EEG Event-related Potentials Research Articles

Gut inference: A computational modelling approach

Neurocomputational theories have hypothesized that Bayesian inference underlies interoception, which has become a topic of recent experimental work in heartbeat perception. To extend this approach beyond cardiac interoception, we describe the application of a Bayesian computational model to a recently developed gastrointestinal interoception task completed by 40 healthy individuals undergoing simultaneous electroencephalogram (EEG) and peripheral physiological recording. We first present results that support the validity of this modelling approach. Second, we provide a test of, and confirmatory evidence supporting, the neural process theory associated with a particular Bayesian framework (active inference) that predicts specific relationships between computational parameters and event-related potentials in EEG. We also offer some exploratory evidence suggesting that computational parameters may influence the regulation of peripheral physiological states. We conclude that this computational approach offers promise as a tool for studying individual differences in gastrointestinal interoception.

The N250 event-related potential as an index of face familiarity: a replication study

The neural correlates of face individuation—the acquisition of memory representations for novel faces—have been studied only in coarse detail and disregarding individual differences between learners. In their seminal study, Tanaka et al. (Tanaka et al. 2006 J. Cogn. Neurosci. 18, 1488–1497. (doi:10.1162/jocn.2006.18.9.1488)) required the identification of a particular novel face across 70 trials and found that the N250 component in the EEG event-related potentials became more negative from the first to the second half of the experiment, where it reached a similar amplitude as a well-known face. We were unable to directly replicate this finding in our study when we used the original split of trials. However, when we applied a different split of trials we observed very similar changes in N250 amplitude. We conclude that the N250 component is indeed sensitive to the build-up of a robust representation of a face in memory; the time course of this process appears to vary as a function of variables that may be determined in future research.

Comparing physiological responses during cognitive tests in virtual environments vs. in identical real-world environments

Immersive virtual environments (VEs) are increasingly used to evaluate human responses to design variables. VEs provide a tremendous capacity to isolate and readily adjust specific features of an architectural or product design. They also allow researchers to safely and effectively measure performance factors and physiological responses. However, the success of this form of design-testing depends on the generalizability of response measurements between VEs and real-world contexts. At the current time, there is very limited research evaluating the consistency of human response data across identical real and virtual environments. Rendering tools were used to precisely replicate a real-world classroom in virtual space. Participants were recruited and asked to complete a series of cognitive tests in the real classroom and in the virtual classroom. Physiological data were collected during these tests, including electroencephalography (EEG), electrocardiography (ECG), electrooculography (EOG), galvanic skin response (GSR), and head acceleration. Participants’ accuracy on the cognitive tests did not significantly differ between the real classroom and the identical VE. However, the participants answered the tests more rapidly in the VE. No significant differences were found in eye blink rate and heart rate between the real and VR settings. Head acceleration and GSR variance were lower in the VE setting. Overall, EEG frequency band-power was not significantly altered between the real-world classroom and the VE. Analysis of EEG event-related potentials likewise indicated strong similarity between the real-world classroom and the VE, with a single exception related to executive functioning in a color-mismatch task.

NEUROMARKERS OF ANXIETY IN A PATIENT WHO HAD EXPERIENCED A TRANSIENT ISCHEMIC ATTACK (TIA) OF THE LEFT BRAIN HEMISPHERE AS A RESULT OF A CRITICAL STENOSIS OF THE INTERNAL CAROTID ARTERY (ICA) OPERATED ON BY ENDARTERECTOMY (CEA)

