Topographical and temporal stability of the P300

EEG Dataset for RSVP and P300 Speller Brain-Computer Interfaces

As attention to deep learning techniques has grown, many researchers have attempted to develop ready-to-go brain-computer interfaces (BCIs) that include automatic processing pipelines. However, to do so, a large and clear dataset is essential to increase the model's reliability and performance. Accordingly, our electroencephalogram (EEG) dataset for rapid serial visual representation (RSVP) and P300 speller may contribute to increasing such BCI research. We validated our dataset with respect to features and accuracy. For the RSVP, the participants (N = 50) achieved about 92% mean target detection accuracy. At the feature level, we observed notable ERPs (at 315 ms in the RSVP; at 262 ms in the P300 speller) during target events compared to non-target events. Regarding P300 speller performance, the participants (N = 55) achieved about 92% mean accuracy. In addition, P300 speller performance over trial repetitions up to 15 was explored. The presented dataset could potentially improve P300 speller applications. Further, it may be used to evaluate feature extraction and classification algorithm effectively, such as for cross-subjects/cross-datasets, and even for the cross-paradigm BCI model.

Internal consistency reliability of the P300 to novelty in infants: The influence of trial number and data loss due to artifacts

The P300 is an event-related potential component that reflects attention to motivationally salient stimuli and may be a promising tool to examine individual differences in cognitive-affective processing very early in development. However, the psychometric properties of the P300 in infancy are unknown, a fact that limits the component's utility as an individual difference measure in developmental research. To address this gap, 38 infants completed an auditory three-stimulus oddball task that included frequent standard, infrequent deviant, and novel stimuli. We quantified the P300 at a single electrode site and at region of interest (ROI) and examined the internal consistency reliability of the component, both via split-half reliability and as a function of trial number. Results indicated that the P300 to standard, deviant, and novel stimuli fell within moderate to high internal consistency reliability thresholds, and that scoring the component at an ROI led to slightly higher estimates of reliability. However, the percentage of data loss due to artifacts increased across the course of the task, suggesting that including more trials will not necessarily improve the reliability of the P300. Together, these results suggest that robust and reliable measurement of the P300 will require designing tasks that minimize trial number and maximize infant tolerability.

P300 Speller Performance Predictor Based on RSVP Multi-feature

Brain-computer interface (BCI) systems were developed so that people can control computers or machines through their brain activity without moving their limbs. The P300 speller is one of the BCI applications used most commonly, as is very simple and reliable and can achieve satisfactory performance. However, like other BCIs, the P300 speller still has room for improvements in terms of its practical use, for example, selecting the best compromise between spelling accuracy and information transfer rate (ITR; speed) so that the P300 speller can maintain high accuracy while increasing spelling speed. Therefore, seeking correlates of, and predicting, the P300 speller's performance is necessary to understand and improve the technique. In this work, we investigated the correlations between rapid serial visual presentation (RSVP) task features and the P300 speller's performance. Fifty-five subjects participated in the RSVP and conventional matrix P300 speller tasks and RSVP behavioral and electroencephalography (EEG) features were compared in the P300's speller performance. We found that several of the RSVP's event-related potential (ERP) and behavioral features were correlated with the P300 speller's offline binary classification accuracy. Using these features, we propose a simple multi-feature performance predictor (r = 0.53, p = 0.0001) that outperforms any single feature performance predictor, including that of the conventional RSVP T1% predictor (r = 0.28, p = 0.06). This result demonstrates that selective multi-features can predict BCI performance better than a single feature alone.

Sympathovagal imbalance and neurophysiologic cognitive assessment using evoked potentials in polycystic ovary syndrome in young adolescents - a cross-sectional study

Background Altered lifestyle and urbanization have potentially increased the prevalence of polycystic ovary syndrome (PCOS) among the women in India. The aim of the present study was to evaluate the autonomic function and subclinical cognition impairment using evoked potentials in PCOS-affected young adolescents. Methods This was a cross-sectional study, approved by Indian Medical of Council Research as a short-term student project. The study was performed with adolescent girls (age group, 10-18 years) diagnosed as having PCOS, attending the Department of Obstetrics and Gynecology at Sri Manakula Vinayagar Medical College and Hospital, Puducherry. Autonomic function was evaluated using heart rate variability and cognition employing auditory evoked potentials (P300 latency and amplitude) among the control group (n=30) and the PCOS group (n=30). Results Our study reports indicated that autonomic functions were significantly affected among the PCOS group compared to the control group (p=0.03), with sympathetic dominance and decreased vagal tone. P300 latency was prolonged and amplitude was decreased among the PCOS group, but the results were not statistically significant when compared to the control group. Body mass index showed significant correlation with sympathovagal imbalance. Conclusion The study indicates that autonomic functions are significantly altered in the PCOS group. Subclinical cognition impairment is seen among the PCOS group but is not pronounced enough to be proven statistically. This study informs adolescent girls to make early lifestyle changes as soon as possible before any significant clinical impairment occurs.

The Startle-Evoked Potential: Negative Affect and Severity of Pathology in Anxiety/Mood Disorders

BACKGROUND

The National Institute of Mental Health Research Domain Criteria initiative encourages a search for dimensional biological measures of psychopathology unconstrained by current diagnostic categories. Consistent with this aim, the presented research studies a large sample of anxiety and mood disorder patients, assessing differences in principal diagnoses and comorbidity patterns, clinicians' ratings, and questionnaire measures of negative affect and life dysfunction as they relate to a potential brain marker of pathology: the amplitude of the event-related potential (ERP) elicited by a startle-evoking stimulus.

