Event-related Coherence Research Articles

Hypergraph of Functional Connectivity Based on Event-Related Coherence: Magnetoencephalography Data Analysis

We construct hypergraphs to analyze functional brain connectivity, leveraging event-related coherence in magnetoencephalography (MEG) data during the visual perception of a flickering image. Principal network characteristics are computed for the delta, theta, alpha, beta, and gamma frequency ranges. Employing a coherence measure, a statistical estimate of correlation between signal pairs across frequencies, we generate an edge time series, depicting how an edge evolves over time. This forms the basis for constructing an edge-to-edge functional connectivity network. We emphasize hyperedges as connected components in an absolute-valued functional connectivity network. Our coherence-based hypergraph construction specifically addresses functional connectivity among four brain lobes in both hemispheres: frontal, parietal, temporal, and occipital. This approach enables a nuanced exploration of individual differences within diverse frequency bands, providing insights into the dynamic nature of brain connectivity during visual perception tasks. The results furnish compelling evidence supporting the hypothesis of cortico–cortical interactions occurring across varying scales. The derived hypergraph illustrates robust activation patterns in specific brain regions, indicative of their engagement across diverse cognitive contexts and different frequency bands. Our findings suggest potential integration or multifunctionality within the examined lobes, contributing valuable perspectives to our understanding of brain dynamics during visual perception.

Atypical Activation of Laryngeal Somatosensory-Motor Cortex During Vocalization in People With Unexplained Chronic Cough

Unexplained chronic cough is common and has substantial negative quality-of-life implications, yet its causes are not well understood. A better understanding of how peripheral and central neural processes contribute to chronic cough is essential for treatment design. To determine if people with chronic cough exhibit signs of abnormal neural processing over laryngeal sensorimotor cortex during voluntary laryngeal motor activity such as vocalization. This was a cross-sectional study of a convenience sample of participants with chronic cough and healthy participants. Testing was performed in an acoustically and electromagnetically shielded chamber. In a single visit, electroencephalographic (EEG) signals were recorded from participants with chronic cough and healthy participants during voice production. The chronic cough group participants presented with unexplained cough of 8 weeks or longer duration with prior medical evaluation including negative results of chest imaging. None of the participants had a history of any neurologic disease known to impair vocalization or swallowing. Data collection for the healthy control group occurred from February 2 to June 28, 2018, and for the chronic cough group, from November 22, 2021, to June 21, 2022. Data analysis was performed from May 1 to October 30, 2022. Participants with or without chronic cough. Event-related spectral perturbation over the laryngeal area of somatosensory-motor cortex from 0 to 30 Hz (ie, θ, α, and β bands) and event-related coherence as a measure of synchronous activity between somatosensory and motor cortical regions. The chronic cough group comprised 13 participants with chronic cough (mean [SD] age, 63.5 [7.8] years; 9 women and 4 men) and the control group, 10 healthy age-matched individuals (mean [SD] age, 60.3 [13.9] years; 6 women and 4 men). In the chronic cough group, the typical movement-related desynchronization over somatosensory-motor cortex during vocalization was significantly reduced across θ, α, and β frequency bands when compared with the control group. This cross-sectional study found that the typical movement-related suppression of brain oscillatory activity during vocalization is weak or absent in people with chronic cough. Thus, chronic cough affects sensorimotor cortical activity during the asymptomatic voluntary activation of laryngeal muscles.

Cortical Processing of Binaural Cues as Shown by EEG Responses to Random-Chord Stereograms