The search for neuromarkers is a very promising way to improve psychiatric and psychological care. They are now considered to be an innovative diagnostic tool in psychiatry and neuropsychology, but more broadly in all human health sciences. The aim of our study was to find the neuromarker of anxiety in a patient who had experienced a Transient IschemicAttack (TIA) of the left brain hemisphere as a result of a critical stenosis of the Internal Carotid Artery (ICA) operated on byendarterectomy (CEA). We will present the case of a 54-year-old man,an architect, who experienced a Transient Ischemic Attack (TIA) of the left brain hemispherecaused by a critical stenosis of theInternal Carotid Artery (ICA) and was treated successfully with surgical endarterectomy (CEA). One year after the surgery itself, the patient developed severe postoperative anxiety, headaches, difficulty in sleepingas well as the inability to continue working in his profession. Strong anxiety was notedon the adapted 100-millimeter Visual Analogue Anxiety Scale (VAAS). The patient was assessed using the Human Brain Index (HBI) methodology (Kropotov 2009; 2016; 2017; Pąchalska, Kaczmarek&Kropotov 2014) which consisted of recording 19-channel EEG in resting state conditions, during the cued GO/NOGO task and comparing the parameters of EEG spectra and Event-Related Potentials (ERPs) with the normative and patient databases of the Human Brain Index(HBI). No signs of cognitive dysfunction was found, however an excessive Rolandic beta was observed. In line with the working hypothesis as to the presence of an anxiety neuromarker, the patient’s studies confirmed an increased P1 time wave in the left hemisphere of the brain in ERP in response to visual stimuli, i.e. an anxiety neuromarker. Following the detection of this neuromarkera specific anodic Transcranial Direct Current Stimulations (tDCS) protocol was proposed (see: Kropotov 2016; Pąchalska, Kaczmarek & Kropotov 2020). Ten tDCS sessions were performed and the postoperativeanxiety was found to be resolved. The patient returned to work. The use of Human Brain Index (HBI) methodologyenabling the isolation of the Event Related Potentials (ERPs) patterns revealed the presence of a distinct anxietyneuromarker. Neurotherapy with the use of tDCS allowed the reduction of anxiety symptoms and the patient’s return to work. The above case study indicates the necessity to use new neurotechnologies in the diagnosis of mental diseases, with particular emphasis on postoperative anxiety.

EEG Resting-State and Event-Related Potentials as Markers of Learning Success in Older Adults Following Second Language Training: A Pilot Study.

Objectives:In this pilot study, we evaluated the use of electrophysiological measures at rest as paradigm-independent predictors of second language (L2) development for the first time in older adult learners. We then assessed EEG correlates of the learning outcome in a language-switching paradigm after the training, which to date has only been done in younger adults and at intermediate to advanced L2 proficiency.Methods:Ten (Swiss) German-speaking adults between 65–74 years of age participated in an intensive 3-week English training for beginners. A resting-state EEG was recorded before the training to predict the ensuing L2 development (Experiment 1). A language-switching ERP experiment was conducted after the training to assess the learning outcome (Experiment 2).Results:All participants improved their L2 skills but differed noticeably in their individual development. Experiment 1 showed that beta1 oscillations at rest (13–14.5 Hz) predicted these individual differences. We interpret resting-state beta1 oscillations as correlates of attentional capacities and semantic working memory that facilitate the extraction and processing of novel forms and meanings from the L2 input.In Experiment 2, we found that language switching from the L2 into the native language (L1) elicited an N400 component, which was reduced in the more advanced learners. Thus, for learners beginning the acquisition of an L2 in third age, language switching appears to become less effortful with increasing proficiency, suggesting that the lexicons of the L1 and L2 become more closely linked.Conclusions:In sum, our findings extend the available evidence of neurological processes in L2 learning from younger to older adults, suggesting that electrophysiological mechanisms are similar across the lifespan.

EEG event related potentials in sustained, focused and divided attention tasks: Potential biomarkers for cognitive impairment in HIV patients

ObjectivesThe objective of this study was to assess the usability of event-related-potentials (ERPs) during sustained, focused, and divided attention tasks as biomarkers for cognitive decline in HIV patients. MethodsEEG was acquired using a mobile/wireless 9-channel system in 39 persons with HIV, with well-controlled immune function and 63 healthy control participants (HCs) during three ERP tasks: sustained attention, focused attention, and divided attention. ResultsThe HIV-group evidenced smaller late positive potential (LPP) and larger P200 amplitudes across the tasks compared to the HC group. P200 amplitude was correlated (r = 0.56) with the estimated duration of infection. Both groups showed higher P200 and LPP amplitudes in response to infrequent stimuli; this effect was not significantly different between groups. In the sustained attention task, the HIV-group showed significantly slower reaction time than controls while maintaining the same level of accuracy. In the divided attention task, the HIV-group showed a trend towards faster/less accurate responses. ConclusionsHIV seropositive participants receiving anti-retroviral treatment (ART) demonstrated significantly larger P200 amplitude during three different attention tasks. This may reflect attentional deficits characterized by over-attending to non-target/distracting stimuli. SignificanceThese findings demonstrate the potential benefits of EEG-ERP metrics derived from attention tasks as neurocognitive biomarkers for HIV. This approach may reveal underlying causes of attentional deficits in HIV patients.