METHODS

Patients seeking evaluation or treatment for anxiety and mood disorders (N = 208) participated in two tasks at the University of Florida (Gainesville, FL): 1) imagining emotional and neutral events and 2) viewing emotional and neutral pictures while acoustic startle probes were presented and the ERP was recorded. For a comparison patient group (N = 120), startle probes were administered and ERPs recorded at the University of Greifswald (Greifswald, Germany) while performing the same imagery task.

RESULTS

Reduced positive amplitude of a centroparietal startle-evoked ERP (156-352 ms after onset) significantly predicted higher questionnaire scores of anxiety/depression, reports of increased life dysfunction, greater comorbidity, and clinician ratings of heightened severity and poorer prognosis. The effect was general across principal diagnoses, found for both the Florida and German samples, and consistent in pattern despite differences in the tasks administered.

CONCLUSIONS

The startle-evoked ERP reliably predicts severity and breadth of psychopathology, independent of task context. It is a potential significant contributor to a needed array of biological measures that might improve classification of anxiety and mood disorders.

Auditory evoked potential P300 in adults: reference values

OBJECTIVE

To establish reference intervals for cognitive potential P300 latency using tone burst stimuli.

METHODS

This study involved 28 participants aged between 18 and 59 years. P300 recordings were performed using a two-channel device (Masbe, Contronic). Electrode placement was as follows: Fpz (ground electrode), Cz (active electrode), M1 and M2 (reference electrodes). Intensity corresponded to 80 dB HL and frequent and rare stimulus frequencies to 1,000Hz and 2,000Hz, respectively. Stimuli were delivered binaurally.

RESULTS

Mean age of participants was 35 years. Average P300 latency was 305ms.

CONCLUSION

Maximum acceptable P300 latency values of 362.5ms (305 + 2SD 28.75) were determined for adults aged 18 to 59 years using the protocol described.

OBJETIVO

Estabelecer valores de referência para a latência do potencial cognitivo P300 com estímulos tone burst.

MÉTODOS

Participaram do estudo 28 indivíduos entre 18 e 59 anos. O registro do P300 foi realizado no equipamento Masbe da marca Contronic. Os eletrodos foram fixados nas posições Fpz (eletrodo terra), Cz (eletrodo ativo), M1 e M2 (eletrodos referência). A intensidade foi de 80 dB NA. A frequência do estímulo frequente foi de 1.000Hz e a do estímulo raro de 2.000Hz. Os estímulos foram apresentados na forma binaural.

RESULTADOS

A média de idade dos indivíduos foi de 35 anos. A média de latência para P300 de 305ms.

CONCLUSÃO

Usando o protocolo descrito, o valor máximo de latência aceitáveis para P300 foram de 362,5ms (305 + 2DP 28,75) na faixa etária do adulto de 18 a 59 anos.

Contralateral Noise Stimulation Delays P300 Latency in School-Aged Children

Background and Objective

The auditory cortex modulates auditory afferents through the olivocochlear system, which innervates the outer hair cells and the afferent neurons under the inner hair cells in the cochlea. Most of the studies that investigated the efferent activity in humans focused on evaluating the suppression of the otoacoustic emissions by stimulating the contralateral ear with noise, which assesses the activation of the medial olivocochlear bundle. The neurophysiology and the mechanisms involving efferent activity on higher regions of the auditory pathway, however, are still unknown. Also, the lack of studies investigating the effects of noise on human auditory cortex, especially in peadiatric population, points to the need for recording the late auditory potentials in noise conditions. Assessing the auditory efferents in schoolaged children is highly important due to some of its attributed functions such as selective attention and signal detection in noise, which are important abilities related to the development of language and academic skills. For this reason, the aim of the present study was to evaluate the effects of noise on P300 responses of children with normal hearing.

Methods

P300 was recorded in 27 children aged from 8 to 14 years with normal hearing in two conditions: with and whitout contralateral white noise stimulation.

Results

P300 latencies were significantly longer at the presence of contralateral noise. No significant changes were observed for the amplitude values.

Conclusion

Contralateral white noise stimulation delayed P300 latency in a group of school-aged children with normal hearing. These results suggest a possible influence of the medial olivocochlear activation on P300 responses under noise condition.

Minimized extracorporeal circulation does not impair cognitive brain function after coronary artery bypass grafting

OBJECTIVES

Objective evaluation of the impact of minimized extracorporeal circulation (MECC) on perioperative cognitive brain function in coronary artery bypass grafting (CABG) by electroencephalogram P300 wave event-related potentials and number connection test (NCT) as metrics of cognitive function.

METHODS

Cognitive brain function was assessed in 31 patients in 2013 with a mean age of 65 years [standard deviation (SD) 10] undergoing CABG by the use of MECC with P300 auditory evoked potentials (peak latencies in milliseconds) directly prior to intervention, 7 days after and 3 months later. Number connection test, serving as method of control, was performed simultaneously in all patients.

