cortex is a canonical neural marker of visual spatial attention. However, the ongoing debate surrounds whether this activity represents as an active mechanism in gating visual information processing or if it merely reflects an epiphenomenal consequence of anticipatory attentional shifts. Despite this debate, the temporal stability of alpha activity in visual spatial attention, an essential aspect for this discussion, remains ambiguous. Notably, our recent findings highlighted the significant impact of pre-cue alpha power on anticipatory alpha activity in spatial attention tasks, yet the reliability of these pre-cue alpha effects remained unexplored. Here we evaluated the short-term test-retest reliability of both pre-cue and anticipatory alpha activity in healthy young adults who engaged in the same spatial cueing paradigm over two consecutive days. Reliability was gauged using the intraclass coefficient (ICC). Our results demonstrated excellent reliability of pre-cue alpha power, alpha event-related desynchronization (ERD) and individual alpha frequency (IAF), and moderate reliability of alpha lateralization index (LI). Additionally, by categorizing participants into higher and lower pre-cue alpha power sub-groups based on median-splitting, we observed no significant differences in ICCs between the two sub-groups for anticipatory alpha ERD, LI and IAF, except for a significantly higher ICC of pre-cue alpha power in the higher sub-group than the lower sub-group. Taken together, by examining the short-term reliability of alpha-band activity in visual spatial attention for the first time, our study lays a foundational step for the ongoing discourse regarding its functional implications in visual spatial attention.

Top-down and bottom-up interactions rely on nested brain oscillations to shape rhythmic visual attention sampling

Adaptive visual processing is enabled through the dynamic interplay between top-down and bottom-up (feedback/feedforward) information exchange, presumably propagated through brain oscillations. Here, we causally tested for the oscillatory mechanisms governing this interaction in the human visual system. Using concurrent transcranial magnetic stimulation-electroencephalography (TMS-EEG), we emulated top-down signals by a single TMS pulse over the frontal eye field (right FEF), while manipulating the strength of sensory input through the presentation of moving concentric gratings (compared to a control-TMS site). FEF-TMS without sensory input led to a top-down modulated occipital phase realignment, alongside higher fronto-occipital phase connectivity, in the alpha/beta band. Sensory input in the absence of FEF-TMS increased occipital gamma activity. Crucially, testing the interaction between top-down and bottom-up processes (FEF-TMS during sensory input) revealed an increased nesting of the bottom-up gamma activity in the alpha/beta-band cycles. This establishes a causal link between phase-to-power coupling and top-down modulation of feedforward signals, providing novel mechanistic insights into how attention interacts with sensory input at the neural level, shaping rhythmic sampling.

Hemisphere- and condition-specific alpha oscillations support semantic and spatial cognition in aging

Neuroimaging studies have shown age-related alterations in brain structure and function supporting semantic knowledge, although the significance of these is not fully understood. Herein, we report novel temporal, spectral, and spatial information on age-related changes from the largest dynamic functional mapping study of semantic processing. Participants (N = 130, age range 21-87 years, Mage = 51.05, SD = 14.73, 68 females) performed a semantic judgement task during magnetoencephalography (MEG), and significant task-related oscillatory responses were projected into anatomical space using a beamformer. Voxel-wise linear mixed-effects models were performed to assess semantic-related neural oscillations, irrespective of and influenced by age. Mediation analyses were performed to assess if local oscillations mediated the relationship between age and reaction time. Whole-brain analyses revealed stronger left-lateralized alpha/beta oscillations in frontotemporal cortices during semantic trials and stronger right-lateralized alpha/beta responses in temporoparietal regions during length trials (all ps <.001). Older adults showed stronger left temporoparietal alpha and left frontal beta during semantic processing and stronger alpha in the right temporal cortex during the length condition (all ps <.001). Alpha oscillations further mediated the relationship between age and reaction time in a hemisphere- and condition-specific manner, whereby right temporal activity mediated the age-behavior relationship in the length but not semantic condition (Z = 2.01, p =.022), while left temporoparietal activity significantly mediated this relationship in the semantic but not length condition (Z =  - 2.41, p =.008). Altogether, our findings demonstrate accentuated oscillations in aging which are hemisphere- and condition-specific and support compensatory processing to aid in maintaining adequate behavioral performance, lending clear support to leading neuroscientific models of aging.

The impact of hyperventilation on brain alpha activity: An EEG study

Hyperventilation (HV) is a major physiological risk factor in environments like high altitudes or hypoxic conditions, causing a range of physiological changes that can potentially impair cognitive functions. As an important bridge connecting brain physiological states and cognitive functions, the variation of alpha activity under the effect of HV has not been fully explored. To this end, this work aims to reveal the changes in EEG alpha activity induced by HV in terms of power spectrum and functional connectivity (FC). EEG data were recorded from 305 healthy young male subjects when they were under three stages: Pre-HV, HV, and Post-HV. Then, EEG power spectrum was estimated and adjusted by removing the aperiodic components. The alpha peak frequency (APF) and adjusted alpha peak frequency (aAPF) were both slowed from Pre-HV to HV and recovered in Post-HV, which revealed a U-shaped trend. Both the alpha peak power (AP) and adjusted alpha peak power (aAP) decreased during HV. FC was assessed via the weighted Phase Lag Index (wPLI), which exhibited a HV-related decrease followed by an increase in Post-HV, with a rightward lateralization shift. In summary, both the power spectrum and FC metrics showed a U-shaped tendency, suggesting a negative impact of HV on alpha activity. Our findings provide some of the first quantitative insights into the effects of HV on alpha activity, further confirming the regulatory patterns of HV on neural activity.

Neural activity is modulated by spontaneous and volitionally controlled breathing

Recent studies have provided evidence regarding respiration-brain coupling, but our understanding of how continuously varying dynamics of breathing modulate neural activity remains incomplete. We examined whether the neural state differs between spontaneous and volitionally controlled breathing and across the phases of breathing, inspiration and expiration. Magnetoencephalography (MEG) with a respiratory belt was used to record cortical oscillatory activity during spontaneous, deep, and square breathing (n = 33). Additionally, self-report measures of mood and arousal were applied to assess changes in the psychological state during the breathing techniques. Alpha power was suppressed during inspiration and increased during expiration (p < .01) indicating dynamically fluctuating neural states across the respiratory cycle. This effect was observed in the sensorimotor areas during both spontaneous and volitionally controlled deep breathing. Compared to spontaneous and volitionally controlled square breathing, alpha power increased during deep breathing (p < .01) within a cortical network extending to frontal and temporal areas. We also observed a steeper aperiodic slope and a broadband shift in the power spectrum in the left superior frontal gyrus during square breathing in comparison with spontaneous breathing suggesting that not only oscillatory activity but also the more general spectral characteristics of ongoing neural activity are modulated by the rate, depth, and pattern of breathing. Self-reported mood and arousal did not differ across the breathing techniques. Altogether, we demonstrate that neural activity is modulated by the phases of breathing and can also be volitionally influenced by varying the rate, depth, and pattern of breathing.