Boosts in brain signal variability track liberal shifts in decision bias.

Adopting particular decision biases allows organisms to tailor their choices to environmental demands. For example, a liberal response strategy pays off when target detection is crucial, whereas a conservative strategy is optimal for avoiding false alarms. Using conventional time-frequency analysis of human electroencephalographic (EEG) activity, we previously showed that bias setting entails adjustment of evidence accumulation in sensory regions (Kloosterman et al., 2019), but the presumed prefrontal signature of a conservative-to-liberal bias shift has remained elusive. Here, we show that a liberal bias shift is reflected in a more unconstrained neural regime (boosted entropy) in frontal regions that is suited to the detection of unpredictable events. Overall EEG variation, spectral power and event-related potentials could not explain this relationship, highlighting that moment-to-moment neural variability uniquely tracks bias shifts. Neural variability modulation through prefrontal cortex appears instrumental for permitting an organism to adapt its biases to environmental demands.

Event-related potential and EEG oscillatory predictors of verbal memory in mild cognitive impairment.

Reliable biomarkers of memory decline are critical for the early detection of Alzheimer’s disease. Previous work has found three EEG measures, namely the event-related brain potential P600, suppression of oscillatory activity in the alpha frequency range (∼10 Hz) and cross-frequency coupling between low theta/high delta and alpha/beta activity, each of which correlates strongly with verbal learning and memory abilities in healthy elderly and patients with mild cognitive impairment or prodromal Alzheimer’s disease. In the present study, we address the question of whether event-related or oscillatory measures, or a combination thereof, best predict the decline of verbal memory in mild cognitive impairment and Alzheimer’s disease. Single-trial correlation analyses show that despite a similarity in their time courses and sensitivities to word repetition, the P600 and the alpha suppression components are minimally correlated with each other on a trial-by-trial basis (generally |rs| < 0.10). This suggests that they are unlikely to stem from the same neural mechanism. Furthermore, event-related brain potentials constructed from bandpass filtered (delta, theta, alpha, beta or gamma bands) single-trial data indicate that only delta band activity (1–4 Hz) is strongly correlated (r = 0.94, P < 0.001) with the canonical P600 repetition effect; event-related potentials in higher frequency bands are not. Importantly, stepwise multiple regression analyses reveal that the three event-related brain potential/oscillatory measures are complementary in predicting California Verbal Learning Test scores (overall R2’s in 0.45–0.63 range). The present study highlights the importance of combining EEG event-related potential and oscillatory measures to better characterize the multiple mechanisms of memory failure in individuals with mild cognitive impairment or prodromal Alzheimer’s disease.

Detection rates of chemosensory evoked Potenzials with healthy andanosmic subjects

The detection rate of olfactory chemosensory event-related EEG Potentials (oCSERP) and trigeminal chemosensory event-related EEG Potentials (tCSERP) is also dependent on the stimulants and the evaluator of the averaged EEG curves. In 45 subjects with age-appropriate normal olfactory capacity (NP) and 20 anosmics (AN), oCSERP (stimulation by hydrogen sulphide, H2S 6 ppm and phenylethyl alcohol, PEA 30 % v/v,) and tCSERP (irritation with CO2 20-60 % v/v, intensity standardized) were derived by default. Two investigators categorized the averaged EEG curves in: CSERP recognizable, no CSERP recognizable and artefact. Investigator 1 knew whether the subject was a NP or an AN, and which stimulants was used, whereas investigator 2 lacked this information. AN needed higher trigeminal stimulus concentrations but showed same intensity ratings compared to NP. The attention (tracking game) did not deteriorate in the course of test. The detection rate of H2S-CSERP was higher than that of PEA-CSERP. The match of H2S-CSERP detection rates between the two investigators was higher than that of PEA-CSERP and CO2-CSERP. For the standard derivation of oCSERP, stimulation with H2S is usually sufficient. Stimulation with PEA and CO2 as well as a blinded investigator is not necessary.