RESULTS

Seven days following CABG, cognitive P300 evoked potentials were comparable with preoperative baseline values [vertex (Cz) 376 (SD 11) ms vs 378 (18) ms, P = 0.39; frontal (Fz) 377 (11) vs 379 (21) ms, P = 0.53]. Cognitive brain function at 3 months was compared with baseline values [(Cz) 376 (11) ms vs 371 (14 ms) P = 0.09; (Fz) 377 (11) ms vs 371 (15) ms, P = 0.04]. Between the first postoperative measurement and 3 months later, significant improvement was observed [(Cz) 378 (18) ms vs 371 (14) ms, P = 0.03; (Fz) 379 (21) vs 371 (15) ms, P = 0.02]. Similar clearly corresponding patterns could be obtained via the number connection test. Results could be confirmed in repeated measures analysis of variance for Cz (P = 0.05) and (Fz) results (P = 0.04).

CONCLUSIONS

MECC does not adversely affect cognitive brain function after CABG. Additionally, these patients experience a substantial significant cognitive improvement after 3 months, evidentiary proving that the concept of MECC ensures safety and outcome in terms of brain function.

P300 in obsessive-compulsive disorder: source localization and the effects of treatment

Converging evidence suggests that frontostriatal abnormalities underlie OCD symptoms. The event-related potential P300 is generated along a widely distributed network involving several of the areas implicated in OCD. P300 abnormalities reported in patients with OCD suggest increased activity in these areas. The aim of the present study was to investigate this assumption in unmedicated patients with OCD, and to assess the effects of OCD treatment on P300 brain activity patterns. Seventy-one unmedicated patients with a DSM-IV diagnosis of OCD and 71 age- and gender-matched healthy control subjects participated in the study. The P300 was obtained through 32-channel EEG during an auditory oddball paradigm. Forty-three patients underwent a second EEG assessment after treatment with sertraline and behavioural therapy. Low-resolution electromagnetic tomography (LORETA) was used to localize the sources of brain electrical activity.

RESULTS

Increased P300-related activity was observed predominantly in the left orbitofrontal cortex, but also in left prefrontal, parietal and temporal areas, in patients compared to controls at baseline. After treatment, reduction of left middle frontal cortex hyperactivity was observed in patients.

CONCLUSIONS

Findings of increased activity in frontoparietal areas in patients are consistent with several previous studies. Importantly, OCD treatment led to reduction of hyperactivity in the left middle frontal cortex, an area associated with context processing and uncertainty that might be important for the emergence of OCD symptoms. Thus, the present study is the first to show an association between P300 abnormalities and activity in brain regions postulated to be involved in the pathophysiology of OCD.

Retest reliability of individual p3 topography assessed by high density electroencephalography

BACKGROUND

Some controversy remains about the potential applicability of cognitive potentials for evaluating the cerebral activity associated with cognitive capacity. A fundamental requirement is that these neurophysiological parameters show a high level of stability over time. Previous studies have shown that the reliability of diverse parameters of the P3 component (latency and amplitude) ranges between moderate and high. However, few studies have paid attention to the retest reliability of the P3 topography in groups or individuals. Considering that changes in P3 topography have been related to different pathologies and healthy aging, the main objective of this article was to evaluate in a longitudinal study (two sessions) the reliability of P3 topography in a group and at the individual level.

RESULTS

The correlation between sessions for P3 topography in the grand average of groups was high (r = 0.977, p<0.001). The within-subject correlation values ranged from 0.626 to 0.981 (mean: 0.888). In the between-subjects topography comparisons, the correlation was always lower for comparisons between different subjects than for within-subjects correlations in the first session but not in the second session.

CONCLUSIONS

The present study shows that P3 topography is highly reliable for group analysis (comprising the same subjects) in different sessions. The results also confirmed that retest reliability for individual P3 maps is suitable for follow-up studies for a particular subject. Moreover, P3 topography appears to be a specific marker considering that the between-subjects correlations were lower than the within-subject correlations. However, P3 topography appears more similar between subjects in the second session, demonstrating that is modulated by experience. Possible clinical applications of all these results are discussed.

Neuroscientific measures of covert behavior

In radical behaviorism, the difference between overt and covert responses does not depend on properties of the behavior but on the sensitivity of the measurement tools employed by the experimenter. Current neuroscientific research utilizes technologies that allow measurement of variables that are undetected by the tools typically used by behavior analysts. Data from a specific neuroscientific technique, event-related potential (ERP), suggest that emission of otherwise covert responses can be indexed and that such covert responses are sensitive to stimulus control and selection by consequences. The P3 ERP effect is proposed as indicative of emission. Moreover, ERP results in semantic priming experiments suggest that operants are sensitive to changes in stimulus control even when they are not emitted (latent responses). Changes in response strength of latent responses as a function of stimulus control can in fact be measured by reaction time data and an ERP dependent variable called the N400 effect. If the interpretations provided in this paper are accurate, an index of covertly emitted operants (P3 effect) constitutes experimental evidence suggesting the validity of a Skinnerian radical behaviorist perspective on behavior. Moreover, in a Skinnerian paradigm, measured fluctuations in the response strength of latent operants as a function of environmental changes (N400 effect) would validate Palmer's (2009) concept of the repertoire.

Effects of GSM signals during exposure to event related potentials (ERPs)

OBJECTIVES

The primary aim of this work was to assess the effect of electromagnetic field (EMF) from the GSM mobile phone system on human brain function. The assessment was based on the assay of event related potentials (ERPs).

MATERIAL AND METHODS

The study group consisted of 15 volunteers, including 7 men and 8 women. The test protocol comprised determination of P300 wave in each volunteer during exposure to the EMF. To eliminate possible effects of the applied test procedure on the final result, the test was repeated without EMF exposure. P300 latency, amplitude, and latency of the N1, N2, P2 waves were analysed.