Spatial hearing facilitates the perceptual organization of complex soundscapes into accurate mental representations of sound sources in the environment. Yet, the role of binaural cues in auditory scene analysis (ASA) has received relatively little attention in recent neuroscientific studies employing novel, spectro-temporally complex stimuli. This may be because a stimulation paradigm that provides binaurally derived grouping cues of sufficient spectro-temporal complexity has not yet been established for neuroscientific ASA experiments. Random-chord stereograms (RCS) are a class of auditory stimuli that exploit spectro-temporal variations in the interaural envelope correlation of noise-like sounds with interaurally coherent fine structure; they evoke salient auditory percepts that emerge only under binaural listening. Here, our aim was to assess the usability of the RCS paradigm for indexing binaural processing in the human brain. To this end, we recorded EEG responses to RCS stimuli from 12 normal-hearing subjects. The stimuli consisted of an initial 3-s noise segment with interaurally uncorrelated envelopes, followed by another 3-s segment, where envelope correlation was modulated periodically according to the RCS paradigm. Modulations were applied either across the entire stimulus bandwidth (wideband stimuli) or in temporally shifting frequency bands (ripple stimulus). Event-related potentials and inter-trial phase coherence analyses of the EEG responses showed that the introduction of the 3- or 5-Hz wideband modulations produced a prominent change-onset complex and ongoing synchronized responses to the RCS modulations. In contrast, the ripple stimulus elicited a change-onset response but no response to ongoing RCS modulation. Frequency-domain analyses revealed increased spectral power at the fundamental frequency and the first harmonic of wideband RCS modulations. RCS stimulation yields robust EEG measures of binaurally driven auditory reorganization and has potential to provide a flexible stimulation paradigm suitable for isolating binaural effects in ASA experiments.

Event-Related Desynchronization and Corticomuscular Coherence Observed During Volitional Swallow by Electroencephalography Recordings in Humans.

Swallowing in humans involves many cortical areas although it is partly mediated by a series of brainstem reflexes. Cortical motor commands are sent to muscles during swallow. Previous works using magnetoencephalography showed event-related desynchronization (ERD) during swallow and corticomuscular coherence (CMC) during tongue movements in the bilateral sensorimotor and motor-related areas. However, there have been few analogous works that use electroencephalography (EEG). We investigated the ERD and CMC in the bilateral sensorimotor, premotor, and inferior prefrontal areas during volitional swallow by EEG recordings in 18 healthy human subjects. As a result, we found a significant ERD in the beta frequency band and CMC in the theta, alpha, and beta frequency bands during swallow in those cortical areas. These results suggest that EEG can detect the desynchronized activity and oscillatory interaction between the cortex and pharyngeal muscles in the bilateral sensorimotor, premotor, and inferior prefrontal areas during volitional swallow in humans.

Event-Related Coherence in Visual Cortex and Brain Noise: An MEG Study

The analysis of neurophysiological data using the two most widely used open-source MATLAB toolboxes, FieldTrip and Brainstorm, validates our hypothesis about the correlation between event-related coherence in the visual cortex and neuronal noise. The analyzed data were obtained from magnetoencephalography (MEG) experiments based on visual perception of flickering stimuli, in which fifteen subjects effectively participated. Before coherence and brain noise calculations, MEG data were first transformed from recorded channel data to brain source waveforms by solving the inverse problem. The inverse solution was obtained for a 2D cortical shape in Brainstorm and a 3D volume in FieldTrip. We found that stronger brain entrainment to the visual stimuli concurred with higher brain noise in both studies.

P07-F Event related EEG brain oscillations differentiate cognitive decline in patients with Parkinson’s disease

Background Studies on Event Related EEG Brain Oscillations presented essential results on the understanding of cognitive brain function and cognitive decline in different pathologies. Event related oscillatory dynamics in Parkinson’s disease (PD) have not been studied comprehensively. In the last three years, our group aimed to fulfill this critical gap. Material and methods 27 PD patients without cognitive deficits, 34 PD patients with Mild Cognitive Impairment, 22 patients with PD Dementia and 33 healthy controls were included in the study.EEG was recorded during visual and auditory oddball paradigEvent related power spectrum, phase locking, event related coherence were evaluated in delta, theta, alpha, beta and gamma frequency bands for all group of subjects. Results Event related delta, theta, alpha and beta power and phase locking increased with a cognitive load in healthy subjects but these responses decreased in PD patients who have mild cognitive impairment and dementia. Event related delta, theta, and alpha coherence values were also lower in PD patients with cognitive deficits. The most differentiated results were found in the theta frequency band, frontal theta responses were the lowest in PD patients with dementia especially during the visual paradigm rather than the auditory paradigm. Conclusions Comprehensive analysis of Event-related oscillatory dynamics could successfully differentiate the cognitive decline in Parkinson’s disease patients. The differentiation between subject groups did not just appear in local circuits, but long distance connections were also impaired in PD patients with cognitive decline. Acknowledgments This work (Grant No. 214S111 ) was supported by TUBITAK .