Investigating the Human Brain's Integration of Internal and External Reference Frames: The Role of the Alpha and Beta Bands in a Modified Temporal Order Judgment Task

The integration of the internal and external reference frames of the human brain is crucial for achieving accurate tactile spatial localization. However, the mechanisms underlying this integration have yet to be fully elucidated. This study adopted a modified temporal order judgment paradigm with an advanced weighted phase lag index method to investigate brain network interactions when the internal and external reference frames were integrated. We found that when the brain integrated internal and external reference frames, alpha oscillations decreased, beta oscillations increased, and inter-hemispheric connectivity increased. Specifically, compared with the match condition: first, the alpha band oscillation predominantly contributed to processing the internal reference frame mismatch; second, the alpha and late beta band oscillation predominantly contributed to processing the external reference frame mismatch; third, the early alpha and late beta band oscillation predominantly contributed to processing the internal and external reference frame mismatch. These findings suggest that the neural oscillation of the alpha and beta bands plays an essential role in tactile spatial localization.

The Interoceptive Brain: Confidence Ratings and Accuracy Scores are Independently and Differently Associated With Task-Related Alpha Power During the Heartbeat Tracking Task

Cardiac interoception is important for health and can be assessed in terms of accuracy (IAcc) and sensibility (IS), at least. While IAcc measures the correspondence between recorded and perceived heartbeats, IS means the confidence in interoceptive perceptions during the task. The present study investigated if brain activity during the heartbeat tracking task is associated with IAcc as well as IS. Specifically, we were interested if task-related power (TRP) in the alpha band (8-12 Hz), known to indicate task-specific cognitive functions such as semantic, attentional, and sensory processes, is associated with IAcc and IS, respectively. In a sample of 30 participants, we found relatively higher TRP in the alpha band over left temporal and parietal areas (vs. right) during the interoception task. Furthermore, we observed a negative association between TRP in the alpha band and IS. Lower TRP in the alpha band might indicate that more pronounced cognitive and sensory processes are linked to higher IS. Furthermore, we found a positive effect for IAcc (independent from IS), which might indicate that more internal attention during the interoception task is beneficial for IAcc. We further discuss the findings in the context of methodological issues of the heartbeat tracking task. Taken together, the pattern of findings favors the investigation of task-related IS (i.e., confidence ratings) in combination with IAcc to gain a better access to interoceptive processes and to improve our understanding of the neural underpinnings of (cardiac) interoception.

Distinct age-related alterations in alpha-beta neural oscillatory activity during verbal working memory encoding in children and adolescents

Emerging imaging studies of working memory (WM) have identified significant WM-related oscillatory events that are unique to each phase of working memory (e.g. encoding, maintenance). Although many previous imaging studies have shown age-related changes within the frontoparietal network when performing a WM task, understanding of the age-related changes in the oscillatory dynamics underlying each phase of WM during development and their relationships to other cognitive function is still in its infancy. To this end, we enrolled a group of 74 typically-developing youths aged 7-15 years to perform a letter-based Sternberg WM task during magnetoencephalography. Trial-wise data were transformed into the time-frequency domain, and significant oscillatory responses during the encoding and maintenance phases of the task were independently imaged using beamforming. Our results revealed widespread age-related power differences in alpha-beta oscillatory activity during encoding throughout left frontal, parietal, temporal, occipital and cerebellar regions. By contrast, age-related differences in maintenance-related activity were limited to a small area in the superior temporal gyrus and parieto-occipital regions. Follow-up exploratory factor analysis of age-related encoding alpha-beta activity revealed two distinct factors, and these factors were each found to significantly mediate age-related improvements in both verbal and non-verbal cognitive ability. Additionally, late maintenance alpha activity was related to reaction time on the task. Taken together, our results indicate that the neural dynamics in the alpha and beta bands are uniquely sensitive to age-related changes throughout this developmental period and are related to both task performance and other aspects of cognitive development. KEY POINTS: Understanding of the age-related changes in neural oscillatory dynamics serving verbal working memory function is in its infancy. This study identified the age-related neural alterations during each phase of working memory processing in youths. Developmental differences during working memory processing were primarily isolated to alpha-beta activity during the encoding phase. Alpha-beta activity during encoding significantly mediated age-related improvements in both verbal and non-verbal ability. This study establishes new brain-behaviour relationships linking working memory function to other aspects of cognitive development.

Neurophysiological Responses to Vicarious Affective Touch: An Electroencephalography (EEG) Study

Affective touch is a somatosensory modality involved in forming and consolidating rewarding social interactions and is hypothesised to be encoded by a population of cutaneous unmyelinated low threshold mechanosensory C-tactile afferents (CT). CTs are preferentially activated by a caressing type of touch delivered at speeds around 3 cm/s (CT-optimal speed) and at skin temperature. Given its social relevance, the vicarious observation of affective touch can cause high empathic resonance in the observer. However, little is known whether the observation of CT-optimal touch is processed differently in the observer's brain than at other CT-suboptimal speeds. In our study, we evaluated subjective reports of the pleasantness/willingness of observers to receive such touch while recording the electroencephalogram (EEG) as they watched touch videos at three different speeds: static, slow (CT-optimal), and fast touch. We found that CT-optimal touch was rated as more pleasant and elicited greater willingness to engage, compared to static or fast touch. CT-optimal touch also led to significantly lower beta power, reflecting greater EEG desynchronisation, compared to the other conditions. Other frequency bands, such as theta and alpha, showed increased modulation to slow and fast touch compared to static touch. However, no differences were found between slow and fast conditions in the alpha and theta bands. Our results suggest that vicarious processing of affective touch at the optimal speed for CT receptors involves broader neural resources and higher activation of somatosensory areas, highlighting the significance of this touch modality in sensory processing.

The Neural Oscillatory Basis of Perspective-Taking in Autistic and Non-Autistic Adolescents Using Magnetoencephalography

Taking another's perspective is a high-level mental skill underlying many aspects of social cognition. Perspective-taking is usually an embodied egocentric process whereby people mentally rotate themselves away from their physical location into the other's orientation. This is accompanied by increased theta-band (3-7 Hz) brain oscillations within a widespread fronto-parietal cortical network including the temporoparietal junction. Individuals with autism spectrum conditions (ASC) have been reported to experience challenges with high-level perspective-taking, particularly when adopting embodied strategies. To investigate the potential neurophysiological basis of these autism-related individual differences, we used magnetoencephalography in combination with a well-replicated perspective-taking paradigm in a group of 18 autistic and 17 age-matched non-autistic adolescents. Findings revealed that increasing the angle between self and other perspective resulted in prolonged reaction times for the autistic group during perspective-taking. This was accompanied by reduced theta power across a wide network of regions typically active during social cognitive tasks. On the other hand, the autistic group showed greater alpha power decreases in visual cortex compared with the non-autistic group across all perspective-taking conditions. These divergent theta and alpha power effects, coupled with steeper response time slopes, suggest that autistic individuals may rely more on alternative cognitive strategies, such as mental object rotation, rather than an egocentric embodied approach. Finally, no group differences were found when participants were asked to track, rather than take, another's viewpoint, suggesting that autism-related individual differences are specific to high-level perspective-taking.