RESULTS

The statistical analysis revealed an effect of EMF on P300 amplitude. In the experiment with EMF exposure, lower P300 amplitudes were observed only at the time in which the volunteers were exposed to EMF; when the exposure was discontinued, the values of the amplitude were the same as those observed before EMF application. No such change was observed when the experiment was repeated with sham exposure, which may be considered as an indirect proof that lower P300 amplitude values were due to EMF exposure. No statistically significant changes were noted in the latencies of the N1, N2, P2 waves that precede the P300 wave, nor in the latency of the P300 itself.

CONCLUSIONS

The results suggest that exposure to GSM EMF exerts some effects on CNS, including effects on long latency ERPs.

Neurophysiological measures of sensory registration, stimulus discrimination, and selection in schizophrenia patients

Cortical Neurophysiological event related potentials (ERPs) are multidimensional measures of information processing that are well suited to efficiently parse automatic and controlled components of cognition that span the range of deficits exhibited in schizophrenia patients. Components following a stimulus reflect the sequence of neural processes triggered by the stimulus, beginning with early automatic sensory processes and proceeding through controlled decision and response related processes. Previous studies employing ERP paradigms have reported deficits of information processing in schizophrenia across automatic through attention dependent processes including sensory registration (N1), automatic change detection (MMN), the orienting or covert shift of attention towards novel or infrequent stimuli (P3a), and attentional allocation following successful target detection processes (P3b). These automatic and attention dependent information components are beginning to be recognized as valid targets for intervention in the context of novel treatment development for schizophrenia and related neuropsychiatric disorders. In this review, we describe three extensively studied ERP components (N1, mismatch negativity, P300) that are consistently deficient in schizophrenia patients and may serve as genetic endophenotypes and as quantitative biological markers of response outcome.

The effects of immediate and short-term retest on the latencies and amplitudes of the auditory event-related potentials in healthy adults

OBJECTIVE

To evaluate the immediate and short-term effects of repeated within session trials on N1, P2, N2 and P3 latencies and P2, N2 and P3 amplitudes in healthy adults.

MATERIALS AND METHODS

ERPs were elicited by the auditory oddball paradigm and recorded over Fz, Cz and Pz in 18 healthy adults over two sessions, one to three days apart, and two within session trials with one to three minutes trial-retrial interval. The ERPs' latencies and amplitudes were blindly calculated and were analyzed by Analysis of Variance (ANOVA) with repeated measures.

RESULTS

Significant decreases of N2 amplitude at Fz, P3 amplitude at Cz and P3 latency at Pz were recorded in the second-compared to the first within session trial (p=0.034, 0.041, 0.046, respectively). There were no significant inter-session differences regarding N1, P2, N2 and P3 latencies or amplitudes. There was no significant interaction between session and trial. A statistically significant difference was found between the first session's mental count errors (p=0.039) but there were no significant differences between the second session's trials (p=0.581) or between sessions (p=0.328).

CONCLUSIONS

N1, P2, N2 and P3 latencies and amplitudes are stable at short-term intervals of one to three days, but one to three minutes' retrial interval may affect P3 latency and N2 and P3 amplitudes. We suggest that when primary novelty-induced cognitive processes are evaluated, single trial sessions or more than three-minute inter-trials interval should be employed in order to mitigate habituation.

Updating P300: an integrative theory of P3a and P3b

The empirical and theoretical development of the P300 event-related brain potential (ERP) is reviewed by considering factors that contribute to its amplitude, latency, and general characteristics. The neuropsychological origins of the P3a and P3b subcomponents are detailed, and how target/standard discrimination difficulty modulates scalp topography is discussed. The neural loci of P3a and P3b generation are outlined, and a cognitive model is proffered: P3a originates from stimulus-driven frontal attention mechanisms during task processing, whereas P3b originates from temporal-parietal activity associated with attention and appears related to subsequent memory processing. Neurotransmitter actions associating P3a to frontal/dopaminergic and P3b to parietal/norepinephrine pathways are highlighted. Neuroinhibition is suggested as an overarching theoretical mechanism for P300, which is elicited when stimulus detection engages memory operations.

Updating P300: an integrative theory of P3a and P3b

The empirical and theoretical development of the P300 event-related brain potential (ERP) is reviewed by considering factors that contribute to its amplitude, latency, and general characteristics. The neuropsychological origins of the P3a and P3b subcomponents are detailed, and how target/standard discrimination difficulty modulates scalp topography is discussed. The neural loci of P3a and P3b generation are outlined, and a cognitive model is proffered: P3a originates from stimulus-driven frontal attention mechanisms during task processing, whereas P3b originates from temporal-parietal activity associated with attention and appears related to subsequent memory processing. Neurotransmitter actions associating P3a to frontal/dopaminergic and P3b to parietal/norepinephrine pathways are highlighted. Neuroinhibition is suggested as an overarching theoretical mechanism for P300, which is elicited when stimulus detection engages memory operations.

