Cognitive Event-related Potentials Research Articles

Development and Validation of a Culturally Adapted, Event-related Potential Paradigm for Assessing Alcohol Cue Reactivity and Error Processing in Alcohol Dependence.

Research on event-related potentials (ERP) in addiction highlights the importance of cognitive ERP markers, such as P300 and error-related negativity (ERN), in distinguishing between alcohol-dependent patients and healthy controls. We aimed to develop and validate ERP paradigms utilizing culturally validated stimuli to evoke P300 and ERN for the Indian population. In a cross-sectional study, 16 alcohol-dependent patients and age-matched healthy controls were recruited. For P300, we designed a visual oddball (Go/No-Go) task using culturally appropriate alcohol and non-alcohol-related images. To study ERN, we used the Assessing Neurocognition via Gamified Experimental Logic (ANGEL) task, developed in India, integrating its "game" levels to capture error monitoring with fewer trials. A 32-channel EEG-ERP system was used for data acquisition. Participants showed high engagement in the visual Go/No-Go task, with 94.4% accuracy. The P300 difference wave showed significantly higher amplitudes (p = .01, Cohen's d = 0.97) and latencies (p < .001, Cohen's d = 1.62) in patients compared to controls at the Pz electrode. No significant group differences were found in accuracy or reaction times for frequent and rare stimuli. In the ANGEL task, patients had a significantly lower ERN difference wave amplitude at the Pz electrode than controls (p < .001, Cohen's d = 1.47), with no latency differences. Task accuracy was lower, and reaction time was longer in patients. The visual Go/No-Go task and the ANGEL task are promising tools for understanding the neurocognitive mechanisms underlying alcohol dependence in the Indian context.

Association of GAD1 gene polymorphism rs3749034 with the information processing and cognitive event-related potentials in schizophrenia patients and healthy subjects

ObjectiveGlutamic acid decarboxylase, an enzyme in GABA biosynthesis, is encoded by the GAD1 gene, the transcriptional activity of which is affected by the rs3749034 polymorphism. The aim was to investigate the effects of rs3749034 on cognitive event-related potentials (P300) in healthy subjects and schizophrenic patients. MethodsDetermination of rs3749034 polymorphism was performed in 89 healthy volunteers and 109 schizophrenic patients (males). Two-stimulus oddball task performance and P300 auditory evoked potentials were analyzed and patient symptomatology was assessed using the Positive and Negative Syndrome Scale (PANSS). ResultsAn increased frequency of C allele carriers was disclosed in patients. In controls, superior task performance was observed in cytosine-thymine carriers, while a greater P300 amplitude and shorter latency were found in C/C carriers. Analogous effects were found in patients with a disease onset before 25 years of age. Higher N5 and lower P3 and G5 PANSS scales were revealed in C/C homozygotes. ConclusionsThe findings substantiate an involvement of GABA-ergic mechanisms in maintaining an optimal excitatory-inhibitory balance and an association of rs3749034 with early-onset disorder and negative symptoms of schizophrenia. SignificanceThese results are important for understanding underlying mechanisms and the development of evidence-based methods for assessing the risk of schizophrenia.

Understanding the Pathophysiology of Mental Diseases and Early Diagnosis Thanks to Electrophysiological Tools: Some Insights and Empirical Facts.

Objective. Neurophysiological tools remain indispensable instruments in the assessment of psychiatric disorders. These techniques are widely available, inexpensive and well tolerated, providing access to the assessment of brain functional alterations. In the clinical psychiatric context, electrophysiological techniques are required to provide important information on brain function. While there is an immediate benefit in the clinical application of these techniques in the daily routine (emergency assessments, exclusion of organic brain alterations), these tools are also useful in monitoring the progress of psychiatric disorders or the effects of therapy. There is increasing evidence and convincing literature to confirm that electroencephalography and related techniques can contribute to the diagnostic workup, to the identification of subgroups of disease categories, to the assessment of long-term causes and to facilitate response predictions. Methods and Results. In this report we focus on 3 different novel developments of the use of neurophysiological techniques in 3 highly prevalent psychiatric disorders: (1) the value of EEG recordings and machine learning analyses (deep learning) in order to improve the diagnosis of dementia subtypes; (2) the use of mismatch negativity in the early diagnosis of schizophrenia; and (3) the monitoring of addiction and the prevention of relapse using cognitive event-related potentials. Empirical evidence was presented. Conclusion. Such information emphasized the important role of neurophysiological tools in the identification of useful biological markers leading to a more efficient care management. The potential of the implementation of machine learning approaches together with the conduction of large cross-sectional and longitudinal studies was also discussed.