Functional Connectivity Pattern Analysis Underlying Neural Oscillation Synchronization during Deception.

To characterize system cognitive processes during deception, event-related coherence was computed to investigate the functional connectivity among brain regions underlying neural oscillation synchronization. In this study, 15 participants were randomly assigned to honesty or deception groups and were instructed to tell the truth or lie when facing certain stimuli. Meanwhile, event-related potential signals were recorded using a 64-channel electroencephalography cap. Event-related coherence was computed separately in four frequency bands (delta (1-3.5 Hz), theta (4-7 Hz), alpha (8-13 Hz), and beta (14-30 HZ)) for the long-range intrahemispheric electrode pairs (F3P3, F4P4, F3T7, F4T8, F3O1, and F4O2). The results indicated that deceptive responses elicited greater connectivities in the frontoparietal and frontotemporal networks than in the frontooccipital network. Furthermore, the deception group displayed lower values of coherence in the frontoparietal electrode pairs in the alpha and beta bands than the honesty group. In particular, increased coherence in the delta and theta bands on specific left frontoparietal electrode pairs was observed. Additionally, the deception group exhibited higher values of coherence in the delta band and lower values of coherence in the beta band on the frontotemporal electrode pairs than did the honesty group. These data indicated that the active cognitive processes during deception include changes in ensemble activities between the frontal and parietal/temporal regions.

Do scalp-recorded slow potentials during neuro-feedback training reflect the cortical activity?

ObjectiveNeuro-feedback (NFB) training by the self-regulation of slow potentials (SPs) <0.5 Hz recorded from the vertex scalp has been applied for seizure suppression in patients with epilepsy. However, SP is highly susceptible to artifact contamination, such as the galvanic skin response (GSR). This study aimed to evaluate the correlation between SPs recorded from the scalp and intracranial electroencephalography (EEG) by event-related coherence analysis. MethodsThe scalp and subdural SPs were simultaneously recorded during NFB training by the DC-EEG machine while undergoing invasive recordings before epilepsy surgery in 10 patients with refractory partial epilepsy. The SPs at the vertex electrode were used as a reference for coherence analysis. ResultsThe coherence of SPs negatively correlated with the distance between the subdural and scalp electrodes. A significant negative correlation was noted between the linear subdural–scalp electrode distance and the coherence value (r = − 0.916, p < 0.001). ConclusionScalp-recorded SPs from the vertex area primarily reflect the cortical activity of high lateral convexity. SignificanceOur results strongly suggest that SPs in NFB recorded from the vertex scalp electrode is derived from the cortices of high lateral convexity but not from the artifacts, such as GSR.

Study of target and non-target interplay in spatial attention task

Selective visual attention is the ability to selectively pay attention to the targets while inhibiting the distractors. This paper aims to study the targets and non-targets interplay in spatial attention task while subject attends to the target object present in one visual hemifield and ignores the distractor present in another visual hemifield. This paper performs the averaged evoked response potential (ERP) analysis and time-frequency analysis. ERP analysis agrees to the left hemisphere superiority over late potentials for the targets present in right visual hemifield. Time-frequency analysis performed suggests two parameters i.e. event-related spectral perturbation (ERSP) and inter-trial coherence (ITC). These parameters show the same properties for the target present in either of the visual hemifields but show the difference while comparing the activity corresponding to the targets and non-targets. In this way, this study helps to visualise the difference between targets present in the left and right visual hemifields and, also the targets and non-targets present in the left and right visual hemifields. These results could be utilised to monitor subjects’ performance in brain–computer interface (BCI) and neurorehabilitation.

