Early Event-related Potentials Research Articles

Fast acquisition of full-range auditory event-related potentials using an interleaved deconvolution approach.

This work relates to recent advances in the field of auditory event-related potentials (ERP), specifically deconvolution-based ERP acquisition and single-trial processing. An efficient stimulus sequence optimization method for ERP deconvolution is proposed, achieving consistent noise attenuation within a broad designated frequency range. Furthermore, a stimulus presentation paradigm for the fast, interleaved acquisition of auditory brainstem, middle-latency and late responses featuring alternating periods of high-rate deconvolution sequences, and subsequent low-rate stimulation is investigated in 20 normal hearing subjects. Deconvolved sequence responses containing early and middle-latency ERP components are fused with subsequent late responses using a time-frequency resolved weighted averaging method based on cross-trial regularity, yielding a uniform signal-to-noise ratio of the full-range auditory ERP across investigated timescales. Obtained average ERP waveforms exhibit morphologies consistent with both literature values and reference recordings acquired in 15 normal hearing subjects using a prior art approach to full-range auditory ERP acquisition, with all prominent waves being visible in the grand average waveforms. Results suggest the proposed interleaved stimulus presentation and associated ERP processing methodology to be suitable for the fast, reliable extraction of full-range auditory processing correlates in future ERP studies.

Sequential conflict resolution under multiple concurrent conflicts: An ERP study

The purpose of the present study was to determine whether responding to multiple concurrent conflicts results in a simultaneous or sequential conflict resolution. To this end, we measured event-related potentials (ERPs) in a paradigm combining a Stroop and a flanker task. In this paradigm, participants were asked to respond to the color of the central letter while ignoring the meaning of the word (Stroop task) and the color of the flanking letters (flanker task). Trials were either incongruent (i.e., inducing a conflict between two response alternatives) or congruent (i.e., inducing no response conflict) in both tasks, or incongruent in one task and congruent in the other task. The behavioral results showed a smaller Stroop congruency effect (i.e., a smaller difference between Stroop incongruent and congruent trials) for flanker incongruent than for flanker congruent trials, replicating previous findings. The ERP results showed that an early ERP component (i.e., P2) was associated with the resolution of the flanker conflict, whereas a later component (i.e., N450) was associated with the resolution of the Stroop conflict. Together, these findings emphasize a sequential organization of conflict resolution processes in the brain which is adaptive when facing multiple concurrent conflicts.

Learning to see the threat: temporal dynamics of ERPs of motivated attention in fear conditioning.

Social threat detection is important in everyday life. Studies of cortical activity have shown that event-related potentials (ERPs) of motivated attention are modulated during fear conditioning. The time course of motivated attention in learning and extinction of fear is, however, still largely unknown. We aimed to study temporal dynamics of learning processes in classical fear conditioning to social cues (neutral faces) by selecting an experimental setup that produces large effects on well-studied ERP components (early posterior negativity, EPN; late positive potential, LPP; stimulus preceding negativity, SPN) and then exploring small consecutive groups of trials. EPN, LPP, and SPN markedly and quickly increased during the acquisition phase in response to the CS+ but not the CS−. These changes were visible even at high temporal resolution and vanished completely during extinction. Moreover, some evidence was found for component differences in extinction learning, with differences between CS+ and CS− extinguishing faster for late as compared to early ERP components. Results demonstrate that fear learning to social cues is a very fast and highly plastic process and conceptually different ERPs of motivated attention are sensitive to these changes at high temporal resolution, pointing to specific neurocognitive and affective processes of social fear learning.

Racialized images: Tracing appraisals of police force and protest.