Neurophysiological and neuropsychological parameters in patients with temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most common type of localization-related epilepsy (LRE) and has been extensively studied in the field of neuropsychology due to its significant association with cognitive impairments. Cognitive decline has long been recognized as a consequence of this form of epilepsy, with previous studies primarily focusing on neurophysiological measures. In this study, both neurophysiological and neuropsychological factors were analyzed in TLE patients compared to healthy control subjects. The Montreal Cognitive Assessment (MoCA) and Mini Mental State Examination (MMSE) tests were used to assess neuropsychological processes, while cognitive event-related potential (ERPs), particularly P300, were employed to analyze neurophysiological parameters. The study involved 21 TLE patients (mean age = 61.43) and 21 healthy control subjects. The results revealing that TLE patients scored significantly lower, indicating deficits in specific cognitive areas. The study also observed abnormalities in the ERPs, particularly in the assessment of P300 amplitude and latency, that may be indicative of underlying neural dysfunction related to attention and cognitive processing. In conclusion, the study provides compelling evidence of the association between TLE and a high incidence of cognitive deficits and decline. By considering both neurophysiological and neuropsychological factors, the study sheds light on the comprehensive impact of TLE on various cognitive domains and emphasizes the importance of early identification and management of cognitive impairments in TLE patients.

Machine Learning on Visibility Graph Features Discriminates the Cognitive Event-Related Potentials of Patients with Early Alzheimer's Disease from Healthy Aging.

We present a framework for electroencephalography (EEG)-based classification between patients with Alzheimer's Disease (AD) and robust normal elderly (RNE) via a graph theory approach using visibility graphs (VGs). This EEG VG approach is motivated by research that has demonstrated differences between patients with early stage AD and RNE using various features of EEG oscillations or cognitive event-related potentials (ERPs). In the present study, EEG signals recorded during a word repetition experiment were wavelet decomposed into 5 sub-bands (δ,θ,α,β,γ). The raw and band-specific signals were then converted to VGs for analysis. Twelve graph features were tested for differences between the AD and RNE groups, and t-tests employed for feature selection. The selected features were then tested for classification using traditional machine learning and deep learning algorithms, achieving a classification accuracy of 100% with linear and non-linear classifiers. We further demonstrated that the same features can be generalized to the classification of mild cognitive impairment (MCI) converters, i.e., prodromal AD, against RNE with a maximum accuracy of 92.5%. Code is released online to allow others to test and reuse this framework.

Immediate effects and duration of a short and single application of transcutaneous auricular vagus nerve stimulation on P300 event related potential.