The Role of Fronto-Central Theta Oscillations in Inter-Sensory Selective Attention

Selective attention supports top-down control by biasing information processing toward stimuli that are potentially relevant to the immediate goal. It has been recently proposed that theta band oscillations (~4-8 Hz) in the frontal midline regions are a key mechanism of endogenous selective attention. The current electroencephalography study investigated theta oscillatory dynamics using an inter-sensory cueing paradigm in which a symbolic cue indicated, on a trial-by-trial basis, the modality (visual or auditory) of the upcoming discrimination task. Time-frequency analyses were used to quantify phase- (evoked) and non-phase-locked (induced) fronto-central theta activity during preparatory attentional states. In a sample of 20 young adult participants, we found that those who relied on the cues to selectively attend to the sensory modality of the discrimination task performed more efficiently (i.e., faster and with greater accuracy) and presented greater non-phase-locked fronto-central theta power 200-400 ms post-cue onset. Moreover, greater non-phase-locked theta oscillations were associated with better behavioral performance. Secondary analyses on alpha oscillations revealed concomitant brain activity to theta with a pronounced decrease in alpha power in fronto-central regions, without significant effect on task performance. These findings suggest that increased non-phase-locked fronto-central theta oscillations are a neuronal correlate of preparatory attentional control and that the interplay of theta-alpha rhythms differentially contributes to attentional and perceptual aspects.

The role of alpha oscillations in resisting distraction

The role of alpha oscillations (8-13 Hz) in suppressing distractors is extensively debated. One debate concerns whether alpha oscillations suppress anticipated visual distractors through increased power. Whereas some studies suggest that alpha oscillations support distractor suppression, others do not. We identify methodological differences that may explain these discrepancies. A second debate concerns the mechanistic role of alpha oscillations. We and others previously proposed that alpha oscillations implement gain reduction in early visual regions when target load or distractor interference is high. Here, we suggest that parietal alpha oscillations support gating or stabilization of attentional focus and that alpha oscillations in ventral attention network (VAN) support resistance to attention capture. We outline future studies needed to uncover the precise mechanistic role of alpha oscillations.

Prediction of acoustic tinnitus suppression using resting-state EEG via explainable AI approach

Tinnitus is defined as the perception of sound without an external source. Its perceptual suppression or on/off states remain poorly understood. This study investigates neural traits linked to brief acoustic tinnitus suppression (BATS) using naive resting-state EEG (closed eyes) from 102 individuals. A set of EEG features (band power, entropy, aperiodic slope and offset of the EEG spectrum, and connectivity) and standard classifiers were applied achieving consistent high accuracy across data splits: 98% for sensor and 86% for source models. The Random Forest model outperformed other classifiers by excelling in robustness and reduction of overfitting. It identified several key EEG features, most prominently alpha and gamma frequency band power. Gamma power was stronger in the left auditory network, while alpha power dominated the right hemisphere. Aperiodic features were normalized in individuals with BATS. Additionally, hyperconnected auditory-limbic networks in BATS suggest sensory gating may aid suppression. These findings demonstrate robust classification of BATS status, revealing distinct neural traits between tinnitus subpopulations. Our work emphasizes the role of neural mechanisms in predicting and managing tinnitus suppression. Moreover, it advances the understanding of effective feature selection, model choice, and validation strategies for analyzing clinical neurophysiological data in general.

EEG oscillations reveal neuroplastic changes in pain processing associated with long-term meditation

The experience of pain is a combined product of bottom-up and top-down influences mediated by attentional and emotional factors. Meditation states and traits are characterized by enhanced attention/emotion regulation and expanded self-awareness that can be expected to modify pain processing. The main objective of the present study was to explore the effects of long-term meditation on neural mechanisms of pain processing. EEG pain-related oscillations (PROs) were analysed in highly experienced practitioners and novices during a non-meditative resting state with respect to (a) local frequency-specific and temporal synchronizing characteristics to reflect mainly bottom-up mechanisms, (b) spatial synchronizing patterns to reflect the neural communication of noxious information, (c) pre-stimulus oscillations to reflect top-down mechanisms during pain expectancy, and (d) the P3b component of the pain-related potential to compare the emotional/cognitive reappraisal of pain events by expert and novice meditators. Main results demonstrated that in experienced (long-term) meditators as compared to non-experienced (short-term) meditators (1) the temporal and spatial synchronizations of multispectral (from theta-alpha to gamma) PROs were substantially suppressed at primary and secondary somatosensory regions contra-lateral to pain stimulation within 200 ms after noxious stimulus; (2) pre-stimulus alpha activity was significantly increased at the same regions, which predicted the suppressed synchronization of PROs in long-term meditators; (3) the decrease of the P3b component was non-significant. These novel observations provide evidence that even when subjected to pain outside of meditation, experienced meditators exhibit a pro-active top-down inhibition of somatosensory areas resulting in suppressed processing and communication of sensory information at early stages of painful input. The emotional/cognitive appraisal of pain is reduced but remains preserved revealing a capacity of experienced meditators to dissociate pro-active and reactive top-down processes during pain control.

Motor imagery EEG microstates are influenced by alpha power

Electroencephalogram (EEG) microstates are pivotal in understanding brain dynamics, reflecting transitions between global states. These parameters undergo selective inhibition within cortical areas, modulated by alpha oscillations. This study investigates how alpha band power influences microstate parameters across various task conditions, including resting state, actual motor execution, and imagined motor tasks. By comparing these three conditions, we aim to elucidate the distinct effects of alpha power on microstate dynamics, as each condition represents a unique pattern of brain activity. Motor imagery (MI) induces event-related desynchronization/synchronization, modulating Mu (alpha) and Beta rhythms in sensorimotor areas. However, the relationship between MI-EEG microstates and alpha power remains unclear. Our results show that alpha power was highest in resting state, followed by imagined motion, and lowest during actual motion. As alpha power increased, microstate A parameters in resting state (occurrence, coverage) decreased, while those in actual motion increased. Additionally, microstate B parameters rose with alpha power in resting state but decreased during imagined motion. Notably, alpha power correlated more strongly with microstate parameters in task states than in resting state. In addition, alpha, theta, and beta powers during task performance were negatively correlated with the duration of microstates A, B, and C, while being positively correlated with the occurrence of microstates A, B, C, and D. These findings suggest that alpha power influences microstate parameters differently depending on the brain, underscoring the significance of inter-band interactions in shaping microstate dynamics.

Frontal gamma-alpha ratio reveals neural oscillatory mechanism of attention shifting in tinnitus

In clinical practice, the symptoms of tinnitus patients can be temporarily alleviated by diverting their attention away from disturbing sounds. However, the precise mechanisms through which this alleviation occurs are still not well understood. Here, we aimed to directly evaluate the role of attention in tinnitus alleviation by conducting distraction tasks with multilevel loads and resting-state tests among 52 adults with tinnitus and 52 healthy controls. We demonstrated that the abnormal neural oscillations in tinnitus subjects, reflected in an altered gamma/alpha ratio index in the frontal lobe, could be regulated by attention shifting in a linear manner for which the regulatory effect increased with the load of distraction. Quantitative measures of the regulation significantly correlated with symptom severity. Altogether, our work provides proof-of-concept for the role of attention in tinnitus perception and lays a solid foundation to support evidence-based applications of attention shifting in clinical interventions for tinnitus.