As race acts as a social frame of reference, it should guide individual's appraisal of visual representations of social events and issues. Thus, grounded in Scherer's (2009) model of appraisal as a sequential process, in 2 experiments (N = 133, 166) we used early event-related potentials (ERPs) of brain activity (the N100, P200, P300) to examine Black and White participants' appraisals of the novelty of images of police force against Black (and White) targets, as well as of Black-led protest. We used a later ERP (the late positive potential, LPP) as well as blood pressure to assess their appraisal of motivational relevance, and self-reported affect and emotion to assess conscious experience. White participants' early ERPs suggested that they appraised the images as more novel than did Black participants. Nevertheless, Black participants' later (LPP) ERP, and blood pressure, suggested that they appraised the images as more motivationally relevant. Consistent with this, Black participants expressed more attentiveness, anger, and empowerment at the images, whereas White participants expressed more surprise. A mediation model in Experiment 2 showed that self-reported familiarity with past racial violence, as well as surprise and attentiveness to the images, explained the difference between Black and White participants' appraisals of motivational relevance (i.e., the LPP). We discuss implications for appraisal theory, stress and coping, and societally situated cognition and affect. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Temporal dynamics of audiovisual affective processing

This study used event-related potentials (ERPs) to investigate the time course of auditory, visual, and audiovisual affective processing. Stimuli consisted of naturalistic silent videos, instrumental music clips, or combination of the two, with valence varied at three levels for each modality and arousal matched across valence conditions. Affective ratings of the unimodal and multimodal stimuli showed evidence of visual dominance, congruency, and negativity dominance effects. ERP results for unimodal presentations revealed valence effects in early components for both modalities, but only for the visual condition in a late positive potential. The ERP results for multimodal presentations showed effects for both visual valence and auditory valence in three components, early N200, P300 and LPP. A modeling analysis of the N200 component suggested its role in the visual dominance effect, which was further supported by a correlation between behavioral visual dominance scores and the early ERP components. Significant congruency comparisons were also found for N200 amplitudes, suggesting that congruency effects may occur early. Consistent differences between negative and positive valence were found for both visual and auditory modalities in the P300 at anterior electrode clusters, suggesting a potential source for the negativity dominance effect observed behaviorally. The separation between negative and positive valence also occurred at LPP for the visual modality. Significant auditory valence modulation was found for the LPP, implying an integration effect in which valence sensitivity of the LPP emerged for the audiovisual condition. These results provide a basis for mapping out the temporal dynamics of audiovisual affective processing.

Direct Electrophysiological Mapping of Shape-Induced Affective Perception.

Visual information may convey different affective valences and induce our brain into different affective perceptions. Many studies have found that unpleasant stimuli could produce stronger emotional effects than pleasant stimuli could. Although there has been a notion that triangle is perceived as negative and circle as positive, there has been no systematic study to map the degrees of valence of shapes with different affective perceptions. Here, we employed four shapes (ellipse, triangle, and line-drawn happy and angry faces) to investigate the behavior and electrophysiological responses, in order to systematically study shape-induced affective perception. The reaction time delay and the event-related potential (ERP), particularly the early ERP component, were applied to find the associations with different affective perceptions. Our behavioral results showed that reaction time for angry face was significantly shorter than those for the other three types of stimuli (p < 0.05). In the ERP results, P1, N1, P2, and N2 amplitudes for angry face were significantly larger than those for happy face. Similarly, P1, N1, P2, and N2 amplitudes for triangle were significantly larger than those for ellipse. Particularly, P1 amplitude in the parietal lobe for angry face was the strongest, followed by happy face, triangle, and ellipse. Hence, this work found distinct electrophysiological evidence to map the shape-induced affective perception. It supports the hypothesis that affective strain would induce larger amplitude than affective ease does and strong affective stimuli induce larger amplitude than mild affective stimuli do.

Study of image quality using event-related potentials measurement

The image quality was studied using event-related potentials (ERPs), behavioral data, and psychological measurement. In our experiment, different quality images were obtained by changing σ values in the Gaussian kernel function. The results showed that measurable ERPs, behavioral data, and psychological parameters varied with the change in the image quality. The more impaired image elicited the higher and earlier ERPs components over all scalp areas. Meanwhile, the response time reduced and detection rate increased with an increase in the blurriness level σ. The P300 and N200 components of different scalp areas elicited by different image qualities were analyzed. The N200 amplitude and P300 latency over the anterior scalp region were stronger and shorter than the ones over central and posterior scalp regions. The P300 and N200 amplitude over the middle scalp location were stronger than the ones over left and right scalp locations. The influence of image content is not significant. The image quality could be assessed by P300 and N200 amplitude over the nine scalp areas, and the anterior and middle scalp areas have higher PLCC, SROCC, and KROCC values than other scalp areas. The influence of P300 amplitude on the estimated scores is smaller than that of N200 for most scalp areas. The result had a good correlation with subjective rating scores, which proved the feasibility of utilizing ERPs to assess image quality.