Transcutaneous auricular vagus nerve stimulation (taVNS) is a neuromodulatory technique that stimulates the auricular branch of the vagus nerve. The modulation of the locus coeruleus-norepinephrine (LC-NE) network is one of the potential working mechanisms of this method. Our aims were 1-to investigate if short and single applications of taVNS can modulate the P300 cognitive event-related potential (ERP) as an indirect marker that reflects NE brain activation under control of the LC, and 2-to evaluate the duration of these changes. 20 healthy volunteers executed an auditory oddball paradigm to obtain P300 and reaction time (RT) values. Then a 7 min active or sham taVNS period was initiated and simultaneously a new P300 paradigm was performed. We successively repeated the paradigm on 4 occasions with different time intervals up to 56 min after the stimulation onset. During active taVNS an immediate and significant effect of increasing the amplitude and reducing the latency of P300, as well as a shortening in the RT was observed. This effect was prolonged in time up to 28 min. The values then returned to pre-stimulation levels. Sham stimulation did not generate changes. Our results, demonstrate differential facilitating effects in a concrete time window after taVNS. Literature about the modulatory effect of taVNS over P300 ERP shows a wide spread of results. There is not a standardized system for taVNS and currently the great heterogeneity of stimulation approaches concerning targets and parameters, make it difficult to obtain conclusions about this relationship. Our study was designed optimizing several stimulation settings, such as a customized earbud stimulator, enlarged stimulating surface, simultaneous stimulation over the cymba and cavum conchae, a Delayed Biphasic Pulse Burst and current controlled stimulation that adjusted the output voltage and guaranteed the administration of a preset electrical dose. Under our stimulation conditions, targeting vagal nerve fibers via taVNS modulates the P300 in healthy participants. The optimal settings of modulatory function of taVNS on P300, and their interdependency is insufficiently studied in the literature, but our data provides several easily optimizable parameters, that will produce more robust results in future.

Evaluation of Event-Related Potentials in Assessing Cognitive Functions of Adult Patients with Epilepsy of Unknown Etiology.

Cognitive impairment (CI) is an important consequence of epilepsy. The aim of the study was to assess cognitive performance in patients with epilepsy, using neuropsychological tests (NT) and event-related potentials (ERPs), with regard to demographic and clinical data. The study comprised 50 patients with epilepsy of unknown etiology and 46 healthy controls. Based on the NT results, the patients were divided into subgroups with/without CI. Parameters of P300 potential were compared between the patients and controls. P300 parameters and NT results were referred to demographics and clinical characteristics of epilepsy. Based on the NT, 66% of patients were assigned as cognitively impaired. Median P300 latency was significantly (p < 0.0002) prolonged in the study group. Subgroups of patients with and without CI significantly (p < 0.034) differed in education level and vocational activity, duration of epilepsy, age at its onset and frequency of polytherapy. P300 parameters showed significant (p < 0.03) relationships with duration of epilepsy, type and frequency of seizures and polytherapy. Cognitive impairment and ERPs abnormalities occur in a majority of patients with epilepsy of unknown etiology. Characteristics of epilepsy and socioeconomic status are related to cognitive performance. ERPs may complement neuropsychological methods in the assessment of cognition in patients with epilepsy.

Electrophysiological Correlates of Different Proactive Controls during Response Competition and Inhibition Tasks

The present study aims to investigate the behavioral outcomes and the antecedent brain dynamics during the preparation of tasks in which the discrimination is either about the choice (choice response task; CRT) or the action (Go/No-go), and in a task not requiring discrimination (simple response task; SRT). Using event-related potentials (ERPs), the mean amplitude over prefrontal, central, and parietal-occipital sites was analyzed in 20 young healthy participants in a time frame before stimulus presentation to assess cognitive, motor, and visual readiness, respectively. Behaviorally, participants were faster and more accurate in the SRT than in the CRT and the Go/No-go. At the electrophysiological level, the proactive cognitive and motor ERP components were larger in the CRT and the Go/No-go than the SRT, but the largest amplitude emerged in the Go/No-go. Further, the amplitude over parieto-occipital leads was enhanced in the SRT. The strongest intensity of the frontal negative expectancy wave over prefrontal leads in the Go/No-go task could be attributed to the largest uncertainty about the target presentation and subsequent motor response selection and execution. The enhanced sensory readiness in the SRT can be related to either an increased visual readiness associated with task requirements or a reduced overlap with proactive processing on the scalp.

The effect of disease severity and chronic CPAP-therapy on cognitive functions and event related potentials in OSAS.