M53. EMOTIONAL SELF-VOICE PROCESSING AND ITS RELATIONSHIP WITH HALLUCINATORY PRONENESS

BackgroundSensory brain areas typically reduce their activity when we speak, allowing us to differentiate our own from someone else’s speech. Similarly, the amplitude of the N100 component of the EEG event-related potential in response to own speech is smaller than for passive listening to own or someone else’s speech. This amplitude suppression effect seems to be altered in voice hearers, which in turn could result in source misattribution (e.g., self-produced voice attributed to an external source). Emotion in speech can have a comparable effect, altering not only self-voice processing but also differentiation of the quality of auditory hallucinations in clinical and non-clinical voice hearers. For example, unlike in non-clinical voice hearers, auditory hallucinations in clinical voice hearers are usually derogatory in content and negatively affect daily functioning. Recent research strongly suggests that clinical and non-clinical voice hearers lie on a continuum ranging from low to high hallucinatory proneness. Based on this notion, the present study used EEG to investigate the effects of manipulations of self-voice quality in self-generated and passively listened-to self-voice as a function of hallucinatory proneness (HP) in healthy young adults. This is the first EEG study that examined the interplay of sensory suppression, emotion, and HP in a non-clinical population.MethodsParticipants varying in HP (according to the Launay Slade Hallucination Scale) participated in a standardized button-press task to elicit their own voice (compared to passively listening to it) in which the self-voice changed stepwise from fully neutral to fully emotional. The experimental task comprised three conditions: motor-to-auditory (MA), where the button-press generated the voice, auditory only (AO), where the voice was presented without the button press, and motor only (MO-a control condition to remove the motor related artifacts from the MA condition), where the button press did not generate the voice. Neutral and angry self-voice (single syllable ‘ah’ and ‘oh’ vocalizations of 500 ms duration) were recorded for each participant before the EEG acquisition. These voices were morphed to generate a neutral to angry continuum consisting of five stimuli ranging from fully neutral to fully angry: 100% neutral, 60-40% neutral-angry, 50-50% neutral-angry and 40–60% neutral-angry and 100% angry.ResultsPreliminary results with 17 participants show a significant effect of emotional self-voice quality on N1 suppression effect, with a larger suppression effect for the 100% angry as compared to 100% neutral self-voice. On the other hand, 60-40% neutral-angry, 50-50% neutral-angry and 40–60% neutral-angry self-voice show an enhancement effect. Furthermore, the results show a significant interaction of HP and voice quality on N1 suppression effect such that high HP showed no N1 suppression effect for the 100% neutral self-voice and an enhanced N1 effect when emotional quality of the self-voice increased.DiscussionThese data suggest that participants perceive the manipulations in the self-voice quality such that they recognize their own fully neutral and angry voice depicted by N100 suppression effect. Similarly, an N100 enhancement effect for 50-50% neutral-angry voice suggest that it is perceived as the most uncertain or peculiar of all the stimuli. Further, low and high HP show difference in N100 suppression effect for different voices, suggesting that HP may alter self-voice processing and these alterations are enhanced for emotional self-voice. This further supports the fact that abnormal perceptual experiences in voice hearers are higher when auditory hallucinations are emotional in nature.

Dopaminergic and noradrenergic manipulation of anticipatory reward and probability event-related potentials

Predicting what will happen in the future in terms of potential reward is essential in daily life. The aim of the current study was to investigate the neurotransmitter systems involved in the anticipation of reward value and probability. We hypothesized that dopaminergic and noradrenergic antagonism would affect anticipation of reward value and probability, respectively. Twenty-three healthy participants were included in a haloperidol (2 mg) × clonidine (0.150 mg) × placebo cross-over design and subjected to a Go/NoGo experimental task during which cues signaled the probability of subsequent target appearance. Reward value (amount of money that could be won for correct and fast responding to the target) as well as probability of target appearance was orthogonally manipulated across four task blocks. Cue-elicited EEG event-related potentials were recorded to assess anticipation of value and probability, respectively. The processing of reward value was affected by dopaminergic antagonism (haloperidol), as evidenced by reduction of the reward-related positivity and P300 to reward cues. This reduction was specifically significant for subjects with high baseline dopamine levels for the P300 and most pronounced for these subjects for the reward-related positivity. In contrast, the processing of reward probability was affected by noradrenergic antagonism (clonidine). In addition, both drugs reduced overall performance (omission rate, response speed variability). We conclude that at least anticipation of reward value and probability, respectively, is specifically affected by dopaminergic versus noradrenergic antagonism.