Are you mad at me? Social anxiety and early visual processing of anger and gaze among Asian American biculturals

Eyes are not universally attended to across different populations. Directly looking at the eyes of other people is a socially constrained behavior in many non-Western countries. Furthermore, perceiving emotions and faces are culturally regulated processes (Elfenbein and Ambady, in Psychol Bull 128(2):203–235, 2002; Caldara, in Curr Direct Psychol Sci 26(3):249–255, 2017). This study aims to bridge the gap between the cross-cultural and social cognition literature on gaze and threatening eye perception by understanding the relations between the early visual event-related potentials (ERPs) and social anxiety among Asian American biculturals. EEG was recorded from Asian American undergraduates while they watched isolated eye stimuli under four conditions: Angry Expression with an Averted Gaze, Angry Expression with a Direct Gaze, Neutral Expression with an Averted Gaze, and Neutral Expression with a Direct Gaze. The P1 ERP was sensitive to the combined effect of eye gaze and expression such that the largest amplitudes were recorded during the Angry-Averted eye condition. In contrast, no differences among the four conditions were found for the N170. Furthermore, we found an indirect effect between interdependent self-construal and social anxiety mediated by the P1. Interdependent self-construal was associated with smaller P1 s, which were related to greater social anxiety. The indirect effect supports the Asian American double bind (Lau et al., in Cult Divers Ethnic Minor Psychol 15(1), 77–85, 2009) and identifies a neural mechanism of lessened attention to eyes that may mediate increased social unease. These results emphasize the important role of culture in emotion perception via the eyes.

Event-Related Potentials in Relation to Risk-Taking: A Systematic Review.

Event-related potentials (ERPs) have been used to investigate neural mechanisms underlying risk-related decisions over the last 16 years. We aimed to systematically evaluate associations between risk-taking and ERP components elicited during decisions and following feedback. A total of 79 articles identified from PsychINFO and PubMed databases met the inclusion criteria. Selected articles assessed early ERP components (feedback-related negativity/FRN, error-related negativity/ERN, and medial frontal negativity/MFN) and the mid-latency P3 component, all using gambling paradigms that involved selecting between choices of varying risk (e.g., Iowa Gambling Task, Balloon Analogue Risk Task, and two-choice gambling tasks). The P3 component was consistently enhanced to the selection of risky options and when positive feedback (as compared to negative feedback) was provided. Also consistently, the early negative components were found to be larger following feedback indicating monetary losses as compared to gains. In the majority of studies reviewed here, risk was conceptualized in the context of simple economical decisions in gambling tasks. As such, this narrow concept of risk might not capture the diversity of risky decisions made in other areas of everyday experience, for example, social, health, and recreational risk-related decisions. It therefore remains to be seen whether the risk-sensitivity of the ERP components reviewed here generalizes to other domains of life.

Exploratory Study of rTMS Neuromodulation Effects on Electrocortical Functional Measures of Performance in an Oddball Test and Behavioral Symptoms in Autism.