Multifaceted pattern of neural efficiency in working memory capacity

The objective of the present study was to investigate whether neural efficiency can be observed in visual working memory performance. Thirty low- and thirty high-performers were selected from a larger cohort of students based on performance on a visual WM task. Electroencephalogram (EEG) data during performance on this task was analyzed with event-related desynchronization/synchronization (ERD/ERS) and event-related coherence (ErCoh) in individually determined theta, alpha, and gamma frequency bands. The results demonstrated that high-performers in comparison to low-performers showed significantly different brain oscillatory responses in all three cognitive processes identified in the WM task – encoding, maintenance and retrieval. High-performers displayed: (1) Increased alpha ERD during encoding and increased gamma ERD during encoding and maintenance, which did not depend on set size, as well as (2) increased theta band ErCoh in fronto-parietal networks during maintenance and retrieval. To some extent, neural efficiency was observed in the gamma frequency band (ERD) and in theta coherence (ErCoh). The results tentatively lend support to the continuous single resource model assuming that working memory capacity is a flexible resource that can be spread among all elements in the sensory input as opposed to the model of discrete slots.

Electroencephalographic connectivity measures predict learning of a motor sequencing task.

Individuals vary significantly with respect to rate and degree of improvement with motor practice. While the regions that underlie motor learning have been well described, neurophysiological factors underlying differences in response to motor practice are less well understood. The present study examined both resting-state and event-related EEG coherence measures of connectivity as predictors of response to motor practice on a motor sequencing task using the dominant hand. Thirty-two healthy young right-handed participants underwent resting EEG before motor practice. Response to practice was evaluated both across the single session of motor practice and 24 h later at a retention test of short-term motor learning. Behaviorally, the group demonstrated statistically significant gains both in single-session "motor improvement" and across-session "motor learning." A resting-state measure of whole brain coherence with primary motor cortex (M1) at baseline robustly predicted subsequent motor improvement (validated R2 = 0.55) and motor learning (validated R2 = 0.68) in separate partial least-squares regression models. Specifically, greater M1 coherence with left frontal-premotor cortex (PMC) at baseline was characteristic of individuals likely to demonstrate greater gains in both motor improvement and motor learning. Analysis of event-related coherence with respect to movement found the largest changes occurring in areas implicated in planning and preparation of movement, including PMC and frontal cortices. While event-related coherence provided a stronger prediction of practice-induced motor improvement (validated R2 = 0.73), it did not predict the degree of motor learning (validated R2 = 0.16). These results indicate that connectivity in the resting state is a better predictor of consolidated learning of motor skills. NEW & NOTEWORTHY Differences in response to motor training have significant societal implications across a lifetime of motor skill practice. By evaluating both resting-state and event-related measures of brain function, our findings highlight interindividual differences in brain connectivity providing unique insights into differences in response to motor training. These findings have wide-ranging implications in settings ranging from advanced professional motor training to rehabilitation after brain injury.

Affective pictures processing is reflected by an increased long-distance EEG connectivity.

Analysis of affective picture processing by means of EEG has invaded the literature. The methodology of event-related EEG coherence is one of the essential methods used to analyze functional connectivity. The aims of the present study are to find out the long range EEG connectivity changes in perception of different affective pictures and analyze gender differences in these long range connected networks. EEGs of 28 healthy subjects (14 female) were recorded at 32 locations. The participants passively viewed emotional pictures (IAPS, unpleasant, pleasant, neutral). The long-distance intra-hemispheric event-related coherence was analyzed for delta (1-3.5Hz), theta (4-7.5Hz), and alpha (8-13Hz) frequency ranges for F3-T7, F4-T8, F3-TP7, F4-TP8, F3-P3, F4-P4, F3-O1, F4-O2, C3-O1, C4-O2 electrode pairs. Unpleasant pictures elicited significantly higher delta coherence values than neutral pictures (p<0.05), over fronto-parietal, fronto-occipital, and centro-occipital electrode pairs. Furthermore, unpleasant pictures elicited higher theta coherence values than pleasant (p<0.05) and neutral pictures (p<0.05). The present study showed that female subjects had higher delta (p<0.05) and theta (p<0.05) coherence values than male subjects. This difference was observed more for emotional pictures than for neutral pictures. This study showed that the brain connectivity was higher during emotional pictures than neutral pictures. Females had higher connectivity between different parts of the brain than males during emotional processes. According to these results, we may comment that increased valence and arousal caused increased brain activity. It seems that not just single sources but functional networks were also activated during perception of emotional pictures.

