P300 hemispheric amplitude asymmetries from a visual oddball task

Frontal P300 asymmetry and congruence judgment: Retroactive switching is impaired during school day mornings in female adolescents

Investigating frontal EEG asymmetry as a possible biomarker of cognitive control abilities is especially important in ecological contexts such as school and work. We used a novel approach combining judgment performance and hemispheric frontal event-related potential (ERP) P300 asymmetry (fP3As) to evaluate aspects of cognitive control (i.e., repetition and switching) in adolescent females over a two-week ordinary school period. While undergoing electroencephalographic recording, students performed a word-colour "Stroop-like" congruence judgment task during morning and afternoon sessions, on Mondays and Wednesdays. Proportion of incongruence and congruence trials was 75% and 25%, respectively. ERP analysis revealed larger "novelty" right hemispheric fP3As amplitude for infrequent congruence but equivalent or significantly smaller than left hemispheric fP3As amplitude for frequent incongruence. RTs increased with extent of right fP3As shift. Behaviorally, repeat trial pairs (i.e., congruent followed by congruent, incongruent followed by incongruent) generally did not differ by time or day and were associated with near-ceiling accuracy. In contrast, switch trial pairs (i.e., congruent followed by incongruent, incongruent followed by congruent) in the afternoon were slower and associated with lower accuracy at the expected 75% criterion rate (i.e., judging incongruence by default), dropping significantly below 75% in the mornings. Crucially, compared to afternoon, morning fP3As patterns did not change adaptively with switch trial pairs. Although retroactive switching during congruence judgment was affected at all testing times, we conclude it was most impaired in the mornings of both early and mid school weeks, supporting misalignment between adolescent circadian cycle and school start time. We discuss some implications for optimal learning of adolescents at school.

P3a amplitude to trauma-related stimuli reduced after successful trauma-focused PTSD treatment

An elevated P3a amplitude to trauma-related stimuli is strongly associated with posttraumatic stress disorder (PTSD), yet little is known about whether this response to trauma-related stimuli is affected by treatment that decreases PTSD symptoms. As an analysis of secondary outcome measures from a randomized controlled trial, we investigated the latency and amplitude changes of the P3a in responses in a three-condition oddball visual task that included trauma-related (combat scenes) and trauma-unrelated (threatening animals) distractors. Fifty-five U.S. veterans diagnosed with combat-related PTSD were randomized to receive either active or sham repetitive transcranial magnetic stimulation (rTMS). All received cognitive processing therapy, CPT+A, which requires a written account of the index trauma. They were tested before and 6 months after protocol completion. P3a amplitude and response time decreases were driven largely by the changes in the responses to the trauma-related stimuli, and this decrease correlated to the decrease in PTSD symptoms. The amplitude changes were greater in those who received rTMS + CPT than in those who received sham rTMS + CPT, suggesting that rTMS plays beneficial role in reducing arousal and threat bias, which may allow for more effective engagement in trauma-focused PTSD treatment.

Neurophysiological responses of globus pallidus internus during the auditory oddball task in Parkinson's disease

Parkinson's disease can be associated with significant cognitive impairment that may lead to dementia. Deep brain stimulation (DBS) of the subthalamic nucleus is an effective therapy for motor symptoms but is associated with cognitive decline. DBS of globus pallidus internus (GPi) poses less risk of cognitive decline so may be the preferred target. A research priority is to identify biomarkers of cognitive decline in this population, but efforts are hampered by a lack of understanding of the role of the different basal ganglia nuclei, such as the globus pallidus, in cognitive processing. During deep brain stimulation (DBS) surgery, we monitored single units, beta oscillatory LFP activity as well as event related potentials (ERPs) from the globus pallidus internus (GPi) of 16 Parkinson's disease patients, while they performed an auditory attention task. We used an auditory oddball task, during which one standard tone is presented at regular intervals and a second deviant tone is presented with a low probability that the subject is requested to count and report at the end of the task. All forms of neuronal activity studied were selective modulated by the attended tones. Of 62 neurons studied, the majority (51 or 82%) responded selectively to the deviant tone. Beta oscillatory activity showed an overall desynchronization during both types of attended tones interspersed by bursts of beta activity giving rise to peaks at a latency of around 200 ms after tone onset. cognitive ERPs recorded in GPi were selective to the attended tone and the right-side cERP was larger than the left side. The averages of trials showing a difference in beta oscillatory activity between deviant and standard also had a significant difference in cERP amplitude. In one block of trials, the random occurrence of 3 deviant tones in short succession silenced the activity of the GPi neuron being recorded. Trial blocks where a clear difference in LFP beta was seen were twice as likely to yield a correct tone count (25 vs 11). The data demonstrate strong modulation of GPi neuronal activity during the auditory oddball task. Overall, this study demonstrates an involvement of GPi in processing of non-motor cognitive tasks such as working memory and attention, and suggests that direct effects of DBS in non-motor GPi may contribute to cognitive changes observed post-operatively.