There is no accepted pathology to autism spectrum disorders (ASD) but research suggests the presence of an altered excitatory/inhibitory (E/I) bias in the cerebral cortex. Repetitive transcranial magnetic stimulation (rTMS) offers a non-invasive means of modulating the E/I cortical bias with little in terms of side effects. In this study, 124 high functioning ASD children (IQ > 80, <18 years of age) were recruited and assigned using randomization to either a waitlist group or one of three different number of weekly rTMS sessions (i.e., 6, 12, and 18). TMS consisted of trains of 1.0 Hz frequency pulses applied over the dorsolateral prefrontal cortex (DLPFC). The experimental task was a visual oddball with illusory Kanizsa figures. Behavioral response variables included reaction time and error rate along with such neurophysiological indices such as stimulus and response-locked event-related potentials (ERP). One hundred and twelve patients completed the assigned number of TMS sessions. Results showed significant changes from baseline to posttest period in the following measures: motor responses accuracy [lower percentage of committed errors, slower latency of commission errors and restored normative post-error reaction time slowing in both early and later-stage ERP indices, enhanced magnitude of error-related negativity (ERN), improved error monitoring and post-error correction functions]. In addition, screening surveys showed significant reductions in aberrant behavior ratings and in both repetitive and stereotypic behaviors. These differences increased with the total number of treatment sessions. Our results suggest that rTMS, particularly after 18 sessions, facilitates cognitive control, attention and target stimuli recognition by improving discrimination between task-relevant and task-irrelevant illusory figures in an oddball test. The noted improvement in executive functions of behavioral performance monitoring further suggests that TMS has the potential to target core features of ASD.

Effects of Repeated Concussions and Sex on Early Processing of Emotional Facial Expressions as Revealed by Electrophysiology.

Concussions affect the processing of emotional stimuli. This study aimed to investigate how sex interacts with concussion effects on early event-related brain potentials (ERP) measures (P1, N1) of emotional facial expressions (EFE) processing in asymptomatic, multi-concussion athletes during an EFE identification task. Forty control athletes (20 females and 20 males) and 43 multi-concussed athletes (22 females and 21 males), recruited more than 3 months after their last concussion, were tested. Participants completed the Beck Depression Inventory II, the Beck Anxiety Inventory, the Post-Concussion Symptom Scale, and an Emotional Facial Expression Identification Task. Pictures of male and female faces expressing neutral, angry, and happy emotions were randomly presented and the emotion depicted had to be identified as fast as possible during EEG acquisition. Relative to controls, concussed athletes of both sex exhibited a significant suppression of P1 amplitude recorded from the dominant right hemisphere while performing the emotional face expression identification task. The present study also highlighted a sex-specific suppression of the N1 component amplitude after concussion which affected male athletes. These findings suggest that repeated concussions alter the typical pattern of right-hemisphere response dominance to EFE in early stages of EFE processing and that the neurophysiological mechanisms underlying the processing of emotional stimuli are distinctively affected across sex. (JINS, 2018, 24, 673-683).

The influence of behavioral relevance on the processing of global scene properties: An ERP study

Recent work studying the temporal dynamics of visual scene processing (Harel et al., 2016) has found that global scene properties (GSPs) modulate the amplitude of early Event-Related Potentials (ERPs). It is still not clear, however, to what extent the processing of these GSPs is influenced by their behavioral relevance, determined by the goals of the observer. To address this question, we investigated how behavioral relevance, operationalized by the task context impacts the electrophysiological responses to GSPs. In a set of two experiments we recorded ERPs while participants viewed images of real-world scenes, varying along two GSPs, naturalness (manmade/natural) and spatial expanse (open/closed). In Experiment 1, very little attention to scene content was required as participants viewed the scenes while performing an orthogonal fixation-cross task. In Experiment 2 participants saw the same scenes but now had to actively categorize them, based either on their naturalness or spatial expense. We found that task context had very little impact on the early ERP responses to the naturalness and spatial expanse of the scenes: P1, N1, and P2 could distinguish between open and closed scenes and between manmade and natural scenes across both experiments. Further, the specific effects of naturalness and spatial expanse on the ERP components were largely unaffected by their relevance for the task. A task effect was found at the N1 and P2 level, but this effect was manifest across all scene dimensions, indicating a general effect rather than an interaction between task context and GSPs. Together, these findings suggest that the extraction of global scene information reflected in the early ERP components is rapid and very little influenced by top-down observer-based goals.