Differential effects of traxoprodil and S-ketamine on quantitative EEG and auditory event-related potentials as translational biomarkers in preclinical trials in rats and mice

Quantitative Electroencephalography (qEEG) and event-related potential (ERP) assessment have emerged as powerful tools to unravel translational biomarkers in preclinical and clinical psychiatric drug discovery trials. The aim of the present study was to compare the GluN2B negative allosteric modulator (NAM) traxoprodil (CP-101,606) with the unselective NMDA receptor channel blocker S-ketamine to give insight into central target engagement and differentiation on multiple EEG readouts.For qEEG recordings telemetric transmitters were implanted in male Wistar rats. Recorded EEG data were analyzed using fast Fourier transformation to determine power spectra and vigilance states. Additionally, body temperature and locomotor activity were assessed via telemetry. For recordings of auditory event-related potentials (AERP) male C57Bl/6J mice were chronically implanted with deep electrodes using a tethered system.Power spectral analysis revealed a significant increase in gamma power following ketamine treatment, whereas traxoprodil (6&18 mg/kg) induced an overall decrease primarily within alpha and beta bands. Additionally, ketamine disrupted sleep and enhanced time spent in wake vigilance states, whereas traxoprodil did not alter sleep-wake architecture. AERP and mismatch negativity (MMN) revealed that ketamine (10 mg/kg) selectively disrupts auditory deviance detection, whereas traxoprodil (6 mg/kg) did not alter MMN at clinically relevant doses. In contrast to ketamine treatment, traxoprodil did not produce hyperactivity and hypothermia.In conclusion, ketamine and traxoprodil showed very different effects on diverse EEG readouts differentiating selective GluN2B antagonism from non-selective pan-NMDA-R antagonists like ketamine. These readouts are thus perfectly suited to support drug discovery efforts on NMDA-R and understanding the different functions of NMDA-R subtypes.

Get Set or Get Distracted? Disentangling Content-Priming and Attention-Catching Effects of Background Lure Stimuli on Identifying Targets in Two Simultaneously Presented Series.

In order to study the changing relevance of stimulus features in time and space, we used a task with rapid serial presentation of two stimulus streams where two targets (“T1” and “T2”) had to be distinguished from background stimuli and where the difficult T2 distinction was impeded by background stimuli presented before T1 that resemble T2 (“lures”). Such lures might actually have dual characteristics: Their capturing attention might interfere with target identification, whereas their similarity to T2 might result in positive priming. To test this idea here, T2 was a blue digit among black letters, and lures resembled T2 either by alphanumeric category (black digits) or by salience (blue letters). Same-category lures were expected to prime T2 identification whereas salient lures would impede T2 identification. Results confirmed these predictions, yet the precise pattern of results did not fit our conceptual framework. To account for this pattern, we speculate that lures serve to confuse participants about the order of events, and the major factor distinguishing color lures and digit lures is their confusability with T2. Mechanisms of effects were additionally explored by measuring event-related EEG potentials. Consistent with the assumption that they attract more attention, color lures evoked larger N2pc than digit lures and affected the ensuing T1-evoked N2pc. T2-evoked N2pc was indistinguishably reduced by all kinds of preceding lures, though. Lure-evoked mesio-frontal negativity increased from first to third lures both with digit and color lures and, thereby, might have reflected expectancy for T1.

Multimodal exploration of non-motor neural functions in ALS patients using simultaneous EEG-fNIRS recording

Objective. Despite the high prevalence of non-motor impairments reported in patients with amyotrophic lateral sclerosis (ALS), little is known about the functional neural markers underlying such dysfunctions. In this study, a new dual-task multimodal framework relying on simultaneous electroencephalogram (EEG) and functional near-infrared spectroscopy (fNIRS) recordings was developed to characterize integrative non-motor neural functions in people with ALS. Approach. Simultaneous EEG-fNIRS data were recorded from six subjects with ALS and twelve healthy controls. Through a proposed visuo-mental paradigm, subjects performed a set of visuo-mental arithmetic operations. The data recorded were analyzed with respect to event-related changes both in the time and frequency domains for EEG and de/oxygen-hemoglobin level (HbR/HbO) changes for fNIRS. The correlation of EEG spectral features with fNIRS HbO/HbR features were then evaluated to assess the mechanisms of ALS on the electrical (EEG)-vascular (fNIRS) interrelationships. Main results. We observed overall smaller increases in EEG delta and theta power, decreases in beta power, reductions in HbO responses, and distortions both in early and later EEG event-related potentials in ALS subjects compared to healthy controls. While significant correlations between EEG features and HbO responses were observed in healthy controls, these patterns were absent in ALS patients. Distortions in both electrical and hemodynamic responses are speculated to be associated with cognitive deficits in ALS that center primarily on attentional and working memory processing. Significance. Our results highlight the important role of ALS non-motor dysfunctions in electrical and hemodynamic neural dynamics as well as their interrelationships. The insights obtained through this study can enhance our understanding of the underlying non-motor neural processes in ALS and enrich future diagnostic and prognostic techniques.