Oddball onset timing: Little evidence of early gating of oddball stimuli from tapping, reacting, and producing

Oddballs, rare or novel stimuli, appear to last longer than non-oddballs. This illusion is often attributed to the perceived time that an oddball occupies being longer than that of a non-oddball. However, it is also possible that oddball stimuli are perceived to onset earlier than non-oddballs; they are “gated” earlier in time and thus the perceived duration of those stimuli are longer. In the current article, we directly investigate this proposal by asking participants to react to, produce durations initiated with, and tap along to either oddball or standard stimuli. Tapping provided some support for earlier perceived onset of an oddball in the visual modality. However, both reaction time and duration production experiments provided evidence against an oddball being gated earlier than a standard stimulus. Contrarily, these experiments showed an oddball resulted in longer reaction times and productions, respectively. Taken together, these three experiments indicate it is unlikely that the expansion of time attributed to oddball presentation is purely due to the earlier gating of oddball stimuli. In fact, the first two experiments provide some evidence that the effect of an oddball must compensate for the later gating of these stimuli.

Olfactory Influences on Visual Categorization: Behavioral and ERP Evidence

Visual stimuli often dominate nonvisual stimuli during multisensory perception. Evidence suggests higher cognitive processes prioritize visual over nonvisual stimuli during divided attention. Visual stimuli should thus be disproportionally distracting when processing incongruent cross-sensory stimulus pairs. We tested this assumption by comparing visual processing with olfaction, a “primitive” sensory channel that detects potentially hazardous chemicals by alerting attention. Behavioral and event-related brain potentials (ERPs) were assessed in a bimodal object categorization task with congruent or incongruent odor–picture pairings and a delayed auditory target that indicated whether olfactory or visual cues should be categorized. For congruent pairings, accuracy was higher for visual compared to olfactory decisions. However, for incongruent pairings, reaction times (RTs) were faster for olfactory decisions. Behavioral results suggested that incongruent odors interfered more with visual decisions, thereby providing evidence for an “olfactory dominance” effect. Categorization of incongruent pairings engendered a late “slow wave” ERP effect. Importantly, this effect had a later amplitude peak and longer latency during visual decisions, likely reflecting additional categorization effort for visual stimuli in the presence of incongruent odors. In sum, contrary to what might be inferred from theories of “visual dominance,” incongruent odors may in fact uniquely attract mental processing resources during perceptual incongruence.

Sparse EEG Source Localization Using LAPPS: Least Absolute l-P (0 < p < 1) Penalized Solution

OBJECTIVE

The electroencephalographic (EEG) inverse problem is ill-posed owing to the electromagnetism Helmholtz theorem and since there are fewer observations than the unknown variables. Apart from the strong background activities (ongoing EEG), evoked EEG is also inevitably contaminated by strong outliers caused by head movements or ocular movements during recordings.

METHODS

Considering the sparse activations during high cognitive processing, we propose a novel robust EEG source imaging algorithm, LAPPS (Least Absolute -P (0 < p < 1) Penalized Solution), which employs the -loss for the residual error to alleviate the effect of outliers and another -penalty norm (p=0.5) to obtain sparse sources while suppressing Gaussian noise in EEG recordings. The resulting optimization problem is solved using a modified ADMM algorithm.