Targeting Neural Oscillations for Cognitive Enhancement in Alzheimer's Disease

Alzheimer's disease (AD), the most prevalent form of dementia, is marked by progressive cognitive decline, affecting memory, language, orientation, and behavior. Pathological hallmarks include extracellular amyloid plaques and intracellular tau tangles, which disrupt synaptic function and connectivity. Neural oscillations, the rhythmic synchronization of neuronal activity across frequency bands, are integral to cognitive processes but become dysregulated in AD, contributing to network dysfunction and memory impairments. Targeting these oscillations has emerged as a promising therapeutic strategy. Preclinical studies have demonstrated that specific frequency modulations can restore oscillatory balance, improve synaptic plasticity, and reduce amyloid and tau pathology. In animal models, interventions, such as gamma entrainment using sensory stimulation and transcranial alternating current stimulation (tACS), have shown efficacy in enhancing memory function and modulating neuroinflammatory responses. Clinical trials have reported promising cognitive improvements with repetitive transcranial magnetic stimulation (rTMS) and deep brain stimulation (DBS), particularly when targeting key hubs in memory-related networks, such as the default mode network (DMN) and frontal-parietal network. Moreover, gamma-tACS has been linked to increased cholinergic activity and enhanced network connectivity, which are correlated with improved cognitive outcomes in AD patients. Despite these advancements, challenges remain in optimizing stimulation parameters, individualizing treatment protocols, and understanding long-term effects. Emerging approaches, including transcranial pulse stimulation (TPS) and closed-loop adaptive neuromodulation, hold promise for refining therapeutic strategies. Integrating neuromodulation with pharmacological and lifestyle interventions may maximize cognitive benefits. Continued interdisciplinary efforts are essential to refine these approaches and translate them into clinical practice, advancing the potential for neural oscillation-based therapies in AD.

A human electrophysiological biomarker of Fragile X Syndrome is shared in V1 of Fmr1 KO mice and caused by loss of FMRP in cortical excitatory neurons

Predicting clinical therapeutic outcomes from preclinical animal studies remains an obstacle to developing treatments for neuropsychiatric disorders. Electrophysiological biomarkers analyzed consistently across species could bridge this divide. In humans, alpha oscillations in the resting state electroencephalogram (rsEEG) are altered in many disorders, but these disruptions have not yet been characterized in animal models. Here, we employ a uniform analytical method to show in males with fragile X syndrome (FXS) that the slowed alpha oscillations observed in adults are also present in children and in visual cortex of adult and juvenile Fmr1 -/y mice. We find that alpha-like oscillations in mice reflect the differential activity of two classes of inhibitory interneurons, but the phenotype is caused by deletion of Fmr1 specifically in cortical excitatory neurons. These results provide a framework for studying alpha oscillation disruptions across species, advance understanding of a critical rsEEG signature in the human brain and inform the cellular basis for a putative biomarker of FXS.

Distinct Alpha Networks Modulate Different Aspects of Perceptual Decision-Making

Why do we sometimes perceive a faint stimulus but miss it at other times? One explanation is that conscious perception fluctuates with the brain's internal state, influencing how external stimuli are processed. Ongoing brain oscillations in the alpha band (8-13 Hz), thought to reflect neuronal excitability levels1-5 and play a role in functional inhibition6,7, have been shown as a key contributor to such perceptual variability8,9. Under high alpha conditions, faint stimuli are more likely to be missed8. Some studies suggested alpha oscillations modulate perceptual criterion ( c ) 10-14, shifting the threshold for interpreting sensory information; while others (including our prior work15) suggested alpha modulates sensitivityd ' 15-19, changing the precision of sensory encoding. Few studies observed modulations in both metrics, making these results appear mutually exclusive. Most studies have focused solely on overall alpha activity-whether within a region of interest or across the whole brain-and overlooked the coexistence of multiple distinct alpha networks20-26, which fluctuate in terms of predominance20,27,28 and adapt to behavioural demands29,30. Hence, it remained unclear whether different networks' contributions to perception vary with their momentary state. Here, aiming to characterize how different alpha networks influence perceptual decision-making, we analyzed magnetoencephalography (MEG) data recorded while participants performed a visual detection task with threshold-level stimuli. We found that while the visual alpha network modulates perceptual sensitivity, the sensorimotor alpha network modulates criterion in perceptual decision-making. These findings reconcile previous conflicting results and highlight the functional diversity of alpha networks in shaping perception.

Entrainment by transcranial alternating current stimulation: Insights from models of cortical oscillations and dynamical systems theory

Signature of neuronal oscillations can be found in nearly every brain function. However, abnormal oscillatory activity is linked with several brain disorders. Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that can potentially modulate neuronal oscillations and influence behavior both in health and disease. Yet, a complete understanding of how interacting networks of neurons are affected by tACS remains elusive. Entrainment effects by which tACS synchronizes neuronal oscillations is one of the main hypothesized mechanisms, as evidenced in animals and humans. Computational models of cortical oscillations may shed light on the entrainment effects of tACS, but current modeling studies lack specific guidelines to inform experimental investigations. This study addresses the existing gap in understanding the mechanisms of tACS effects on rhythmogenesis within the brain by providing a comprehensive overview of both theoretical and experimental perspectives. We explore the intricate interactions between oscillators and periodic stimulation through the lens of dynamical systems theory. Subsequently, we present a synthesis of experimental findings that demonstrate the effects of tACS on both individual neurons and collective oscillatory patterns in animal models and humans. Our review extends to computational investigations that elucidate the interplay between tACS and neuronal dynamics across diverse cortical network models. To illustrate these concepts, we conclude with a simple oscillatory neuron model, showcasing how fundamental theories of oscillatory behavior derived from dynamical systems, such as phase response of neurons to external perturbation, can account for the entrainment effects observed with tACS. Studies reviewed here render the necessity of integrated experimental and computational approaches for effective neuromodulation by tACS in health and disease.

Assessing Trial-by-Trial Electrophysiological and Behavioral Markers of Attentional Control and Sensory Precision in Psychotic and Mood Disorders

BACKGROUND AND HYPOTHESIS

The current study investigated the extent to which changes in attentional control contribute to performance on a visual perceptual discrimination task, on a trial-by-trial basis in a transdiagnostic clinical sample.

STUDY DESIGN

Participants with schizophrenia (SZ; N = 58), bipolar disorder (N = 42), major depression disorder (N = 51), and psychiatrically healthy controls (N = 92) completed a visual perception task in which stimuli appeared briefly. The design allowed us to estimate the lapse rate and the precision of perceptual representations of the stimuli. Electroencephalograms (EEG) were recorded to examine pre-stimulus activity in the alpha band (8-13 Hz), overall and in relation to behavior performance on the task.