<p>Obstructive sleep apnea syndrome (OSAS) may cause daytime sleepiness, mood changes and dysfunction in various cognitive areas due to recurrent arousals and / or chronic intermittent hypoxia. Different possibilities have been proposed regarding the most affected cognitive areas and mechanisms of OSAS. However, it is difficult to compare findings of the different studies due to the fact that individuals with different disease severities were included in the study groups. In the current study, we aimed to determine the relationship between severity of OSAS and cognitive functions, to investigate the effect of continuous positive airway pressure (CPAP) titration treatment on cognitive functions and the relationship between these changes and electrophysiological potential.&nbsp;</p>. <p>The study included 4 groups of patients with simple snoring and mild, mo&shy;de&shy;rate and severe OSAS. In the pre-treatment evaluations, verbal fluency, visuospatial me&shy;mory, attention, executive functions, lan&shy;guage abilities and electrophysiological tests for event-related potential were performed. The same procedure was reapplied after 4 months of CPAP-therapy.&nbsp;</p>. <p>Long-term recall scores and total word fluency scores were found to be low in the groups with moderate and severe disease compared to the patients with simple snoring (p: 0.04, p: 0.03, respectively). The information processing time was higher in patients with severe disease compared to patients with simple snoring (p: 0.02). The P200 and N100 latencies related to event related potentials (ERP) were significantly different between the groups (p: 0.004, p: 0.008, respectively). After CPAP treatment, significant differences were found in N100 amplitude and latencies and all cognitive areas except abstraction. In addition, N100 amplitude and latency change rate as well as change in attention and memory abilities were correlated (r: 0.72, p: 0.02; r: 0.57, p: 0.03, respectively).&nbsp;</p>. <p>In the current research, disease severity was found to negatively affect long-term logical memory, sustained attention and verbal fluency. Moreover, significant improvement was detected in all cognitive areas with CPAP treatment. The findings of our study support that changes in N100 potential have the potential to be used as a biomarker that can be used to monitor cognitive function recovery after treatment.</p>.

Cortical Brain Perfusion and Cognitive Event Related Potentials in Patients with Psychomotor Retardation in Late Onset Depression.

Late onset depression is characterised by pronounced cognitive impairment, more somatic complaints and psychomotor retardation. Psychomotor slowing may be due to impairment in either motor or cognitive domain. Electrophysiology may be particularly convenient as a tool in studies of psychomotor retardation, as it can separate central cognitive processing from the motor processing. In this study we compared event related potentials (ERP) in the two groups of patients with late onset depression and psychomotor slowing as measured by reaction time (RT): a group of patients with lower RT was compared to a group with a higher RT. Twenty patients with late onset depression were included in the study after they had reached remission. Four weeks after reaching remission patients were reevaluated clinically using Hamilton Depression Rating Scale, Mini Mental State Examination, and with a computer version of the Stroop task. ERP, accuracy and RTs were simultaneously recorded. Both groups of patients aditionaly underwent a perfusion SPECT imaging. There were no differences between the short and long RT groups of patients in amplitudes of the late positive Stroop related potentials. The group of patients with longer RTs showed significant hyperperfusion in precentral gyrus, parietal regions, cuneus and hypoperfusion within insular, frontal, temporal and limbic (parahyppocampal gyrus and anterior cingulate) cortices, as well as cerebellum. We found no ERP differences between the two groups suggesting that although patients may differ on psychomotor retardation measured as RT, their cognitive abilities may be quite similar. Perfusion SPECT imaging however revealed a significant difference between them. This may be due to a process of compensation and applying different strategies to cope with cognitive impairment in the two groups.

Description and Outcome of Severe Hypoglycemic Encephalopathy in the Intensive Care Unit.

Disorders of consciousness due to severe hypoglycemia are rare but challenging to treat. The aim of this retrospective cohort study was to describe our multimodal neurological assessment of patients with hypoglycemic encephalopathy hospitalized in the intensive care unit and their neurological outcomes. Consecutive patients with disorders of consciousness related to hypoglycemia admitted for neuroprognostication from 2010 to 2020 were included. Multimodal neurological assessment included electroencephalography, somatosensory and cognitive event-related potentials, and morphological and quantitative magnetic resonance imaging (MRI) with quantification of fractional anisotropy. Neurological outcomes at 28days, 3months, 6months, 1year, and 2years after hypoglycemia were retrieved. Twenty patients were included. After 2years, 75% of patients had died, 5% remained in a permanent vegetative state, 10% were in a minimally conscious state, and 10% were conscious but with severe disabilities (Glasgow Outcome Scale-Extended scores 3 and 4). All patients showed pathologic electroencephalography findings with heterogenous patterns. Morphological brain MRI revealed abnormalities in 95% of patients, with various localizations including cortical atrophy in 65% of patients. When performed, quantitative MRI showed decreased fractional anisotropy affecting widespread white matter tracts in all patients. The overall prognosis of patients with severe hypoglycemic encephalopathy was poor, with only a small fraction of patients who slowly improved after intensive care unit discharge. Of note, patients who did not improve during the first 6months did not recover consciousness. This study suggests that a multimodal approach capitalizing on advanced brain imaging and bedside electrophysiology techniques could improve diagnostic and prognostic performance in severe hypoglycemic encephalopathy.