RESULTS

Simulation study was performed to recover sparse signals of randomly selected sources using LAPPS and various methods commonly used for EEG source imaging including WMNE, -norm, sLORETA and FOCUSS solution. The simulation comparison quantitatively demonstrates that LAPPS obtained the best performances in all the conducted simulations for various dipoles configurations under various SNRs on a realistic head model. Moreover, in the localization of brain neural generators in a real visual oddball experiment, LAPPS obtained sparse activations consistent with previous findings revealed by EEG and fMRI.

CONCLUSION

This study demonstrates a potentially useful sparse method for EEG source imaging, creating a platform for investigating the brain neural generators.

SIGNIFICANCE

This method alleviates the effect of noise and recovers sparse sources while maintaining a low computational complexity due to the cheap matrix-vector multiplication.

Brain-Machine Interfaces: From Basic Science to Neuroprostheses and Neurorehabilitation

Brain-machine interfaces (BMIs) combine methods, approaches, and concepts derived from neurophysiology, computer science, and engineering in an effort to establish real-time bidirectional links between living brains and artificial actuators. Although theoretical propositions and some proof of concept experiments on directly linking the brains with machines date back to the early 1960s, BMI research only took off in earnest at the end of the 1990s, when this approach became intimately linked to new neurophysiological methods for sampling large-scale brain activity. The classic goals of BMIs are 1) to unveil and utilize principles of operation and plastic properties of the distributed and dynamic circuits of the brain and 2) to create new therapies to restore mobility and sensations to severely disabled patients. Over the past decade, a wide range of BMI applications have emerged, which considerably expanded these original goals. BMI studies have shown neural control over the movements of robotic and virtual actuators that enact both upper and lower limb functions. Furthermore, BMIs have also incorporated ways to deliver sensory feedback, generated from external actuators, back to the brain. BMI research has been at the forefront of many neurophysiological discoveries, including the demonstration that, through continuous use, artificial tools can be assimilated by the primate brain's body schema. Work on BMIs has also led to the introduction of novel neurorehabilitation strategies. As a result of these efforts, long-term continuous BMI use has been recently implicated with the induction of partial neurological recovery in spinal cord injury patients.

Why won't they sit with me? An exploratory investigation of stereotyped cues, social exclusion, and the P3b

The importance of understanding how we anticipate and prepare for being socially excluded is underscored by the numerous adverse mental and physical consequences of social rejection. In this study, we adapted a social exclusion paradigm, the Lunchroom task, to investigate the use of social context cues in the formation of social outcome expectations as indexed by the P3b, an ERP component associated with attention orientation and context updating. In this task, Black and White participants were presented with either neutral or stereotyped cues prior to being exposed to simulated inclusion versus exclusion outcome scenarios. Black participants showed evidence of (1) a significantly reduced P3b response to exclusions preceded by stereotyped cues relative to neutral cue-related exclusions and (2) a marginally significant increase in the P3b response to inclusions relative to exclusions when both were preceded by stereotyped cues. Both of these findings suggest a key role for the use of social cues in the formation of outcome expectations. In line with our hypothesis that the random intermixing of inclusion and exclusion outcomes would prevent formation of outcome expectations when coupled with the absence of self-relevant cues, no overall P3b modulations were observed among a comparison group of White participants.

Attitudes to the Right: Evaluative Processing is Associated with Lateralized Late Positive Event-Related Brain Potentials

The authors recently developed a paradigm to investigate the evaluative categorization stage of attitudes using event-related brain potentials (ERPs). The present series of studies extended this approach by analyzing the spatial topography of the ERP over the lateral scalp region to address complementary questions regarding the nature of operations underlying the evaluative categorization stage of attitude processing. Consistent with the hypothesis that evaluative categorizations engage mechanisms associated with hedonic or global language processing, results revealed that the standardized amplitudes of the late positive potential of the ERP during evaluative categorizations were larger over the right than the left scalp region, whereas nonevaluative categorizations were associated with a symmetrically distributed ERP across the left and right scalp regions.

Executive Cognitive Functioning and Risk for Substance Abuse

Individuals with a substance use disorder (SUD) exhibit deficits in executive cognitive functioning (ECF). ECF is involved in the regulation of goal-directed behavior and includes abilities such as attentional control, strategic goal planning, organization, and cognitive flexibility. The prefrontal cortex is believed to be the primary cortical substrate that subserves ECF. Children deemed at high risk for drug abuse because they have parents with SUD similarly demonstrate cognitive limitations suggesting an ECF deficit. High-risk children, as a group, also exhibit deviations in temperament, an attenuated amplitude of the P300 event-related potential, and heightened aggressivity compared with control groups. These latter characteristics are associated with low ECF capacity and are believed to reflect dysfunction within the prefrontal cortex. It is hypothesized that deviations on these traits form a core disorder of affective, cognitive, and behavioral dysregulation that serves as a general vulnerability factor for SUD.