Explore the Functional Connectivity between Brain Regions during a Chemistry Working Memory Task

Previous studies have rarely examined how temporal dynamic patterns, event-related coherence, and phase-locking are related to each other. This study assessed reaction-time-sorted spectral perturbation and event-related spectral perturbation in order to examine the temporal dynamic patterns in the frontal midline (F), central parietal (CP), and occipital (O) regions during a chemistry working memory task at theta, alpha, and beta frequencies. Furthermore, the functional connectivity between F-CP, CP-O, and F-O were assessed by component event-related coherence (ERCoh) and component phase-locking (PL) at different frequency bands. In addition, this study examined whether the temporal dynamic patterns are consistent with the functional connectivity patterns across different frequencies and time courses. Component ERCoh/PL measured the interactions between different independent components decomposed from the scalp EEG, mixtures of time courses of activities arising from different brain, and artifactual sources. The results indicate that the O and CP regions’ temporal dynamic patterns are similar to each other. Furthermore, pronounced component ERCoh/PL patterns were found to exist between the O and CP regions across each stimulus and probe presentation, in both theta and alpha frequencies. The consistent theta component ERCoh/PL between the F and O regions was found at the first stimulus and after probe presentation. These findings demonstrate that temporal dynamic patterns at different regions are in accordance with the functional connectivity patterns. Such coordinated and robust EEG temporal dynamics and component ERCoh/PL patterns suggest that these brain regions’ neurons work together both to induce similar event-related spectral perturbation and to synchronize or desynchronize simultaneously in order to swiftly accomplish a particular goal. The possible mechanisms for such distinct component phase-locking and coherence patterns were also further discussed.

Coupling in the cortico-basal ganglia circuit is aberrant in the ketamine model of schizophrenia

Recent studies have suggested the implication of the basal ganglia in the pathogenesis of schizophrenia. To investigate this hypothesis, here we have used the ketamine model of schizophrenia to determine the oscillatory abnormalities induced in the rat motor circuit of the basal ganglia. The activity of free moving rats was recorded in different structures of the cortico-basal ganglia circuit before and after an injection of a subanesthesic dose of ketamine (10mg/kg). Spectral estimates of the oscillatory activity, phase-amplitude cross-frequency coupling interactions (CFC) and imaginary event-related coherence together with animals׳ behavior were analyzed. Oscillatory patterns in the cortico-basal ganglia circuit were highly altered by the effect of ketamine. CFC between the phases of low-frequency activities (delta, 1–4; theta 4–8Hz) and the amplitude of high-gamma (~80Hz) and high-frequency oscillations (HFO) (~150Hz) increased dramatically and correlated with the movement increment shown by the animals. Between-structure analyses revealed that ketamine had also a massive effect in the low-frequency mediated synchronization of the HFO’s across the whole circuit. Our findings suggest that ketamine administration results in an aberrant hypersynchronization of the whole cortico-basal circuit where the tandem theta/HFO seems to act as the main actor in the hyperlocomotion shown by the animals. Here we stress the importance of the basal ganglia circuitry in the ketamine model of schizophrenia and leave the door open to further investigations devoted to elucidate to what extent these abnormalities also reflect the prominent neurophysiological deficits observed in schizophrenic patients.

A Link between the Increase in Electroencephalographic Coherence and Performance Improvement in Operating a Brain-Computer Interface.

We study the relationship between electroencephalographic (EEG) coherence and accuracy in operating a brain-computer interface (BCI). In our case, the BCI is controlled through motor imagery. Hence, a number of volunteers were trained using different training paradigms: classical visual feedback, auditory stimulation, and functional electrical stimulation (FES). After each training session, the volunteers' accuracy in operating the BCI was assessed, and the event-related coherence (ErCoh) was calculated for all possible combinations of pairs of EEG sensors. After at least four training sessions, we searched for significant differences in accuracy and ErCoh using one-way analysis of variance (ANOVA) and multiple comparison tests. Our results show that there exists a high correlation between an increase in ErCoh and performance improvement, and this effect is mainly localized in the centrofrontal and centroparietal brain regions for the case of our motor imagery task. This result has a direct implication with the development of new techniques to evaluate BCI performance and the process of selecting a feedback modality that better enhances the volunteer's capacity to operate a BCI system.