Convolutional neural networks for decoding of covert attention focus and saliency maps for EEG feature visualization

Objective. Convolutional neural networks (CNNs) have proven successful as function approximators and have therefore been used for classification problems including electroencephalography (EEG) signal decoding for brain–computer interfaces (BCI). Artificial neural networks, however, are considered black boxes, because they usually have thousands of parameters, making interpretation of their internal processes challenging. Here we systematically evaluate the use of CNNs for EEG signal decoding and investigate a method for visualizing the CNN model decision process. Approach. We developed a CNN model to decode the covert focus of attention from EEG event-related potentials during object selection. We compared the CNN and the commonly used linear discriminant analysis (LDA) classifier performance, applied to datasets with different dimensionality, and analyzed transfer learning capacity. Moreover, we validated the impact of single model components by systematically altering the model. Furthermore, we investigated the use of saliency maps as a tool for visualizing the spatial and temporal features driving the model output. Main results. The CNN model and the LDA classifier achieved comparable accuracy on the lower-dimensional dataset, but CNN exceeded LDA performance significantly on the higher-dimensional dataset (without hypothesis-driven preprocessing), achieving an average decoding accuracy of 90.7% (chance level = 8.3%). Parallel convolutions, tanh or ELU activation functions, and dropout regularization proved valuable for model performance, whereas the sequential convolutions, ReLU activation function, and batch normalization components reduced accuracy or yielded no significant difference. Saliency maps revealed meaningful features, displaying the typical spatial distribution and latency of the P300 component expected during this task. Significance. Following systematic evaluation, we provide recommendations for when and how to use CNN models in EEG decoding. Moreover, we propose a new approach for investigating the neural correlates of a cognitive task by training CNN models on raw high-dimensional EEG data and utilizing saliency maps for relevant feature extraction.

Brain state monitoring for the future prediction of migraine attacks.

Migraine attacks are unpredictable, precluding preemptive interventions and leading to lack of control over individuals' lives. Although there are neurophysiological changes 24-48 hours before migraine attacks, so far, they have not been used in patients' management. This study evaluates the applicability and the ability to identify pre-attack changes of daily "at home" electroencephalography obtained with a portable system for migraine patients. Patients with episodic migraine fulfilling ICHD-3 beta criteria used a mobile system composed of a wireless EEG device (BrainStation®, Neuroverse®, Inc., USA) and mobile application (BrainVitalsM®, Neuroverse®, Inc., USA) to self-record their neural activity daily at home while resting and while performing an attention task, over the course of 2 weeks. Standard EEG spectral analysis and event-related brain potentials (ERP) methods were used and recordings were grouped by time from migraine attacks (i.e. "Interictal day", "24 h Before Migraine", "Migraine day" and "Post Migraine"). Twenty-four patients (22 women) recorded an average of 13.3 ± 1.9 days and had 2 ± 0.9 attacks. Twenty-four hours before attack onset, there was a statistically significant modulation of relative power in the delta (decrease) and beta (increase) frequency bands, at rest, and a significant reduction of the amplitude and inter-trial coherence measures of an attention event-related brain potential (P300). This proof-of-concept study shows that brain state monitoring, utilising an easy-to-use wearable EEG system to track neural modulations at home, can identify physiological changes preceding a migraine attack enabling valuable pre-symptom prediction and subsequent early intervention.

Exploration of the Impact of Brief Noninvasive Vagal Nerve Stimulation on EEG and Event-Related Potentials