F109. An event-related brain potential study of the arithmetic skills in college students

Introduction The arithmetic is fundamental in everyday life and represent an elemental part of learning of the individuals being a tool that allows an optimal performance in the resolution of problematic situations. One of the main research objectives of human behavior is understanding of cognitive processes such as arithmetic processing through neurophysiological techniques as the Event Related Potentials (ERPs). ERPs are a series of positive or negative oscillations, result of averaging segments where visual or auditory stimuli were presented to the participant during the electroencephalogram. Arithmetic processes have been associated to the Late Positive Component (LPC) located in central-parietal regions. Methods The sample consisted of 26 participants, 17 women and 9 men, with an average age of 21.3 years (SD ± 4.4 years). The EEG was performed with the software Curry XS Neuroscan System®, using 62 Au electrodes. The original file was converted, from data format to cnt format. The obtained signal was segmented in times with an analysis window of −400 to 1600 ms, rejection of muscular and ocular artifact was made, with Independent Component Analysis. Both the verification and the production paradigms were presented on a monitor with a resolution of 1280 × 960 pixels during the EEG. The verification paradigm had a total of 80 arithmetic operations of integers with a possible response, the participant had to answer if the response showed was either correct or incorrect, to record the responses a board with two buttons was used, one button for the correct answer and one for the incorrect answer. The production paradigm had a total of 80 arithmetic operations of whole numbers, the participant had to answer verbally during a neutral stimulus. With sampling frequency of 1000 Hz. Each arithmetic operation lasted 4000 ms followed by a neutral stimulus (a point in the center of the screen) with a duration of 500 ms where the participant gave the answer. The analyses with the EEGLAB tool of the MATLAB software. The PREs of each participant were analyzed and then the average of each stimulus was made Results The right answers in the complex operations were significantly lower than the those in the simple operations x2 (1, N = 80) = 42.89, p Conclusion There were no differences in the right answers of the participants between experimental paradigms. The type of operation and its difficulty did not affect the early ERPs however amplitude of the LPC appears to be sensitive to arithmetic production tasks.

Intuitive Assessment of Mortality Based on Facial Characteristics: Behavioral, Electrocortical, and Machine Learning Analyses

Studies of various characteristics of the human face indicate that it contains a wealth of information about health status. Most studies involve objective measurement of facial features as correlated with historical health information. But some individuals also claim to be adept at intuitively gauging mortality based solely upon a quick glance at a person's photograph. To test this claim, we invited 12 such individuals to see if they could tell if a person was alive or dead based solely on a brief examination of his or her photograph. All photos used in the experiment were transformed into a uniform gray scale and counterbalanced across eight categories as follows: gender, age, gaze direction, glasses, head position, smile, hair color, and image resolution. Participants examined 404 photographs displayed on a computer monitor, one photo at a time, each shown for a maximum of 8seconds. Half of the individuals in the photos were deceased, and half were alive at the time the experiment was conducted. Participants were asked to indicate if they thought the person in a photo was living or deceased by pressing an appropriate button. Overall, mean accuracy on this task was 53.6%, where 50% was expected by chance (P = .005, two tail). Statistically significant accuracy was independently obtained in 5 of the 12 participants. We also collected 32-channel electrocortical recordings and observed a robust difference between images of deceased individuals correctly vs. incorrectly classified in the early event related potential at 100ms post-stimulus onset. We then applied machine learning techniques to classify the photographs based on 11 image characteristics; both random forest and logistic regression machine learning approaches were used, and both classifiers failed to achieve accuracy above chance level. Our results suggest that some individuals can intuitively assess mortality based on some as-yet unknown features of the face.

The spatio-temporal dynamics of deviance and target detection in the passive and active auditory oddball paradigm: a sLORETA study