A different view on the checkerboard? Alterations in early and late visually evoked EEG potentials in Asperger observers

BACKGROUND

Asperger Autism is a lifelong psychiatric condition with highly circumscribed interests and routines, problems in social cognition, verbal and nonverbal communication, and also perceptual abnormalities with sensory hypersensitivity. To objectify both lower-level visual and cognitive alterations we looked for differences in visual event-related potentials (EEG) between Asperger observers and matched controls while they observed simple checkerboard stimuli.

METHODS

In a balanced oddball paradigm checkerboards of two checksizes (0.6° and 1.2°) were presented with different frequencies. Participants counted the occurrence times of the rare fine or rare coarse checkerboards in different experimental conditions. We focused on early visual ERP differences as a function of checkerboard size and the classical P3b ERP component as an indicator of cognitive processing.

RESULTS

We found an early (100-200 ms after stimulus onset) occipital ERP effect of checkerboard size (dominant spatial frequency). This effect was weaker in the Asperger than in the control observers. Further a typical parietal/central oddball-P3b occurred at 500 ms with the rare checkerboards. The P3b showed a right-hemispheric lateralization, which was more prominent in Asperger than in control observers.

DISCUSSION

The difference in the early occipital ERP effect between the two groups may be a physiological marker of differences in the processing of small visual details in Asperger observers compared to normal controls. The stronger lateralization of the P3b in Asperger observers may indicate a stronger involvement of the right-hemispheric network of bottom-up attention. The lateralization of the P3b signal might be a compensatory consequence of the compromised early checksize effect. Higher-level analytical information processing units may need to compensate for difficulties in low-level signal analysis.

Capturing dynamic patterns of task-based functional connectivity with EEG

A new approach to trace the dynamic patterns of task-based functional connectivity, by combining signal segmentation, dynamic time warping (DTW), and Quality Threshold (QT) clustering techniques, is presented. Electroencephalography (EEG) signals of 5 healthy subjects were recorded as they performed an auditory oddball and a visual modified oddball tasks. To capture the dynamic patterns of functional connectivity during the execution of each task, EEG signals are segmented into durations that correspond to the temporal windows of previously well-studied event-related potentials (ERPs). For each temporal window, DTW is employed to measure the functional similarities among channels. Unlike commonly used temporal similarity measures, such as cross correlation, DTW compares time series by taking into consideration that their alignment properties may vary in time. QT clustering analysis is then used to automatically identify the functionally connected regions in each temporal window. For each task, the proposed approach was able to establish a unique sequence of dynamic pattern (observed in all 5 subjects) for brain functional connectivity.

Auditory novelty processing is enhanced in obsessive-compulsive disorder

BACKGROUND

Cognitive models propose that anxiety disorders are associated with an attentional bias toward potentially threatening stimuli. In this study, it was analyzed whether patients with obsessive-compulsive disorder (OCD) show enhanced responses of their event-related brain potentials to novel stimuli, either in a context of potential threat or in a neutral context.

METHODS

In this study, 20 OCD patients and 20 matched healthy control subjects performed a visual recognition task during which irrelevant repeated standard sounds and unitary novel sounds were interspersed.

RESULTS

As expected, OCD patients showed an increase in the novelty-P3 amplitude elicited by unitary novel sounds. However, no effect of emotional context conditions was observed.

CONCLUSION

It is suggested that the novelty P3 amplitude increase in OCD patients represents a physiological indicator of an enhanced cortical orienting response implicating stronger involuntary shifts of attention. This characteristic is driven by novelty per se and not moderated by potential threat of upcoming events.