Time-Frequency Bands of Electromagnetic Wave from ERPCOH on Developmental Changes

Recent changes in ongoing background activity are one of the most popular approaches to investigate brain activity for understanding child development. However, research using event-related responses of cortico-cortical connections to explore changes during childhood is rare. This study investigates mature changes in brain connectivity in associative reorganization patterns and hypothesizes that age-related changes affect oscillatory connections. The sample included children aged 7 years, 11 years, and adults. The 3 groups were studied in the time-frequency domain to analyze event-related cross phase coherence (ERPCOH) between different parts of the brain as they performed an auditory oddball task. Compared to the adult participants, the 11-year-old participants were found to have increased connectivity in theta (4-7 Hz), beta-2 (20-30 Hz), and gamma bands (30-50 Hz) in the early component (N1, 80-140 ms), although ERPCOH value decreased in the alpha-1 (7-10 Hz) and alpha-2 bands (10-13 Hz). Compared to the 11-year-old participants, 7-year-old participants had greater connectivity decreases in all frequency bands, most significantly in theta, beta-2, and gamma bands.

P 158. Neural correlates of Hebbian and anti-hebbian spike-timing-dependent plasticity in human: A TMS–EEG combined study

Introduction In a recent work by our group we used transcranial magnetic stimulation (TMS) to repeatedly activate the connection between the posterior parietal cortex (PPC) and the primary motor cortex (M1) of the left dominant hemisphere with a paired associative stimulation (PAS) protocol. By varying inter-pulse interval and the activation of different M1 neuronal populations we were able to induce LTP or LTD-like effects as indexed by Motor Evoked Potentials (MEPs) amplitude modulation that followed either Hebbian or anti-Hebbian temporal rules. Objectives Our aim was to further investigate the effects induced by this cortico-cortical PAS protocol over EEG activity, by means of a TMS–EEG coregistration approach. Materials and methods 13 volunteers underwent our novel PAS protocol. Paired stimuli were applied with PPC-TMS preceding (+5 ms) or following (−5 ms) M1 stimulation. In a third condition, the induced current direction over M1 was changed from postero–anterior (PA) to antero–posterior (AP) and the ISI was set at +5 ms. Eighty single pulse TMS were applied to M1 before and after PAS while continuously acquiring EEG from 21 electrodes and recording MEPs from the first dorsal interosseous muscle. We then analysed (i) functional coupling though event-related coherence (ERcoh) for alpha (8–12 Hz) and beta (13–30 Hz) band, (ii) changes in M1 reactivity through TMS-Evoked Potentials (TEPs) and (iii) MEPs amplitude. Results When PPC preceded M1PA stimulation (+5 ms) MEPs amplitude significantly decreased ( p = 0.001), while there was a concurrent increase in ERcoh for the beta band, topographically restricted to P3–C3 pair ( p = 0.02), representing the closest electrodes to the stimulated regions. TEPs analysis indicated a decrease of those components forming a dipole over left centro-parietal sites peaking at about 13 and 20 ms. When PPC followed M1PA stimulation (−5 ms) an increase in MEPs amplitude was induced (p = 0.01) with a concurrent ERcoh increase in the alpha band for P3–C3 pair ( p = 0.01). TEPs component were again modulated at 13 and 20 ms, with an increased amplitude after PAS administration. The AP condition led to opposite results: an increased MEP amplitude when PPC preceded M1AP stimulation (p). Conclusions These findings shed new light on the cortical mechanisms underlying antithetic learning rules in humans. We found that both post-synaptic long term potentiation or depression are always associated to an increased functional connectivity that exclusively upsurge between the stimulated areas. However, the sign of cortical plasticity in M1 is indexed by different brain oscillation activities in the alpha and beta bands. Finally distinct plastic changes differently modulate M1 reactivity as indexed by opposite changes of TEPs amplitude.