BackgroundNumerous studies have investigated the neural underpinnings of passive and active deviance and target detection in the well-known auditory oddball paradigm by means of event-related potentials (ERPs) or functional magnetic resonance imaging (fMRI). The present auditory oddball study investigates the spatio-temporal dynamics of passive versus active deviance and target detection by analyzing amplitude modulations of early and late ERPs while at the same time exploring the neural sources underling this modulation with standardized low-resolution brain electromagnetic tomography (sLORETA).MethodsA 64-channel EEG was recorded from twelve healthy right-handed participants while listening to ‘standards’ and ‘deviants’ (500 vs. 1000 Hz pure tones) during a passive (block 1) and an active (block 2) listening condition. During passive listening, participants had to simply listen to the tones. During active listening they had to attend and press a key in response to the deviant tones.ResultsPassive and active listening elicited an N1 component, a mismatch negativity (MMN) as difference potential (whose amplitudes were temporally overlapping with the N1) and a P3 component. N1/MMN and P3 amplitudes were significantly more pronounced for deviants as compared to standards during both listening conditions. Active listening augmented P3 modulation to deviants significantly compared to passive listening, whereas deviance detection as indexed by N1/MMN modulation was unaffected by the task. During passive listening, sLORETA contrasts (deviants > standards) revealed significant activations in the right superior temporal gyrus (STG) and the lingual gyri bilaterally (N1/MMN) as well as in the left and right insulae (P3). During active listening, significant activations were found for the N1/MMN in the right inferior parietal lobule (IPL) and for the P3 in multiple cortical regions (e.g., precuneus).DiscussionThe results provide evidence for the hypothesis that passive as well as active deviance and target detection elicit cortical activations in spatially distributed brain regions and neural networks including the ventral attention network (VAN), dorsal attention network (DAN) and salience network (SN). Based on the temporal activation of the neural sources underlying ERP modulations, a neurophysiological model of passive and active deviance and target detection is proposed which can be tested in future studies.

Discontinuity of early and late event-related brain potentials for selective attention in dichotic listening.

If a representation of an auditory attention channel was present in the auditory cortices but not in the subcortical structures, it would be predicted that the early event-related brain potential (ERP) would disagree with the late ERP in selective attention effects. To examine this idea, the present study recorded the auditory brain stem response (ABR) as an early ERP and also the negative difference, the processing negativity and the irrelevant positive difference waves as late ERPs during dichotic listening. Each participant experienced two dichotic conditions: (i) 500-Hz standard tones to the left ear and 1000-Hz ones to the right ear (L500/R1000), (ii) 1000-Hz standard tones to the left ear and 500-Hz ones to the right ear (L1000/R500). In a control task, participants performed visual detection and ignored auditory stimuli. Although the negative difference and processing negativity were found to be identical between the two dichotic conditions, the ABR demonstrated a significant difference between relevant and irrelevant tasks only for the L500/R1000 condition. A response preference to lower-frequency tones was found for behavioural measures and late ERPs but not for the ABR. These results suggest difficulty in representing attention channels in the auditory brain stem. In addition, a weak effect of dichotic sound combination in behaviours corresponded only with earlier ERPs.

Event Related Potential Study of Language Interaction in Bilingual Aphasia Patients.

Half of the global population can be considered bilingual. Nevertheless when faced with patients with aphasia, clinicians and therapists usually ignore the patient’s second language (L2) albeit its interference in first language (L1) processing has been shown. The excellent temporal resolution by which each individual linguistic component can be gaged during word-processing, promoted the event-related potential (ERP) technique for studying language processing in healthy bilinguals and monolingual aphasia patients. However, this technique has not yet been applied in the context of bilingual aphasia. In the current study, we report on L2 interference in L1 processing using the ERP technique in bilingual aphasia. We tested four bilingual- and one trilingual patients with aphasia, as well as several young and older (age-matched with patients) healthy subjects as controls. We recorded ERPs when subjects were engaged in a semantic association judgment task on 122 related and 122 unrelated Dutch word-pairs (prime and target words). In 61 related and 61 unrelated word-pairs, an inter-lingual homograph was used as prime. In these word-pairs, when the target was unrelated to the prime in Dutch (L1), it was associated to the English (L2) meaning of the homograph. Results showed a significant effect of homograph use as a prime on early and/or late ERPs in response to word-pairs related in Dutch or English. Each patient presented a unique pattern of L2 interference in L1 processing as reflected by his/her ERP image. These interferences depended on the patient’s pre- and post-morbid L2 proficiency. When the proficiency was high, the L2 interference in L1 processing was higher. Furthermore, the mechanism of interference in patients that were pre-morbidly highly proficient in L2 additionally depended on the frequency of pre-morbid L2 exposure. In summary, we showed that the mechanism behind L2 interference in L1 processing in bilingual patients with aphasia depends on a complex interaction between pre- and post-morbid L2 proficiency, pre- and post-morbid L2 exposure, impairment and the presented stimulus (inter-lingual homographs). Our ERP study complements the usually adopted behavioral approach by providing new insights into language interactions on the level of individual linguistic components in bilingual patients with aphasia.