Hemispheric differences in hemodynamics elicited by auditory oddball stimuli

Evidence from neuroimaging studies suggests that the right hemisphere of the human brain might be more specialized for attention than the left hemisphere. However, differences between right and left hemisphere in the magnitude of hemodynamic activity (i.e., 'functional asymmetry') rarely have been explicitly examined in previous neuroimaging studies of attention. This study used a new voxel-based comparison method to examine hemispheric differences in the amplitude of the hemodynamic response in response to infrequent target, infrequent novel, and frequent standard stimuli during an event-related fMRI auditory oddball task in 100 healthy adult participants. Processing of low probability task-relevant target stimuli, or 'oddballs', and low probability task-irrelevant novel stimuli is believed to engage in orienting and attentional processes. It was hypothesized that greater right-hemisphere activation compared to left would be observed to infrequent target and novel stimuli. Consistent with predictions, greater right hemisphere than left frontal, temporal, and parietal lobe activity was observed for target detection and novelty processing. Moreover, asymmetry effects did not differ with respect to age or gender of the participants. The results (1) support the proposal that the right hemisphere is differentially engaged in processing salient stimuli and (2) demonstrate the successful use of a new voxel-based laterality analysis technique for fMRI data.

Clinical application of the P300 event-related brain potential

The P300 brain potential can provide information about cognition that is quantitatively comparable to other clinically used biomedical assays. Causes of P300 variability with respect to task and biologic determinants have been well characterized so that refinement of ERP methods for clinical applications is possible. Elaboration of how P300 and other ERP components reflect neuropsychologic processes would help to increase their clinical relevance. In particular, development of reliable P3a paradigms used in conjunction with P3b tasks promises to augment dramatically the applicability and sensitivity of ERPs. Use of P300 as a clinical evaluation tool should be revisited with contemporary theory, methods, and analysis procedures because a reliable neuroelectric measure of mental function would redefine the assessment of cognitive disorders.

Meta-analysis of P300 and schizophrenia: patients, paradigms, and practical implications

The goal of the present meta-analysis was to identify factors that contribute to P300 event-related brain potential (ERP) differences in patients with schizophrenia compared to unaffected controls in an attempt to characterize the clinically relevant dimensions underlying P300 deficits in patients with schizophrenia. P300 effect size (d) was smaller in amplitude and longer in latency in schizophrenic patients compared to normal controls, with the strongest effects obtained from the auditory oddball. Paranoid subtype demonstrated larger P300 amplitude effect sizes than other disease subtypes, and P300 latency effect size decreased with disease duration. Psychopathology severity and antipsychotic medications were unrelated to P300 amplitude effect size. Gender proportion, educational level, and stimulus and task variables also affected P300 amplitude and latency effect sizes. The findings are used to formulate a theoretical account of the empirical data and provide suggestions for maximizing the utility of the P300 component in the assessment of schizophrenia.

[The p300 cognitive event-related potential. II. Individual variability and clinical application in psychopathology]

The P300 wave is one of the cognitive components of the event-related potential (ERP) that is used to investigate the cognitive processes, and which can be used to study patient populations with a variety of psychiatric disorders. Its clinical utility has been increased by the identification of factors that contribute to the variability in its amplitude and latency. However, its value as a diagnostic index has not been entirely established. It can provide a useful recording of patients' information processing, and indicate the severity of the clinical state and its possible evolution. It can also assist in determining what therapeutic approach to adopt. In the present review, the findings in the literature concerning interindividual variation in the P300 wave are first described; several variables significantly influence the amplitude and latency of this wave, such as age, gender, intelligence and personality. Following this, the relevance of the data in the literature on the clinical applications of P300 in psychopathology is examined, including the studies undertaken to obtain an objective diagnostic index for mental disorders and also those carried out to assess the problems concerning the interpretation of information connected with the mental pathologies examined. P300-associated findings on dementia, schizophrenia, depression, alcoholism, drug addiction, anxiety disorders (panic disorder, obsessive-compulsive disorder, and post-traumatic stress syndrome) and on personality disorders (schizoid, antisocial or borderline personality disorder) have been examined in detail.

The auditory event-related potential is a stable and reliable measure in elderly subjects over a 3 year period

OBJECTIVES

Valid markers of psychobiological processes, including changes over the lifespan, must be reliable. This study investigated the reliability of the auditory event-related potential (ERP) over a 3 year period.

METHODS

Predictable and unpredictable rare tones were embedded in common-to-rare sequences at 3 different ratios (2:3, 2:5 and 2:8). Forty-six older (mean age 72.3 years) volunteers pressed a key to the rare tones, and ERPs (Fz, Cz and Pz) and reaction time (RT) were measured. Reliability across years was assessed using 3 methods: (1) determination of the stability of waveform components (P1, N1, P2, N2 and P3); (2) cross-correlation of successive 15 ms epochs of within-subject ERPs; and (3) cross-correlation of 15 ms epochs of between-subject ERPs.

RESULTS

With all analyses, the ERP was stable. Analysis of the scored components indicated that P3 was especially stable in the unpredictable rare (2:8) condition. Earlier components were equally stable across all conditions. Analysis of 15 ms ERP epochs indicated significant ERP stability 60 ms after stimulation, lasting over 640 ms.

CONCLUSIONS

Robust within-subject reliability of the ERP strengthens its potential use for detecting preclinical changes in at-risk elderly populations.