The less BOLD, the wiser: support for the latent resource hypothesis after traumatic brain injury

Previous studies of the BOLD response in the injured brain have revealed neural recruitment relative to controls during working memory tasks in several brain regions, most consistently the right prefrontal cortex and anterior cingulate cortices. We previously proposed that the recruitment observed in this literature represents auxiliary support resources, and that recruitment of PFC is not abnormal or injury specific and should reduce as novelty and challenge decrease. The current study directly tests this hypothesis in the context of practice of a working memory task. It was hypothesized that individuals with brain injury would demonstrate recruitment of previously indicated regions, behavioral improvement following task practice, and a reduction in the BOLD signal in recruited regions after practice. Individuals with traumatic brain injury and healthy controls performed the n-back during fMRI acquisition, practiced each task out of the scanner, and returned to the scanner for additional fMRI n-back acquisition. Statistical parametric maps demonstrated a number of regions of recruitment in the 1-back in individuals with brain injury and a number of corresponding regions of reduced activation in individuals with brain injury following practice in both the 1-back and 2-back. Regions of interest demonstrated reduced activation following practice, including the anterior cingulate and right prefrontal cortices. Individuals with brain injury demonstrated modest behavioral improvements following practice. These findings suggest that neural recruitment in brain injury does not represent reorganization but a natural extension of latent mechanisms that engage transiently and are contingent upon cerebral challenge.

Novelty enhancements in memory are dependent on lateral prefrontal cortex

Physiological evidence indicates that several brain regions, including the medial temporal lobes and prefrontal cortex (PFC), are involved in processing events that are novel or distinctive in their immediate context. However, behavioral studies that investigate whether these regions are critical for producing stimulus novelty advantages in memory are limited. For example, evidence from an animal lesion study indicated that the PFC is involved in stimulus novelty effects, but this has not been examined in humans. In the current study, we used a von Restorff novelty paradigm to test a large cohort of lateral PFC patients (n = 16). We found that patients with lateral PFC damage were impaired in recollection- and familiarity-based recognition, and they did not exhibit a normal memory advantage for novel compared with non-novel items. These results provide neuropsychological evidence supporting a key role for the lateral PFC in producing stimulus novelty advantages in memory.

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.

Event Related Potentials (Erp) and Behavioral Measurements to Verbal Stimulation of Visual Fields

Event related potentials (ERP) to visually presented linguistic stimuli were examined using a lexical-decision task and an oddball paradigm. Stimuli were presented to the central, right or left visual fields (CVF, RVF and LVF) and generated ERP with very clear N100-P300 components. The question addressed was whether there is ERP evidence for left hemisphere (LH) superiority in linguistic discrimination as reported behaviorally. Nineteen young, right-handed male subjects participated. The main factor influencing the latency and amplitude of N100 was that of contralateral versus ipsilateral stimulation. Shorter N100 latency and larger amplitude were recorded over the hemisphere contralateral to the visual field stimulated. In contrast, the factors influencing the P300 parameters were the visual field stimulated and the hemisphere over which the ERP was recorded. P300 amplitude was significantly larger and P300 latency significantly shorter over the LH than over the RH. Significantly shorter P300 latency and larger peak amplitude were found for RVF than for LVF stimulation.

Normative Variation of P3a and P3b from a Large Sample

Abstract. The P3a and P3b components were elicited in 120 (60 females, 60 males) young adults using a visual three-stimulus event-related brain potential (ERP) oddball paradigm in which subjects responded to an infrequent target. The major purpose of the paper was to provide a statistically strong characterization of these related P300 subcomponents. P3a components were obtained from the infrequently presented distracter stimulus, which was a large blue square. P3b components were obtained from the target stimulus, which was a blue circle that differed slightly in diameter from the standard stimulus blue circle. Amplitude measures demonstrated that P3a was maximum at Cz, and P3b was maximum at Pz; latency measures increased for both potentials from frontal to parietal recording sites. P3a and P3b from females were larger and later than those from male subjects, with topographic and appreciable individual difference variability observed. P3a was generally unrelated to response time. P3b amplitude was negatively correlated over right frontal areas with P3b latency and positively correlated over right parietal areas to response time. Theoretical implications are discussed.