EEG coherence during mental rotation of letters, hands and scenes

The purpose of the present study was to investigate differences in the electrocortical synchronization pattern during mental rotation of three different object categories as well as six different rotation angles. Therefore, event-related coherence of the electroencephalographic (EEG) activity between selective frontal and parietal electrode pairs of ten subjects was measured during the performance of a mental rotation task consisting of rotation of letters, hands and scenes. Statistical analysis showed an increased coherence of frontal and parietal electrode pairs for the condition LETTER in comparison to the other conditions in the alpha1- (8.5–10Hz) and alpha2-band (10, 5–12Hz) supporting the notion of different mental rotation mechanisms for externally and internally represented objects. Additionally decreased coherence of the frontal and parietal electrode pairs was found for the rotation angles 30° to 150° in comparison to the 0° and 180° rotations for the alpha1- and alpha2-band as well as the gamma frequency band (30–45Hz). It is assumed that this decrease of synchronization reflects the mental rotation process implying that the mental rotation process of 180° differs from the rotation process of all other rotation angles.

A comparative study of auditory and visual event related coherences

The analysis of evoked and event related EEG Coherence gives important information on EEG changes in long distance connections in brain areas upon application of sensory/cognitive stimulations. The comparison of evoked/event related coherences of healthy subjects versus coherences in neuropsychiatric patients could be a new emerging method to understand brain pathologies. At the first step analyzes of evoked/event related coherences in healthy subjects are needed. The present study aims to fulfill this gap in the literature. 27 healthy subjects were included in this study. Simple visual and auditory stimulation and visual /auditory oddball paradigms were presented to the subjects during EEG recording. The coherence was analyzed for delta (1-3.5 Hz), theta (4-7.8 Hz), alpha (8-13.7 Hz), beta (14.6-30 Hz) and gamma (30-48 Hz) frequency ranges for (F3P3, F4-P4, F3-T7, F4-T8, F3-TP7, F4-TP8, F3-O1, F4-O2, C3-O1, C4-O2) electrode pairs. The repeated measures of ANOVA were used for statistical analysis. Event related delta, theta, alpha target coherence values were higher in the range of 25% -70% than the event related delta, theta, alpha non-target coherence values and as well evoked coherence values in both auditory and visual paradigms (pb0.05). No significant differences were recorded between target-nontarget and evoked coherence values in beta and gamma frequency ranges (pb0.05). Furthermore, evoked and event related coherence values in response to visual stimuli were higher than the evoked and event related coherence values in response to auditory stimuli (pb0.05). The results showed the existence of separate sensory and cognitive networks that are activated either on sensory or cognitive stimulation. These results may, in turn, serve in future to accomplish a more differentiated analysis in neuropsychiatric patients.

EEG correlates of haptic feedback in a visuomotor tracking task

This study investigates the temporal brain dynamics associated with haptic feedback in a visuomotor tracking task. Haptic feedback with deviation-related forces was used throughout tracking experiments in which subjects' behavioral responses and electroencephalogram (EEG) data were simultaneously measured. Independent component analysis was employed to decompose the acquired EEG signals into temporally independent time courses arising from distinct brain sources. Clustering analysis was used to extract independent components that were comparable across participants. The resultant independent brain processes were further analyzed via time–frequency analysis (event-related spectral perturbation) and event-related coherence (ERCOH) to contrast brain activity during tracking experiments with or without haptic feedback. Across subjects, in epochs with haptic feedback, components with equivalent dipoles in or near the right motor region exhibited greater alpha band power suppression. Components with equivalent dipoles in or near the left frontal, central, left motor, right motor, and parietal regions exhibited greater beta-band power suppression, while components with equivalent dipoles in or near the left frontal, left motor, and right motor regions showed greater gamma-band power suppression relative to non-haptic conditions. In contrast, the right occipital component cluster exhibited less beta-band power suppression in epochs with haptic feedback compared to non-haptic conditions. The results of ERCOH analysis of the six component clusters showed that there were significant increases in coherence between different brain networks in response to haptic feedback relative to the coherence observed when haptic feedback was not present. The results of this study provide novel insight into the effects of haptic feedback on the brain and may aid the development of new tools to facilitate the learning of motor skills.