ERP Source Analysis Guided by fMRI During Familiar Face Processing.

Event related potentials (ERPs) provide precise temporal information about cognitive processing, but with poor spatial resolution, while functional magnetic resonance imaging (fMRI) reliably identifies brain areas involved, but with poor temporal resolution. Here we use fMRI to guide source localization of the ERPs at different times for studying the temporal dynamics of the neural system for recognizing familiar faces. fMRI activation areas were defined in a previous experiment applying the same paradigm used for ERPs. The Bayesian model averaging (BMA) method was used to estimate the generators of the ERPs to unfamiliar, visually familiar, and personally-familiar faces constraining the model by fMRI activation results. For this, higher prior probabilities in the solution space were assigned to the fMRI-defined regions, which included face-selective areas and other areas related to "person knowledge" retrieval. Source analysis was carried out in three-time windows: early (150-210ms), middle (300-380ms) and late (460-580ms). The early and middle responses were generated in fMRI-defined areas for all face categories, while these areas do not contribute to the late response. Different areas contributed to the generation of the early and middle ERPs elicited by unfamiliar faces: fusiform (Fus), inferior occipital, superior temporal sulcus and the posterior cingulate (PC) cortices. For familiar faces, the contributing areas were Fus, PC and anterior temporal areas for visually familiar faces, with the addition of the medial orbitofrontal areas and other frontal structures for personally-significant faces. For both unfamiliar and familiar faces, more extended and reliable involvement of contributing areas were obtained for the middle compare with early time window. Our fMRI guide ERP source analysis suggested the recruitment of person-knowledge processing areas as early as 150-210ms after stimulus onset during recognition of personally-familiar faces. We concluded that fMRI-constrained BMA source analysis provide information regarding the temporal-dynamics in the neural system for cognitive processsing.

Early visual ERPs show stable body-sensitive patterns over a 4-week test period.

Event-related potential (ERP) studies feature among the most cited papers in the field of body representation, with recent research highlighting the potential of ERPs as neuropsychiatric biomarkers. Despite this, investigation into how reliable early visual ERPs and body-sensitive effects are over time has been overlooked. This study therefore aimed to assess the stability of early body-sensitive effects and visual P1, N1 and VPP responses. Participants were asked to identify pictures of their own bodies, other bodies and houses during an EEG test session that was completed at the same time, once a week, for four consecutive weeks. Results showed that amplitude and latency of early visual components and their associated body-sensitive effects were stable over the 4-week period. Furthermore, correlational analyses revealed that VPP component amplitude might be more reliable than VPP latency and specific electrode sites might be more robust indicators of body-sensitive cortical activity than others. These findings suggest that visual P1, N1 and VPP responses, alongside body-sensitive N1/VPP effects, are robust indications of neuronal activity. We conclude that these components are eligible to be considered as electrophysiological biomarkers relevant to body representation.

EEG and ERP biomarkers of Alzheimer's disease: a critical review.

Here we critically review studies that used electroencephalography (EEG) or event-related potential (ERP) indices as a biomarker of Alzheimer's disease. In the first part we overview studies that relied on visual inspection of EEG traces and spectral characteristics of EEG. Second, we survey analysis methods motivated by dynamical systems theory (DST) as well as more recent network connectivity approaches. In the third part we review studies of sleep. Next, we compare the utility of early and late ERP components in dementia research. In the section on mismatch negativity (MMN) studies we summarize their results and limitations and outline the emerging field of computational neurology. In the following we overview the use of EEG in the differential diagnosis of the most common neurocognitive disorders. Finally, we provide a summary of the state of the field and conclude that several promising EEG/ERP indices of synaptic neurotransmission are worth considering as potential biomarkers. Furthermore, we highlight some practical issues and discuss future challenges as well.