Time course of processes underlying picture and word evaluation: an event-related potential approach

A substantial body of research suggests that the cognitive mechanisms for picture and word processes are functionally and anatomically distinct. In spite of significant advancements in the understanding of pictures and words, the electrophysiological activities mediating these processes are not well known. To address this issue, we examined event-related brain potentials (ERPs) to pictures and their printed names in a modified dual-target oddball task. ERPs were recorded while participants classified schematic pictures and their corresponding names into target and nontarget categories. Results showed that pictures and words were associated with electrophysiological responses that differed temporally and topographically. In comparison to words, P300s to pictures were characterized by shorter latency and larger amplitude at parietal electrodes. In contrast, words produced greater P200 amplitude at frontal areas. The results are consistent with the view that categorization of pictures is faster than words. Findings are discussed in relation to stimulus evaluation and the time course for picture and word classification.

Neuropsychology and neuropharmacology of P3a and P3b

Perspectives on the P300 event-related brain potential (ERP) are reviewed by outlining the distinction between the P3a and P3b subcomponents. The critical factor for eliciting P3a is how target/standard discrimination difficulty rather than novelty modulates task processing. The neural loci of P3a and P3b generation are sketched and a theoretical model is developed. P3a originates from stimulus-driven disruption of frontal attention engagement during task processing. P3b originates when temporal-parietal mechanisms process the stimulus information for memory storage. The neuropharmacological implications of this view are then outlined by evaluating how acute and chronic use of ethanol, marijuana, and nicotine affect P3a and P3b. The findings suggest that the circuit underlying ERP generation is influenced in a different ways for acute intake and varies between chronic use levels across drugs. Theoretical implications are assessed.

The Influence of Unequal Numbers of Trials on Comparisons of Average Event-Related Potentials

Four studies examined (a) how event-related potentials (ERPs) change as the number of trials averaged increases and (b) the statistical implications of comparing ERPs composed of different numbers of trials. Experiment 1 utilized data from 7-year-old children performing an oddball task. The other three experiments used simulated data with different distributions of P3 peak latency. In all 4 experiments, peak amplitude decreased and the mean amplitude of the 300 to 900 msec interval remained stable as the number of trials averaged increased. The standard deviations of both measures decreased. These data show that the decrease in peak amplitude with increasing numbers of trials that has been found in other studies is not solely due to the elimination of residual noise but is likely to also involve a fundamental aspect of signal averaging and the algorithm used to select peaks. Furthermore, these experiments expose the possibility of statistical errors when investigators compare average ERPs composed of small versus large numbers of trials as is often done when the oddball paradigm is used.

Alcoholism risk, tobacco smoking, and P300 event-related potential

OBJECTIVE

The P300 event-related potential (ERP) is sometimes larger for individuals at low- compared to high-risk for alcoholism. These effects are inconsistent, and how P300 is affected by tobacco smoking in the context of alcoholism risk is unknown. The present study used P300 to examine the inter-relationship between alcoholism heritability and smoking status.

METHODS

P300 was elicited with a visual discrimination task from young adults at low- and high-risk for alcoholism. Half of the subjects in each risk category reported that they did not smoke cigarettes, and the other half reported that they smoked regularly, with equal numbers of male and female subjects assessed. ERPs were recorded, and subjects were instructed to respond only to an infrequently presented target stimulus that occurred in a series of standard and distracter stimuli.

RESULTS

P300 amplitude from the target stimuli was larger for the low-risk compared to high-risk subjects overall. However, smoking status demonstrated even stronger effects, with non-smokers producing consistently larger component amplitudes than smokers and accounting for more variance than alcoholism risk. These group factors also significantly affected P300 scalp topography. No reliable alcoholism risk or smoking group effects were obtained for the ERPs from the other stimuli.

CONCLUSIONS

The findings suggest that P300 measures of alcoholism risk in young adults are moderated by smoking status. Theoretical implications are discussed.

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.

Examining the effects of electromagnetic fields emitted by GSM mobile phones on human event-related potentials and performance during an auditory task

OBJECTIVE

Due to the widespread use of mobile phones (MP), it is important to determine whether they affect human physiology. The aim of this study was to explore the sensitivity of auditory event-related potentials to electromagnetic emissions.

METHODS

Twelve participants attended two sessions, 1 week apart. Participants performed an auditory oddball task while they were exposed to an active MP during one session and sham exposure during the other. Each condition lasted 1 h and order was counterbalanced. N100 and P200 latencies and amplitudes were analysed for non-target waveforms, and N200 and P300 latencies and amplitudes were analysed for target waveforms.