EEG reveals deficits in sensory gating and cognitive processing in asymptomatic adults with a history of concussion

ABSTRACT Objective Individuals with a concussion history tend to perform worse on dual-tasks compared controls but the underlying neural mechanisms contributing to these deficits are not understood. This study used event-related potentials (ERPs) to investigate sensory gating and cognitive processing in athletes with and without a history of concussion while they performed a challenging dual-task. Methods We recorded sensory (P50, N100) and cognitive (P300) ERPs in 30 athletes (18 no previous concussion; 12 history of concussion) while they simultaneously performed an auditory oddball task and a working memory task that progressively increased in difficulty. Results The concussion group had reduced auditory performance as workload increased compared to the no-concussion group. Sensory gating and cognitive processing were reduced in the concussion group indicating problems with filtering relevant from irrelevant information and appropriately allocating resources. Sensory gating (N100) was positively correlated with cognitive processing (P300) at the hardest workload in the no-concussion group but negatively correlated in the concussion group. Conclusion Concussions result in long-term problems in behavioral performance, which may be due to poorer sensory gating that impacts cognitive processing. Significance Problems effectively gating sensory information may influence the availability or allocation of attention at the cognitive stage in those with a concussion.

Resolving the mesoscopic missing link: Biophysical modeling of EEG from cortical columns in primates

Event-related potentials (ERP) are among the most widely measured indices for studying human cognition. While their timing and magnitude provide valuable insights, their usefulness is limited by our understanding of their neural generators at the circuit level. Inverse source localization offers insights into such generators, but their solutions are not unique. To address this problem, scientists have assumed the source space generating such signals comprises a set of discrete equivalent current dipoles, representing the activity of small cortical regions. Based on this notion, theoretical studies have employed forward modeling of scalp potentials to understand how changes in circuit-level dynamics translate into macroscopic ERPs. However, experimental validation is lacking because it requires in vivo measurements of intracranial brain sources. Laminar local field potentials (LFP) offer a mechanism for estimating intracranial current sources. Yet, a theoretical link between LFPs and intracranial brain sources is missing. Here, we present a forward modeling approach for estimating mesoscopic intracranial brain sources from LFPs and predict their contribution to macroscopic ERPs. We evaluate the accuracy of this LFP-based representation of brain sources utilizing synthetic laminar neurophysiological measurements and then demonstrate the power of the approach in vivo to clarify the source of a representative cognitive ERP component. To that end, LFP was measured across the cortical layers of visual area V4 in macaque monkeys performing an attention demanding task. We show that area V4 generates dipoles through layer-specific transsynaptic currents that biophysically recapitulate the ERP component through the detailed forward modeling. The constraints imposed on EEG production by this method also revealed an important dissociation between computational and biophysical contributors. As such, this approach represents an important bridge between laminar microcircuitry, through the mesoscopic activity of cortical columns to the patterns of EEG we measure at the scalp.

Cognitive screening in HTLV-1-infected people using a self-perceived memory score and auditory P300.

The HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is the most common neurological manifestation associated with human T-cell lymphotropic virus type-1 (HTLV-1) infection. Although cognitive impairment has been highlighted in the spectrum of HTLV-1 neurological manifestations, it may go unnoticed in those who do not spontaneously report it. We aimed at evaluating the applicability of a self-perceived memory score (SMS) and the cognitive event-related potential (P300) for early detection of cognitive impairment in HTLV-1-infected people. The SMS was measured by a 0-10 point numeric scale combined with a sad-happy face rating scale. The higher the number, the better was the SMS. The P300 was obtained through an oddball paradigm with a mental counting task. The participants were 15 (21.4%) individuals with HAM/TSP, 20 (28.6%) HTLV-1 asymptomatic carriers, and 35 (50%) seronegative controls. We found that SMS (p < 0.001) and P300 latency (p < 0.001) got progressively worse from the seronegative controls to the asymptomatic carriers and then to the HAM/TSP. The results that indicated cognitive impairment were SMS < 7.2 points and P300 latency > 369.0ms. The HAM/TSP group showed the highest prevalence of altered P300 (80%) and SMS (87%). Interestingly, the asymptomatic group also presented significantly higher prevalence of altered SMS (60%) and P300 (35%) when compared to controls (< 10%). The frequency of cognitive impairment was 16 times higher in the HTLV-1 asymptomatic group and 69 times higher in the HAM/TSP group when compared to controls. The use of SMS in the medical consultation was a useful and easy-to-apply method to screen HTLV-1-infected subjects for everyday memory complaints.

Using Cognitive Event-Related Potentials in the Management of Alcohol Use Disorder: Towards an Individual Approach

Using Cognitive Event-Related Potentials in the Management of Alcohol Use Disorder: Towards an Individual Approach

Transcutaneous auricular vagus nerve stimulation cannot modulate the P3b event-related potential in healthy volunteers

ObjectiveThe release of cortical norepinephrine is one of the possible mechanisms of action of vagus nerve stimulation (VNS), a neuromodulatory treatment currently under investigation for cognitive impairment. Transcutaneous auricular VNS (taVNS) may be able to activate vagal nerve branches ending in the brainstem’s locus coeruleus (LC) non-invasively. The aim was to investigate if acute taVNS can modulate the P3b, a cognitive event-related potential (ERP) reflecting noradrenergic brain activation under control of the LC. MethodsThirty-nine healthy volunteers performed an auditory oddball task during no stimulation, sham stimulation and taVNS in a randomized order. P3b amplitude, latency and behavioral outcome parameters were compared between conditions using linear mixed models. ResultsP3b amplitude and latency during taVNS did not differ significantly from sham or control. Reaction time shortened and P3b latency prolonged with repetition of the oddball task. ConclusionsWe were unable to modulate cognitive ERPs by means of acute taVNS in a large group of healthy volunteers. SignificanceTargeting vagal nerve fibres via a transcutaneous approach did not alter the P3b in healthy participants. The stimulation parameters used and transient delivery of taVNS might be insufficient to adequately modulate the LC. Also, a disbalanced locus coeruleus - norepinephrine system in patients may be more prone for improvement.

Genetic association of APOE epsilon2 genotype with neurophysiological characteristics in healthy adults

AbstractBackgroundThe association of apolipoprotein E genotype with late‐onset AD (LOAD) is well established. APOE e4 allele is the major common risk factor for LOAD (Saunders et al., 1993), and the rare APOE e2 allele appears to confer protective effect for LOAD (Goldberg et al., 2020). The mechanisms underlying the impact of the APOE e2 allele on LOAD development remain largely unknown. The study was aimed at determining the possible APOE e2 genotype effect on EEG and cognitive event‐related potentials (ERP) in non‐demented adults.MethodThe enrolled cohort included 135 healthy volunteers, age range 20‐69 years, stratified by APOE genotype. APOE e2/e3 subgroup included 21 subjects, APOE e3/e3 subgroup ‐ 76 subjects, APOE e4/e3 subgroup ‐ 38 subjects. Informed written consent was obtained from all participants. All subjects underwent a neurological examination and cognitive screening. The significance of the differences between the EEG and cognitive ERP characteristics in different subgroups was estimated using ANOVA in the general linear modelResultThe presence of the APOE e2/e3 genotype was associated with higher individual alpha peak frequency (IAPF) relative to the presence of APOE e3/e3 and APOE e4/e3 genotypes. IAPF a stable neurophysiological 'trait' marker which has been shown to correlate with better memory scores (Grandy et al., 2013). In the carriers of APOE e2 allele P300 latency remained stable during aging, while in the carriers of APOE e3/e3 as well as APOE e4/e3 genotypes P300 latency showed positive correlation with age.ConclusionAPOE e2 genotype is associated with higher EEG IAPF and stable P300 latency during aging that can underlie better cognitive reserve and protective effect against LOAD. The effect may be related to larger hippocampal volume and better maintenance of neuronal connections in APOE e2 healthy carriers compared to non‐carriers.