STUDY RESULTS

We found that the attention lapse rate was elevated in the SZ group compared with all other groups. We also observed group differences in pre-stimulus alpha activity, with control participants showing the highest levels of pre-stimulus alpha when averaging across trials. However, trial-by-trial analyses showed within-participant fluctuations in pre-stimulus alpha activity significantly predicted the likelihood of making an error, in all groups. Interestingly, our analysis demonstrated that aperiodic contributions to the EEG signal (which affect power estimates across frequency bands) serve as a significant predictor of behavior as well.

CONCLUSIONS

These results confirm the elevated attention lapse rate that has been observed in SZ, validate pre-stimulus EEG markers of attentional control and their use as a predictor of behavior on a trial-by-trial basis, and suggest that aperiodic contributions to the EEG signal are an important target for further research in this area, in addition to alpha-band activity.

White matter microstructure as a potential contributor to differences in resting state alpha activity between neurotypical and autistic children: a longitudinal multimodal imaging study

We and others have demonstrated the resting-state (RS) peak alpha frequency (PAF) as a potential clinical marker for young children with autism spectrum disorder (ASD), with previous studies observing a higher PAF in school-age children with ASD versus typically developing (TD) children, as well as an association between the RS PAF and measures of processing speed in TD but not ASD. The brain mechanisms associated with these findings are unknown. A few studies have found that in children more mature optic radiation white matter is associated with a higher PAF. Other studies have reported white matter and neural activity associations in TD but not ASD. The present study hypothesized that group differences in the RS PAF are due, in part, to group differences in optic radiation white matter and PAF associations. The maturation of the RS PAF (measured using magnetoencephalography(MEG)), optic radiation white matter (measured using diffusion tensor imaging(DTI)), and associations with processing speed were assessed in a longitudinal cohort of TD and ASD children. Time 1 MEG and DTI measures were obtained at 6-8 years old (59TD and 56ASD) with follow-up brain measures collected ~ 1.5 and ~ 3 years later. The parietal-occipital PAF increased with age in both groups by 0.13 Hz/year, with a main effect of group showing the expected higher PAF in ASD than TD (an average of 0.26 Hz across the 3 time points). Across age, the RS PAF predicted processing speed in TD but not ASD. Finally, more mature optic radiation white matter measures (FA, RD, MD, AD) were associated with a higher PAF in both groups. Present findings provide additional evidence supporting the use of the RS PAF as a brain marker in children with ASD 6-10 years old, and replicate findings of an association between the RS PAF and processing speed in TD but not ASD. The hypothesis that the RS PAF group differences (with ASD leading TD by about 2 years) would be explained by group differences in optic radiation white matter was not supported, with brain structure-function associations indicating that more mature optic radiation white matter is associated with a higher RS PAF in both groups.

Neurophysiological insights into catecholamine-dependent tDCS modulation of cognitive control

Goal-directed behavior requires resolving both consciously and subconsciously induced response conflicts. Neuronal gain control, which enhances processing efficacy, is crucial for conflict resolution and can be increased through pharmacological or brain stimulation interventions, though it faces inherent physical limits. This study examined the effects of anodal transcranial direct current stimulation (atDCS) and methylphenidate (MPH) on conflict processing. Healthy adults (n = 105) performed a flanker task, with electroencephalography (EEG) used to assess alpha and theta band activity (ABA, TBA). Results showed that combining atDCS with MPH enhanced cognitive control and reduced response conflicts more effectively than atDCS alone, particularly when both conflict types co-occurred. Both atDCS and atDCS + MPH exhibited similar task-induced ABA and TBA modulations in the (pre)supplementary motor area, indicating heightened gain control. Overlapping neuroanatomical effects in mid-superior frontal areas suggest that atDCS and MPH share a common neuronal mechanism of gain control, especially in high-conflict/-demand situations.

Investigating the Consistency of Negative BOLD Responses to Combinations of Visual, Auditory, and Somatosensory Stimuli and Their Modulation by the Level of Task Demand

Negative BOLD fMRI responses (NBR) occur commonly in sensory cortex and default mode network regions but remain poorly utilized as a marker of brain function due to an incomplete understanding. To better understand how NBR manifest across the brain, compare between different sensory stimuli and how they are modulated by changes in task demand, we recorded fMRI during trials of visual, auditory, or somatosensory stimulation, delivered either alone or in concurrent pairs. Twenty young-adult participants were cued to attend to a single modality and detect targets in each trial. We found that NBR were consistently induced in all non-task-relevant primary sensory cortices and default mode regions during all stimuli. NBR were observed within the stimulated modality, in the cortex ipsilateral to the stimulus; as well as cross-modal responses bilaterally within the cortex of an unstimulated sensory modality. The NBR regions showed high spatial overlap with the primary sensory positive BOLD response (PBR) of the stimulated modality. The NBR occurred in spatially comparable regions across different modality stimuli such that the peak voxel location and spatial extent were comparable between within and cross-modal NBRs. Some specific differences were seen, such as stronger magnitude sensorimotor NBR to somatosensory stimuli than to visual or auditory. No significant relationships were found between subjects' PBR and NBR magnitude, but significant linear correlations were observed between NBRs indicating that subjects with high magnitude NBR within one sensory modality also displayed high magnitude cross-modal NBR in a different modality. These findings suggest that cortical NBR are largely consistent between different sensory stimuli but also contain stimulus-specific variability in magnitude and spatial extent. Finally, positive BOLD responses were stronger to dual stimuli in all contralateral primary sensory regions, whilst NBR were slightly increased in specific regions of ipsilateral visual and sensorimotor cortex. This finding suggests a strong contribution to NBR from bottom-up stimulus input that was further modulated by attention during dual conditions and that NBR is driven by a combination of bottom-up and top-down influences whereby contributions to its generation arise from both feed-forward signals from subcortical or activated sensory regions and feedback mechanisms such as higher-level attentional control.

Emotion Induction Modulates Neural Dynamics Related to the Originality of Ideational Creativity

Emotions remarkably impact our creative minds; nevertheless, a comprehensive mapping of their underlying neural mechanisms remains elusive. Therefore, we examined the influence of emotion induction on ideational originality and its associated neural dynamics. Participants were randomly presented with three short videos with sad, neutral, and happy content. After each video, ideational originality was evaluated using the alternate uses task. Both happy and sad inductions significantly enhanced ideational originality relative to the neutral induction condition. However, no significant difference was observed in ideational originality between the happy and sad emotion inductions. Associated neural dynamics were assessed through EEG time-frequency (TF) power and phase-amplitude coupling (PAC) analyses. Our findings suggest that emotional states elicit distinct TF and PAC profiles associated with ideational originality. Relative to baseline, gamma activity was enhanced after the neutral induction and more enhanced after the induction of a happy emotion but reduced after the induction of sad emotion 2-4 s after starting the task. Our functional connectivity couplings suggest that inducing happy and sad emotions may influence the working memory and attentional system differently, leading to varying effects on associated processing modes. Inducing a happy emotion may result in decreased neural activity and processing of rich information in working memory for exploring more original ideas through cognitive flexibility. In contrast, inducing a sad emotion may enhance neural activity and increase coupling within the attention system to exploit and select fewer original ideas through cognitive persistence.