Cognitive event-related potentials in neuropsychological assessment

Neuropsychology is a behavioral approach to studying the brain, and an integration of neuropsychology with on-line processing measures of brain function is important for advancing the understanding of brain-behavior relationships. Cognitive event-related potentials (ERPs) are on-line processing measures that are of interest to neuropsychologists because they are linked to familiar neuropsychological test paradigms and because they have reached a degree of standardization sufficient to make them applicable in individual assessment. A selective review of cognitive ERPs is given, focusing on studies of attention in the oddball paradigm and arguing that an adequate assessment of attention is basic in understanding higher order cognitive functions. General principles for using ERP data to supplement and clarify neuropsychological analysis are discussed, and available evidence on dementia and traumatic head injury is reviewed. It is concluded that ERPs are a useful supplement to neuropsychological assessment. Although diagnostic use of ERPs must be guarded because of limited standardization and validation, information-processing analysis with ERPs may aid significantly in interpretation of behavioral data.

On P300 measurement stability: habituation, intra-trial block variation, and ultradian rhythms

P300 event-related brain potentials (ERPs) were elicited using a simple discrimination task in which participants discriminated two different equiprobable visual stimuli with button-press responses (n = 20). A total of ten trial blocks were presented at 10-min intervals. P300 amplitude declined significantly, but peak latency did not change reliably across trial blocks. P300 amplitude demonstrated a reliable cyclical fluctuation across trial blocks, although P300 latency did not. Intra-trial block ERP variability was assessed by computing the correlation coefficients between the target and standard stimuli for amplitude and latency measures across participants within each trial block. P300 amplitude correlations were weakest at the Fz electrode, more strongly associated at Cz, and were most strongly correlated at Pz across trial blocks. P300 latency correlations were somewhat weaker and similar in strength across electrodes sites. The correlational patterns for both P300 amplitude and latency demonstrated reliable cyclical variation. The N100 component produced strong and consistent correlations for both amplitude and latency, whereas the P200 and N200 component measures evinced cyclical correlational patterns similar to the P300 across trial blocks. These results suggest that the stability of P300 and other component measures can vary appreciably within and across trial blocks in a manner that reflects ultradian variation in arousal level.

Magnetic resonance imaging and P300 (event-related auditory evoked potentials) in the assessment of postoperative cerebral injury following coronary artery bypass graft surgery

Cerebral injury following coronary artery bypass grafting (CABG) surgery was investigated with magnetic resonance imaging (MRI) and P300, a long-latency endogenous evoked potential associated with psychological processing of stimulus information. Twelve patients were studied before and after surgery. Prior to surgery, MRI abnormalities were found in all but one patient. After surgery, five patients had new abnormalities, mainly deep white-matter lesions (DWML). Postoperative P300 latency was significantly increased in six patients. P300 topographical distribution showed a shift from predominantly posterior cerebral regions to frontal regions in most patients. Postoperative P300 and MRI deficits were found in three of the five patients. One of the patients with marked MRI change (DWML in caudate nucleus) did not show P300 deficit.

P300, handedness, and corpus callosal size: gender, modality, and task

The P300 event-related potential (ERP) was elicited in left- and right-handed young adult male and female subjects (n = 20/group), with auditory and visual stimulus modalities from single-stimulus and oddball tasks. P300 amplitude was larger across all conditions for left- compared to right-handed subjects at anterior and central electrode sites. P300 latency was shorter across all conditions for left- compared to right-handers. Task type did not affect the ERP handedness differences. Male and female subjects demonstrated comparable ERP handedness effects, although smaller P300 components were obtained for males compared to females. When considered in the context of previously reported corpus callosal size differences for left- vs. right-handed and male vs. female participants, the findings suggest that the P300 reflects callosal size and inter-hemispheric transmission efficacy.

P300 clinical utility and control of variability

The P300 event-related brain potential (ERP) has been used to study normal aging as well as patient populations with a variety of neurologic and psychiatric disorders. The P300 has demonstrated reasonable success as a means to assess disturbances in cognitive function, and its clinical utility has been enhanced by the identification of factors that contribute to the variability of ERP measurements. In this article, the neuropsychological theory of P300 is reviewed, ways in which this brain potential can be used as a measure of cognitive efficiency are defined, and methodologic issues that must be considered for successful clinical ERP applications are outlined. This approach is then extended to specific recommendations concerning the technical and practical aspects of P300 recording, so that a well-defined normative database can be developed for evaluating individual patients. When appropriate procedures are used, the P300 can provide a highly useful means to quantify human cognitive capability.

Handedness and P300 from auditory stimuli

The P3(00) event-related potential (ERP) was elicited in 20 left- and 20 right-handed normal young adult male subjects using a simple auditory stimulus discrimination task. P3 amplitude from the target stimuli was larger at anterior electrode sites for left- compared to right-handed subjects. P3 latency from the standard stimuli was shorter for left- compared to right-handers. The N1, P2, and N2 components generally demonstrated similar handedness effects. The relationship of ERP amplitude and handedness to anatomical variables and cognitive factors is discussed.

Estimate of physiological variability of peak latency in single sweep P300

Among single sweep records of event-related potentials (ERPs), the peak latency of P300, which is one of the most prominent positive peaks in the ERP obtained in the oddball paradigm, may vary depending on the conditions of the subject. In the analysis of characteristics of the variability in the peak latency, it is important to know to what extent the variability of the measured peak latency (measured variability) is actually caused by physiological factors (physiological variability). In our previous study, a method was developed for judging whether the physiological variability really exists or not, and if it does exist, the developed method extracts the physiological variability from the measured variability based on a limited number of single sweep records. In the present study, based on the P300 waveforms which were detected by blinded visual inspection of the ERP data obtained by an auditory oddball paradigm from 12 healthy adults, the physiological variability was shown to exist with a confidence level of 95% for all subjects. Furthermore, its interval estimate was calculated by subtracting noise variability from the measured variability with a confidence level of 80%, and it was found to range from 17 to 57 ms for all subjects.