Cognitive assessment using ERP in child and adolescent psychiatry: Difficulties and opportunities

Event related potentials (ERPs) represent powerful tools to investigate cognitive functioning in child and adolescent psychiatry. So far, the available body of research has largely focused on advancements in analysis methods, with little attention given to the perspective of assessment. The aim of this brief report is to provide recommendations for cognitive ERPs assessment that can be applied across diagnostic categories in child and adolescent psychiatry research. First, we discuss major issues for ERPs testing using examples from common psychiatric disorders. We conclude by summing up our recommendations for methodological standards and highlighting the potential role of ERPs in the field.

Single-Trial Detection of Event-Related Potentials with Integral Shape Averaging: An Application to the Elusive N400.

The estimation of Event-Related Potentials (ERPs) from the ambient EEG is a difficult task, usually achieved through the synchronous averaging of an extensive series of trials. However, this technique has some caveats: the ERPs have to be strictly time-locked with similar shape, i.e. emitted with the same latency and the same profile, with minor fluctuations of their amplitudes. Also, the method requires a huge number of valid trials (~100) to efficiently raise the ERPs from the EEG trials. In the case of cognitive ERPs, as with the N400, the delivered stimulus has to be different for each trial, the latencies are varying, and the number of available trials is usually low. In this paper, an alternative method, coined Integral Shape Averaging (ISA) and its derivatives are detailed. ISA is robust to varying latencies and affine transforms of shape. Furthermore, a new method coined ISAD can be derived to extract ERPs even from a single trial experiment. The aim here is to illustrate the potential of ISAD for N400 component extraction on real EEG data, with emphasis on its general applicability for ERPs computation and its major assets like reduced experimental protocol. Some insights are also given on its potential use to study ERP variability, through shape and latency.Clinical Relevance- The proposed algorithm aims to be a helpful tool in clinical practice to analyze and interpret evoked responses in real experimental settings, especially for particularities in neurology.

Pathways of perceptual primacy: ERP evidence for relationships between autism traits and enhanced perceptual functioning

Autistic individuals show enhanced perceptual functioning on many behavioral tasks. Neurophysiological evidence also supports the conclusion that autistic individuals utilize perceptual processes to a greater extent than neurotypical comparisons to support problem solving and reasoning; however, how atypicalities in early perceptual processing influence subsequent cognitive processes remains to be elucidated. The goals of the present study were to test the relationship between early perceptual and subsequent cognitive event related potentials (ERPs) and their relationship to levels of autism traits. 62 neurotypical adults completed the Autism Spectrum Quotient (AQ) and participated in an ERP task. Path models were compared to test predictive relationships among an early perceptual ERP (the P1 component), a subsequent cognitive ERP (the N400 effect), and the Attention to Detail subscale of the AQ. The size of participants' P1 components was positively correlated with the size of their N400 effect and their Attention to Detail score. Model comparisons supported the model specifying that variation in Attention to Detail scores predicted meaningful differences in participants’ ERP waveforms. The relationship between Attention to Detail scores and the size of the N400 effect was significantly mediated by the size of the P1 effect. This study revealed that neurotypical adults with higher levels of Attention to Detail show larger P1 differences, which, in turn, correspond to larger N400 effects. Findings support the Enhanced Perceptual Functioning model of autism, suggesting that early perceptual processing differences may cascade forward and result in modifications to later cognitive mechanisms.