High-Frequency rTMS Improves Visual Working Memory in Patients With aMCI: A Cognitive Neural Mechanism Study

BACKGROUND

Visual working memory (VWM), which is an essential component of higher cognitive processes, declines with age and is associated with the progression from amnestic mild cognitive impairment (aMCI) to Alzheimer's disease (AD). Cognitive impairment, particularly in VWM, is prominent in aMCI and may indicate disease progression. This study investigates the cognitive neural mechanisms responsible for VWM impairment in aMCI, with a focus on identifying the VWM processing stages affected. The study targets the dorsolateral prefrontal cortex (DLPFC) for repetitive transcranial magnetic stimulation (rTMS) to investigate its influence on VWM in aMCI patients. The role of the DLPFC in the top-down control of VWM processing is central to understanding rTMS effects on the stages of information processing in aMCI-related VWM impairments.

METHODS

A 7-day rTMS intervention was performed in 25 aMCI patients and 15 healthy elderly controls to investigate its effects on VWM and cognitive functions. Tasks included VWM change detection, digital symbol transformation, and the Stroop task for attention and executive functions. EEG analyses consisting of ERP, ERSP, and functional connectivity (wPLI) were integrated. The first part of the study addressed the cognitive neural mechanism of VWM impairment in aMCI and differentiated the processing stages using EEG. The second part investigated the effects of rTMS on EEG processing at different VWM stages and revealed cognitive neural mechanisms that improve visual working memory in aMCI.

RESULTS

The results indicated a significant deterioration of VWM tasks in aMCI, especially in accuracy and memory capacity, with prolonged reaction time and increased duration of the Stroop task. In the VWM memory encoding phase, N2pc amplitude, α-oscillation in the parieto-occipital region, and θ-band synchronization in the frontoparietal connectivity decreased. Conversely, rTMS improved N2pc amplitude, α-oscillation, and θ-band synchronization, which correlated with improved frontoparietal connectivity, parieto-occipital α-oscillation, and attentional capacity.

CONCLUSIONS

Patients with aMCI experience significant deterioration in VWM function, particularly during the encoding phase. This deterioration manifests in reduced accuracy and capacity of memory performance, accompanied by a significant decrease in N2pc amplitude, alpha oscillations, and theta-band connectivity in frontoparietal and fronto-occipital brain regions. rTMS proves to be a promising intervention that improves VWM, attention, and executive functions. In particular, it supports attention during target selection by increasing N2pc amplitude during encoding, enhancing alpha oscillations for better suppression of irrelevant information, and increasing synchronization in frontoparietal and occipital functional connectivity, which ultimately improves visual working memory.

Enhanced Working Memory Representations for Rare Events

Rare events (oddballs) produce a variety of enhanced physiological responses relative to frequent events (standards), including the P3b component of the event-related potential (ERP) waveform. Previous research has suggested that the P3b is related to working memory, which implies that working memory representations will be enhanced for rare stimuli. To test this hypothesis, we devised a modified oddball paradigm where a target disk was presented at one of 16 different locations, which were divided into rare and frequent sets. Participants made a binary response on each trial to report whether the target appeared in the rare set or the frequent set. As expected, the P3b was much larger for stimuli appearing at a location within the rare set. We also included occasional probe trials in which the subject reported the exact location of the target. Accuracy was higher for rare than frequent locations. In addition, memory reports on rare trials were more accurate in participants with larger P3b amplitudes on rare trials (although reports were not more accurate for trials with larger P3b amplitudes within participants). We also applied multivariate pattern analysis to the ERP data to "decode" the remembered location of the target. Decoding accuracy was greater for locations within the rare set than for locations within the frequent set. We then replicated and extended our behavioral findings in a follow-up experiment. These behavioral and electrophysiological results demonstrate that although both frequent and rare events are stored in working memory, working memory performance is enhanced for rare oddball events.

Decoding the rhythmic representation and communication of visual contents

Rhythmic neural activity is considered essential for adaptively modulating responses in the visual system. In this opinion article we posit that visual brain rhythms also serve a key function in the representation and communication of visual contents. Collating a set of recent studies that used multivariate decoding methods on rhythmic brain signals, we highlight such rhythmic content representations in visual perception, imagery, and prediction. We argue that characterizing representations across frequency bands allows researchers to elegantly disentangle content transfer in feedforward and feedback directions. We further propose that alpha dynamics are central to content-specific feedback propagation in the visual system. We conclude that considering rhythmic content codes is pivotal for understanding information coding in vision and beyond.

Attentional Refreshing in Working Memory and Its Interplay with Long-term Memory: A Behavioral and Electroencephalographic Study

Despite the growing interest in the study of attentional refreshing, the functioning of this working memory maintenance mechanism, including its cerebral underpinnings, is still debated. In particular, it remains unclear whether refreshing promotes long-term memory and whether it, in return, depends on long-term memory content to operate. Here, we used direct maintenance instructions and measured brain activity to investigate working memory maintenance with two objectives: (1) test if different behavioral and oscillatory patterns could be observed when participants were instructed to use attentional refreshing versus verbal rehearsal, and (2) observe whether and how refreshing is modulated when maintaining novel (pseudowords) versus familiar (words) memoranda. We conducted an EEG experiment using a modified Brown-Peterson task, in which we manipulated the type of maintenance engaged through explicit instructions (verbal rehearsal vs. refreshing), the type of memoranda (words vs. pseudowords), and the memory load (2 vs. 6). Using scalp EEG, we measured both neural oscillations during working memory maintenance and ERPs during the concurrent parity judgment task. For words, we showed that verbal rehearsal benefited more short-term recall whereas refreshing benefited more delayed recall. In keeping with these behavioral differences between maintenance instructions, frontal-midline theta power increased with memory load only when using verbal rehearsal, whereas occipito-parietal alpha desynchronization was larger with refreshing than verbal rehearsal. When maintaining pseudowords, verbal rehearsal also benefitted short-term recall more than refreshing. However, no long-term memory benefit of refreshing was observed for pseudowords, and oscillatory activity was not different under the two maintenance instructions. Our results provide new evidence supporting the independence between attentional refreshing and verbal rehearsal, and bring new insight into refreshing functioning. We discuss the possible interpretations of these results and the implications for the attentional refreshing literature.

Distractor-specific control adaptation in multidimensional environments

Goal-directed behaviour requires humans to constantly manage and switch between multiple, independent and conflicting sources of information. Conventional cognitive control tasks, however, only feature one task and one source of distraction. Therefore, it is unclear how control is allocated in multidimensional environments. To address this question, we developed a multidimensional task-set interference paradigm, in which people need to manage distraction from three independent dimensions. We use this task to test whether people adapt to previous conflict by enhancing task-relevant information or suppressing task-irrelevant information. Three experiments provided strong evidence for the latter hypothesis. Moreover, control adaptation was highly dimension specific. Conflict from a given dimension only affected processing of that same dimension on subsequent trials, with no evidence for generalization. A new neural network model shows that our results can only be simulated when including multiple independent conflict-detector units. Our results call for an update to classic models of cognitive control and their neurocomputational underpinnings.