Meta-analysis of P300 normative aging studies

The theoretical and empirical backgrounds for the utility of the P300 event-related potential (ERP) as a measure of cognitive aging are summarized. P300 latency data from 32 different normative aging studies are then reviewed and assessed with meta-analytic procedures. Evaluation of moderator variables indicates that sample characteristics, stimulus factors, and task conditions contribute significantly to the "normal" change in peak latency that occurs with aging. These findings are critiqued in the context of previous reports, and implications are outlined for future applications of ERPs to normative aging. It is concluded that P300 latency can provide useful information about cognitive aging but that specific variables must be considered to obtain more precise results.

Hemispheric differences for P300 amplitude from an auditory oddball task

The P3(00) event-related potential (ERP) was elicited in 80 normal, right-handed male subjects using a simple auditory stimulus discrimination task, with electroencephalographic (EEG) activity recorded at 19 electrodes. P300 amplitude was larger over the right compared to left hemisphere electrode sites primarily at anterior-medial locations (F3/4, C3/4) for both target and standard stimuli. The N100, P200, and N200 components also demonstrated several similar, albeit less robust, hemispheric asymmetries. No hemispheric effects for P300 latency were observed, with few consistent latency findings for any of the other components obtained. The results suggest that the discrimination process underlying P300 generation may originate with right frontal activation.

Variability and replicability of the mismatch negativity

The interindividual variation and test-retest stability of the mismatch negativity (MMN) and N1 components of the event-related potential (ERP) were investigated by presenting standard (85%) and deviant tones (15%) to 10 young subjects in 2 sessions separated by 1 month. Deviant tones in different blocks were either frequency or duration changes with interstimulus intervals (ISIs) of 0.5 and 1.5 sec. The results showed a fairly good test-retest stability of the MMN amplitude for both types of changes with each ISI at the group level. The amplitude of the duration MMN showed significant individual test-retest stability. The N1 amplitude showed high stability at both the group and individual levels. Both the MMN and N1 showed considerable interindividual variation. The results suggest that MMN and N1 can be used in follow-up studies not only at the group level but possibly at the individual level also.

Cognitive and biological determinants of P300: an integrative review

The P300 event-related brain potential (ERP) is thought to reflect neuroelectric activity related to cognitive processes such as attention allocation and activation of immediate memory. However, recent studies have provided evidence that the P300 also is influenced by biological processes such as fluctuations in the arousal state of subjects. The effects of natural (circadian, ultradian, seasonal, menstrual) and environmentally induced (exercise, fatigue, drugs) state variables on the P300 are reviewed. The findings suggest that these factors contribute to P300 measures and are discussed in terms of their theoretical and applied implications.

P300 hemispheric amplitude asymmetries from a visual oddball task

The P3(00) event-related potential (ERP) was elicited in 80 normal, right-handed male subjects using a simple visual discrimination task, with electroencephalographic (EEG) activity recorded at 19 electrodes. P3 amplitude was larger over the right than over the left hemisphere electrode sites primarily at anteromedial locations (F3/4, C3/4) for target, novel, and standard stimuli. The N1, P2, and N2 components also demonstrated hemispheric asymmetries. The strongest P3 hemispheric asymmetries for all stimuli were observed at anterior locations, suggesting a frontal right hemisphere localization for initial stimulus processing, although target stimuli produced larger P3 amplitudes at parietal locations that did novel stimuli. The relationships of hemispheric asymmetries to anatomical variables, background EEG activity, and neurocognitive factors are discussed.

Lateralization of event-related potentials during discontinuation of antiepileptic medication

The effect of short-term withdrawal of antiepileptic drugs (AEDs) on auditory event-related potentials (ERPs) was studied in 16 patients undergoing preoperative evaluation for epilepsy surgery. ERPs were performed for all patients during treatment with full medication and after a 1-week period during ongoing tapering of AEDs. To clarify whether AED discontinuation would provide evidence of lateralizing for ERPs, we also studied the subgroup of 9 patients who had already undergone temporal lobectomies (TLE group). In the TLE group, if habitual seizures occurred < 30 h before the ERP recording session, auditory N1 and P3 amplitudes across sphenoidal electrodes were markedly decreased on the side ipsilateral to the epileptic focus. If seizures did not occur, asymmetries in amplitudes were equivocal and not of lateralizing value. In the whole group, midline N1 latencies for standard responses decreased significantly during AED discontinuation. At baseline, long-term habituation of the N1 component for standard responses was attenuated as compared with that of controls. During AED discontinuation, however, enhanced habituation of N1 was observed in TLE patients who did not exhibit seizures before ERP recording.

P300 from an auditory oddball task: inter-laboratory consistency

Event-related potentials (ERPs) were recorded from normal subjects for the purpose of evaluating measurement consistency among six laboratories located in different cities within the United States. At each laboratory location 15 male subjects were tested using a simple auditory stimulus discrimination task and identical electrophysiological equipment and recording methods. Assessment of the N1, P2, N2, and P3(00) potentials from both the target and standard stimuli resulted in no reliable differences among laboratories for component amplitudes, latencies, and scalp distributions. Quantitative evaluation of overall waveform and specific component morphology yielded good to excellent agreement across laboratories. The findings suggest that large-scale inter-laboratory human electrophysiological studies are feasible and may prove of value when using ERPs to evaluate cognitive function in humans.