The primary objective of this study was to explore the impact of noninvasive Vagal Nerve Stimulation (nVNS) on brain electrophysiology, as assessed through spontaneous resting-state EEG and stimulus-driven event-related potentials (ERPs). A hand-held transcutaneous stimulator was placed on the neck over the main branch of the left vagus (active condition) or more laterally over neck muscles (sham condition), with two 120-sec long bursts of stimulation applied over a five-minute period. For each of eight neurotypical subjects, prior to stimulation, and then again beginning at 15, 120, and 240 min post-stimulation, ten minutes of background EEG data were collected, along with a series of ERPs-N100 auditory sensory-gating; the N1/P2 loudness dependent auditory evoked responses (LDAER); mismatch negativity; P300a; and P300b. Each subject participated in active and sham stimulation sessions. Brief nVNS had a significant (p < 0.05), and in some cases prolonged (>2 hours), impact on the spontaneous EEG (decreased theta and alpha, and increased beta and gamma), and on sensory gating, LDAER, and P300b evoked responses. Based on prior literature, these specific observations may reflect nVNS-induced modulation of particular neurotransmitter systems including those for GABA (gamma power and frequency); acetylcholine (sensory gating); serotonin (LDAER); and noradrenaline (P300b). Brief nVNS leads to changes in a sub-set of resting-state and event-related electrophysiologic indices of brain activity. These changes are believed to be mediated by vagal afferent projections to the nucleus of the solitary tract, which in turn regulates several neurotransmitter systems through known direct and indirect neuroanatomic pathways.

ELECTROPHYSIOLOGICAL EVALUATION OF THE EFFECTIVENESS OF NEUROFEEDBACK IN AMELIORATING CHRONIC POST-RAUMATIC STRESS DISORDER

The aim of our research was to evaluate the effectiveness of neurofeedback in reducing the symptoms of chronic Post Traumatic Stress Disorder (PTSD) in a patient who had developed the syndrome following a recurrence of sphenoid wing meningioma (SOM). EEG spectra and event-related potentials (ERPs) were used to construct an individual neurofeedback protocol and to provide objective monitoring of treatment efficacy. The patient, a 34-year-old female, was diagnosed with a sphenoid wing meningioma (SOM), which had been successfully operated. Three years later, however, the SOM had overgrown at the optic foramen and extended into the optic canal, and the patient had developed blurred vision. She was repeatedly operated, and recovered well. However, due to the recurrence she developed flashbacks, anxiety and sleep difficulties, such that she was unable to continue working in her profession. The symptoms had been occurring for 4 months. ERPs in a cued NOGO task, along with EEG spectra in the resting state and during task performance were used to assess brain functioning, providing the basis for a neurofeedback protocol. Twenty sessions of individually tailored neurofeedback were performed. The patient experienced a reduction of symptoms, accompanied by normalization of ERPs parameters. The results obtained in this case point to the possible benefits of individually tailored neurofeedback protocols in the treatment of PTSD.

The EEG signature of sensory evidence accumulation during decision formation closely tracks subjective perceptual experience

How neural representations of low-level visual information are accessed by higher-order processes to inform decisions and give rise to conscious experience is a longstanding question. Research on perceptual decision making has revealed a late event-related EEG potential (the Centro-Parietal Positivity, CPP) to be a correlate of the accumulation of sensory evidence. We tested how this evidence accumulation signal relates to externally presented (physical) and internally experienced (subjective) sensory evidence. Our results show that the known relationship between the physical strength of the external evidence and the evidence accumulation signal (reflected in the CPP amplitude) is mediated by the level of subjective experience of stimulus strength. This shows that the CPP closely tracks the subjective perceptual evidence, over and above the physically presented evidence. We conclude that a remarkably close relationship exists between the evidence accumulation process (i.e. CPP) and subjective perceptual experience, suggesting that neural decision processes and components of conscious experience are tightly linked.

Error-related negativity predicts failure in competitive dual-player video games.

Along with improvement in electroencephalogram (EEG)-measurement technology, limitations on the situations in which data can be recorded are gradually being overcome. EEG measurement in real environments has become increasingly important as a means to monitor brain activity in our daily lives, such as while playing consumer games in the living room. The present study measured brain EEG activity while two players engaged in a competitive consumer baseball game in conditions that closely resembled daily life. The recorded brain activity was thus likely related to natural mental reactions and cognitive function that occur in similar daily life activities. To measure the EEG from participants who freely moved while playing the game, we developed EEG devices that incorporated a wireless time synchronization system using Global Positioning Satellite (GPS) signals. These devices stamped the time obtained from the GPS signals onto each data sample, which was then used to synchronize the data that were recorded by different devices. When the batter in the game swung and missed, the error-related negativity component of the event-related EEG potential was strongly evoked in frontal electrodes of the participant controlling the batter. Furthermore, the error-related negativity was modulated according to who was winning and by how much. Thus, here we have demonstrated "real-world" brain activity using a competitive consumer game, which increases intrinsic participant motivation.