Predicted action-effects shape action representation through pre-activation of alpha oscillations

Actions are typically accompanied by sensory feedback (or action-effects). Action-effects, in turn, influence the action. Theoretical accounts of action control assume a pre-activation of action-effects prior to action execution. Here we show that when participants were asked to report the time of their voluntary keypress using the position of a fast-rotating clock hand, a predictable action-effect (i.e. a 250 ms delayed sound after keypress) led to a shift of visuospatial attention towards the clock hand position of action-effect onset, thus demonstrating an influence of action-effects on action representation. Importantly, the attention shift occurred about 1 second before the action execution, which was further preceded and predicted by a lateralisation of alpha oscillations in the visual cortex. Our results indicate that when the spatial location is the key feature of action-effects, the neural implementation of the action-effect pre-activation is achieved through alpha lateralisation.

Age-related changes in neural oscillations vary as a function of brain region and frequency band

Advanced aging is associated with robust changes in neural activity. In addition to the well-established age-related slowing of the peak alpha frequency, there is a growing body of evidence showing that older age is also associated with changes in alpha power and beta power. Despite the important progress that has been made, the interacting effects of age and frequency band have not been directly tested in sensor and source space while controlling for aperiodic components. In the current study we address these limitations. We recruited 54 healthy younger and older adults and measured neural oscillations using a high-density electroencephalogram (EEG) system during resting-state with eyes closed. After preprocessing the EEG data and controlling for aperiodic components, we computed alpha and beta power in both sensor and source space. Permutation two-way ANOVAs between frequency band and age group were performed across all electrodes and across all dipoles. Our findings revealed significant interactions in sensorimotor, parietal, and occipital regions. The pattern driving the interaction varied across regions, with older age associated with a progressive decrease in alpha power and a progressive increase in beta power from parietal to sensorimotor regions. Our findings demonstrate that age-related changes in neural oscillations vary as a function of brain region and frequency band. We interpret our findings in the context of clinical and preclinical evidence of age effects on the cholinergic circuit and the Cortico-Basal Ganglia-Thalamo-Cortical (CBGTC) circuit.

Psychophysiological Effects of Left-Hand Contractions on Golf-Putting and Dart-Throwing Performance

Left-hand contractions (LHCs) are considered a useful technique to facilitate athletic performance under pressure by inhibiting conscious motor control through the induction of hemispheric brain asymmetry. However, the underlying mechanisms of LHCs remain unclear. Two experiments were conducted: novice golfers (30 participants) and dart players (40 participants) completed tasks while their cortical, muscle, and cardiac activities and kinematics were recorded. Performance was measured as the distance from the target. In Study 1 (golfers), no differences in performance were observed; however, LHCs reduced the electromyography signals in the left forearm during golf putting. In Study 2 (dart players), performance did not differ between study groups. Although right-dominant hemispheric asymmetry was induced by LHCs, it may not have facilitated golf-putting and dart-throwing performances. As LHCs induced asymmetry only around the central and parietal sites, we cast doubt on the idea that LHCs inhibit the conscious processing of movements due to left-temporal activation.

Reduced temporal variability of cortical excitation/inhibition ratio in schizophrenia

Altered neural excitation/inhibition (E/I) balance has long been suspected as a potential underlying cause for clinical symptoms in schizophrenia (SZ). Recent methodological advancements linking the spectral slope (β) of neurophysiological recordings - such as them electroencephalogram (EEG) - to E/I ratio provided much-needed tools to better understand this plausible relationship. Importantly, most approaches treat E/I ratio as a stationary feature in a single scaling range. On the other hand, previous research indicates that this property might change over time, as well as it can express different characteristics in low- and high-frequency regimes. In line, in this study we analyzed resting-state EEG recordings from 30 patients with SZ and 31 healthy controls (HC) and characterized E/I ratio via β separately for low- (1-4 Hz) and high- (20-45 Hz) frequency regimes in a time-resolved manner. Results from this analysis confirmed the bimodal nature of power spectra in both HC and SZ, with steeper spectral slopes in the high- compared to low-frequency ranges. We did not observe any between-group differences in stationary (i.e., time-averaged) neural signatures, however, the temporal variance of β in the 20-45 Hz regime was significantly reduced in SZ patients when compared to HC, predominantly over regions corresponding to the dorsal attention network. Furthermore, this alteration was found correlated to positive clinical symptom scores. Our study indicates that altered E/I ratio dynamics are a characteristic trait of SZ that reflect pathophysiological processes involving the parietal and occipital cortices, potentially responsible for some of the clinical features of the disorder.

Dissociating the roles of alpha oscillation sub-bands in visual working memory

Alpha oscillations play a critical role in visual working memory (VWM), but the specific contributions of lower and upper alpha sub-bands remain unclear. To address this, we employed a whole-field change detection paradigm to investigate how alpha power modulation and decoding accuracy differ between these sub-bands in response to varying set sizes and spatial extents of memory arrays. Our results revealed that lower alpha (8-9 Hz) exhibits widespread event-related desynchronization (ERD) during the early maintenance phase, which increases with set size and reflects attentional allocation to individual memory items. In contrast, upper alpha (10-12 Hz) demonstrates posteriorly localized ERD that is strongly associated with the spatial extent of memory arrays. During the late maintenance phase, upper alpha transitions to event-related synchronization (ERS), suggesting a role in suppression of irrelevant sensory inputs and enhancement of alertness. Multivariate decoding analyses showed that all alpha sub-bands accurately decoded both set size and spatial extent across time windows, with lower alpha achieving better decoding performance during the early maintenance phase and upper alpha excelling in later stages. These findings suggest that alpha oscillations encode both the number and spatial distribution of memory items, with lower and upper alpha sub-bands serving complementary roles in encoding and maintaining VWM representations.

Supportive but biased: Perceptual neural intergroup bias is sensitive to minor reservations about supporting outgroup immigration

While decreasing negative attitudes against outgroups are often reported by individuals themselves, biased behaviour prevails. This gap between words and actions may stem from unobtrusive mental processes that could be uncovered by using neuroimaging in addition to self-reports. In this study we investigated whether adding neuroimaging to a traditional intergroup bias measure could detect intersubject differences in intergroup bias processes in a societal context where opposing discrimination is normative. In a sample of 43 Finnish students, implicit behavioural measures failed to indicate intergroup bias against Middle Eastern and Muslim immigrants, and explicit measures reported rather positive attitudes and sentiments towards that targeted group. Yet, while implementing a repeatedly validated method for detecting intergroup bias, an implicit association paradigm presenting stereotypical ingroup and outgroup face stimuli while undergoing magnetoencephalography, we detected a clear neural difference between two experimental conditions. The neural effect is thought to reflect intergroup bias in the valence of the associations that faces evoke. The activity cluster of the neural bias peaked in BA37 and included significant activity in the fusiform gyrus, which has been repeatedly found to be active during face perception bias. Importantly, this neural pattern was driven by participants who were explicitly favourable of immigration - but to a lesser extent than others. These findings suggest that such variations in explicit support of immigration are associated with the differential neural sensitivity to the congruency of associations between intergroup faces and valence. This research showcases the potential of neuroimaging to unravel covert perceptual bias against outgroup members and its sensitivity to small variations in explicit attitudes.