Focal abnormalities of P3 ERPs unveiled in patients with cortical lesions and primary progressive aphasia by average reference recordings

Event related potentials (ERPs) to an auditory odd-ball paradigm were recorded with the linked earlobe reference (LER) and with a computer calculated average reference (AR), excluding the two linked earlobe derivations. The study was performed in 30 patients with lesions of frontal, parietal, occipital cortex, unilateral and bilateral lesions of the medial temporal lobe (MTL), in four patients affected by Primary Progressive Aphasia (PPA) and in 56 age matched controls. Latencies, amplitudes and scalp distribution of the earlier ERP components (P1, N1, P2, N2) were within normal limits for both LER and AR recordings. P3 scalp distribution in patients was normal when LER was used, with the exception of two patients affected by bilateral MTL lesions. When P3 was recorded using AR, the scalp distribution was statistically different from normal distributions in all patients. A negativity, instead of the positive P3 observed in controls, was recorded in patients from leads corresponding to the affected areas. This finding might have clinical applications, and confirms earlier studies suggesting that P3 is generated simultaneously from different cortical areas.

Long-term test-retest reliability of event-related potentials in normals and alcoholics

The long-term test-retest reliability of event-related potentials (ERP) measures was examined in a group of 44 controls and 71 chronic alcoholics, retested after an average of 14 months. Correlational analyses revealed moderately significant test-retest correlations for visual and auditory target N1, N2, and P3 amplitudes, with significant correlations for N1, N2 and P3 latencies. Controls and alcoholics produced similar test-retest correlations for visual and auditory ERP measures. Men and women produced equally stable ERP measures over time. Overall N1 and P3 amplitudes were most reliable in both groups followed by N2 amplitude, N1 and N2 latency, and P3 latency. The stability of ERP measures found in this study over a 14-month period in both normals and chronic alcoholics supports the use of ERPs in the study of normal and disordered cognitive functioning.

Evidence for terminal decline in the event-related potential of the brain

Precipitous decline (terminal decline) characterizes changes in the elderly just prior to death. The neurological and temporal parameters of terminal decline are not defined. The present study compared sensitive changes in the brain event-related potential (ERP) in 7 subjects who died within 1 year of evaluation with matched controls. Cross-correlation of annual ERPs revealed disorganization within and between subjects in response to memory dependent conditions but not in response to a novel stimulus (oddball). Motor reaction time to targets was not sensitive to decline. The changes associated with impending death were restricted to decline in reliability of the ERP within 1 year of death.

Age-related features of the resting and P300 auditory evoked responses using the dipole localization method and cortical imaging technique

Two mathematical techniques, the dipole localization method (DLM) and the cortical imaging technique (CIT), are used to analyze the resting and P300 auditory responses in young and old normal volunteers. These methods identify certain age-related features of these evoked responses that are not found by standard topographic methods. These features include the orientation of the P200 resting response, and the laterality of the N120 response, and the eccentricity of the P300 response in the P300 stimulus condition. Theoretical dipole sources and simulated cortical surface maps are also constructed for one normal subject and one psychiatric inpatient and compared. These mathematical methods appear to enhance the discriminating power of traditional electrophysiological measures.

Acute, withdrawal, and chronic alcohol effects in man: event-related potential and quantitative EEG techniques

The results presented here strongly suggest that quantitative electroencephalography and event-related potentials are excellent research tools and may be clinically useful as non-invasive monitors of psychotropic drug action and encephalopathies. Our initial data with acute mild alcohol intoxication show that acute tolerance may be reflected in qEEG but not in P3 latency. Since predictably some brain functions may show tolerance, and others not, these approaches may be useful probes. The amplitude of N1-P2 appears to differentiate alcoholics with and without a history of withdrawal seizures. This technique may thus prove useful in determining treatment and monitoring treatment effects in alcohol withdrawal. P3 latency appears to be normal in Korsakoff's syndrome, unlike in Alzheimer's disease. The combination of the event-related potentials with neuropsychology and magnetic resonance imaging scans should be invaluable for future research in these patient groups. Many patients with severe liver disease superficially appear mentally intact. The event-related potential and quantitative electroencephalography findings we have demonstrated may indicate those at greater risk for alterations in brain functioning. These techniques may also prove useful in diagnosing other "subclinical" encephalopathies and further our understanding of the underlying brain pathophysiology.

Mapping of event-related potentials to auditory and visual odd-ball paradigms

This paper reports the results of recordings and maps of event-related potentials (ERPs) obtained in normal subjects, patients with Alzheimer's disease (AD), progressive supranuclear palsy, confusional states, and in subjects with homonymous hemianopsia. ERPs were recorded from 19 scalp electrode derivations using both visual and acoustic paradigms. In normal subjects, the topographical distribution of all ERP components is described in detail. In 45% of AD patients, ERPs were normal; in 35%, although present, ERP components were delayed, while in the other 20% the N2 and P3 peaks could not be recorded. In patients with progressive supranuclear palsy, the normal ERP sequence was not identified. Our findings in normals and in hemianopic patients suggest that the early modulation of stimulus-related potentials could be located in primary associative areas, and that N2, P3a, P3b, SW should have different origins.