Speech outcomes in cochlear implant users depend on visual cross-modal cortical activity measured before or after implantation

Cochlear implants can partially restore hearing function in deaf individuals, but long-term speech listening outcomes vary widely across cochlear implant users. Visual cross-modal plasticity, where auditory cortical neurons upregulate visual inputs to assist visual processing, is one factor proposed to worsen cochlear implant users' speech outcomes because it may limit auditory processing capability. However, evidence for this view is conflicting, and the relationship of cross-modal activity to speech perception may depend on other variables such as the type of visual activity and when it is assessed. To clarify, we measured visual cross-modal activity during a silent lip reading task using EEG in a cross-sectional, observational study. The study tested visual brain activation in 14 individuals prior to receiving a cochlear implant, 15 individuals tested at least 1 year after receiving and using a cochlear implant and 13 typical hearing controls who did not use a cochlear implant or hearing aid. Cross-modal responses to the onset of a visual event were positively correlated to speech outcomes in cochlear implant users tested after surgery but were negatively correlated in those tested prior to cochlear implant surgery. In addition, cross-modal increases in neural oscillatory power in the alpha band (8-12 Hz) arising in the lip reading task were associated with worse speech outcomes in both cochlear implant user groups. Taken together, results redress claims that cross-modal plasticity is maladaptive for speech outcomes and instead suggest that this relationship depends on the time point of testing, stage of sensory processing and likely the relevance of the stimulus for speech. In addition, findings form the basis for new neural markers that are predictive of cochlear implant users' long-term speech ability.

Dynamic changes in large-scale functional connectivity prior to stimulation determine performance in a multisensory task

Complex behavior and task execution require fast changes of local activity and functional connectivity in cortical networks at multiple scales. The roles that changes of power and connectivity play during these processes are still not well understood. Here, we study how fluctuations of functional cortical coupling across different brain areas determine performance in an audiovisual, lateralized detection task in the ferret. We hypothesized that dynamic variations in the network's state determine the animals' performance. We evaluated these by quantifying changes of local power and of phase coupling across visual, auditory and parietal regions. While power for hit and miss trials showed significant differences only during stimulus and response onset, phase coupling already differed before stimulus onset. An analysis of principal components in coupling at the single-trial level during this period allowed us to reveal the subnetworks that most strongly determined performance. Whereas higher global phase coupling of visual and auditory regions to parietal cortex was predictive of task performance, a second component revealed a reduction in coupling between subnetworks of different sensory modalities, probably to allow a better detection of the unimodal signals. Furthermore, we observed that long-range coupling became more predominant during the task period compared to the pre-stimulus baseline. Taken together, our results show that fluctuations in the network state, as reflected in large-scale coupling, are key determinants of the animals' behavior.

A Case Study on Neural Activity Characteristics in a Shooting Competition

Background: Sexual characteristics in brain neurophysiological activity are a significant area of research in cognitive neuroscience. As a sport that involves minimal physical movement, shooters remain largely stationary during aiming, facilitating the collection of their neural activity compared to athletes in other sports. Objectives: To investigate the neural characteristics of novice shooters of different genders under competitive conditions. Methods: Sixteen subjects participated in a shooting competition following four weeks of training. Electroencephalogram (EEG) data and behavioral data (shooting scores, aiming curves, and pressure curves) were recorded during the competition, and the power spectral density (PSD) and phase-locking value (PLV) network features were extracted to explore further the correlation between the shooting scores and neural activity. Results: In our sample, (1) there were no significant differences in shooting scores between males and females; (2) there were differences in PSD values across the theta, alpha, alpha-2, beta, and gamma frequency bands between males and females; and (3) there were differences in PLV network properties in the theta, alpha, beta, and gamma frequency bands between males and females. Correlation analysis revealed associations between shooting scores and neural activity in male and female novices. Conclusions: The case study demonstrated that males and females exhibited different neural activity characteristics in the shooting competition, providing a foundation for further investigation into the sex differences in neural activity in shooting competition.

EEG during dynamic facial emotion processing reveals neural activity patterns associated with autistic traits in children

Altered brain connectivity and atypical neural oscillations have been observed in autism, yet their relationship with autistic traits in nonclinical populations remains underexplored. Here, we employ electroencephalography to examine functional connectivity, oscillatory power, and broadband aperiodic activity during a dynamic facial emotion processing task in 101 typically developing children aged 4 to 12 years. We investigate associations between these electrophysiological measures of brain dynamics and autistic traits as assessed by the Social Responsiveness Scale, 2nd Edition (SRS-2). Our results revealed that increased facial emotion processing-related connectivity across theta (4 to 7 Hz) and beta (13 to 30 Hz) frequencies correlated positively with higher SRS-2 scores, predominantly in right-lateralized (theta) and bilateral (beta) cortical networks. Additionally, a steeper 1/f-like aperiodic slope (spectral exponent) across fronto-central electrodes was associated with higher SRS-2 scores. Greater aperiodic-adjusted theta and alpha oscillatory power further correlated with both higher SRS-2 scores and steeper aperiodic slopes. These findings underscore important links between facial emotion processing-related brain dynamics and autistic traits in typically developing children. Future work could extend these findings to assess these electroencephalography-derived markers as potential mechanisms underlying behavioral difficulties in autism.

Similarities and differences between chronic primary pain and depression in brain activities: Evidence from resting-state microstates and auditory Oddball task

BACKGROUND

In 2019, the International Association for the Study of Pain introduced the concept of 'chronic primary pain (CPP)', characterized by persistent non-organic pain with emotional and functional abnormalities. Underdiagnosed and linked to depression, CPP has poorly understood neural characteristics. Electroencephalogram (EEG) microstates enable detailed examination of brain network dynamics at the millisecond level. Incorporating task-related EEG features offers a comprehensive neurophysiological signature of brain dysfunction, facilitating exploration of potential neural mechanisms.

METHODS

This study employed resting-state and task-related auditory Oddball EEG paradigm to evaluate 20 healthy controls, 20 patients with depression, and 20 patients with CPP. An 8-minute recording of resting-state EEG was conducted to identify four typical microstates (A-D). Additionally, power spectral density (PSD) features were examined during an auditory Oddball paradigm.

RESULTS

Both CPP and Major Depressive Disorder (MDD) patients exhibited reduced occurrence rate and transition probabilities of other microstates to microstate C during resting-state EEG. Furthermore, more pronounced increase in Gamma PSD was observed in the occipital region of CPP during the Oddball task. In CPP, both resting-state microstate C and task-related Gamma PSD correlated with pain and emotional indicators. Notably, microstate C occurrence positively correlated with occipital Gamma PSD in MDD.

CONCLUSION

Conclusively, both CPP and MDD display dynamic abnormalities within the salient network, closely associated with pain and depressive symptoms in CPP. Unlike MDD, CPPs' dynamic network changes appear unrelated to perceptual integration function, indicating differing microstate functional impacts. Combining resting-state microstates and Oddball tasks may offer a promising avenue for identifying potential biomarkers in objectively assessing chronic primary pain.