RESULTS

In real relative to sham exposure N100 amplitude and latency to non-targets were reduced, with the reduction larger over midline and right hemisphere sites. P300 latency to targets was delayed in the real exposure condition, however as this difference was greatest at left frontal and left central sites the interpretation of this result is unclear. Reaction time increased in the real relative to sham condition. No difference in accuracy was found.

CONCLUSIONS

The results suggest that MP exposure may affect neural activity, particularly in proximity to the phone, however caution should be applied due to the small sample size.

Gene-environment interplay in alcoholism and other substance abuse disorders: expressions of heritability and factors influencing vulnerability

Factors that confer predisposition and vulnerability for alcoholism and other substance abuse disorders may be described usefully within the gene-environment interplay framework. Thus, it is postulated that heritability provides a major contribution not only to alcohol but also to other substances of abuse. Studies of evoked potential amplitude reduction have provided a highly suitable and testable method for the assessment of both environmentally-determined and heritable characteristics pertaining to substance use and dependence. The different personal attributes that may co-exist with parental influence or exist in a shared, monozygotic relationship contribute to the final expression of addiction. In this connection, it appears that personality disorders are highly prevalent co-morbid conditions among addicted individuals, and, this co-morbidity is likely to be accounted for by multiple complex etiological relationships, not least in adolescent individuals. Co-morbidity associated with deficient executive functioning may be observed too in alcohol-related aggressiveness and crimes of violence. The successful intervention into alcohol dependence and craving brought about by baclofen in both human and animal studies elucidates glutamatergic mechanisms in alcoholism whereas the role of the dopamine transporter, in conjunction with both the noradrenergic and serotonergic transporters, are implicated in cocaine dependence and craving. The role of the cannabinoids in ontogeny through an influence upon the expression of key genes for the development of neurotransmitter systems must be considered. Finally, the particular form of behaviour/characteristic outcome due to childhood circumstance may lie with biological, gene-based determinants, for example individual characteristics of monoamine oxidase (MAO) activity levels, thereby rendering simple predictive measures both redundant and misguiding.

An ERP study of sensory mismatch expressions in Japanese

Combinations of different sensory words produce mismatch expressions like smooth color and red touch in contrast to normal expressions like red color and smooth touch. Concerning these sensory mismatch expressions, results of three experiments are reported. Experiment 1 revealed that (i) mismatch expressions were less comprehensible than normal expressions, and that (ii) there were two patterns among mismatch expressions: the high-comprehensible mismatch expression (HighCME, e.g., smooth color) and the low-comprehensible mismatch expression (LowCME, e.g., red touch). Experiment 2 revealed that the mismatch expressions produced a significantly greater N400 amplitude than the normal expressions. Experiment 3 implied that the difference between High/LowCME was reflected in a later latency band or in a topographical difference of N400, although the statistical significance was marginal. It is argued that the processes to integrate linguistic elements (e.g., combining adjectives and nouns) are not homogeneous.

Event-related potential assessment of information processing after closed head injury

We evaluated alterations in information processing after closed head injury as a function of task demands and stimulus modality. Visual and auditory discrimination tasks were administered to 11 survivors of a head injury and 16 matched healthy controls. In auditory tasks, compared with controls, the survivors had smaller N100s, smaller and later N200s, a more posterior scalp distribution of N200, and longer P300 and response latencies. Auditory N200 and P300 correlated highly with duration of unconsciousness. In contrast, in visual tasks, only a reduced N200 in the survivors differentiated the groups. Our results indicate that processing of auditory stimuli, including the perception and discrimination of stimulus features and the evaluation and categorization of stimuli, may be impaired after head trauma. Visual sensory processing may be spared, but higher-order visual processing involved in stimulus classification may be compromised.

Contributions of the prefrontal cortex to the neural basis of human decision making

The neural basis of decision making has been an elusive concept largely due to the many subprocesses associated with it. Recent efforts involving neuroimaging, neuropsychological studies, and animal work indicate that the prefrontal cortex plays a central role in several of these subprocesses. The frontal lobes are involved in tasks ranging from making binary choices to making multi-attribute decisions that require explicit deliberation and integration of diverse sources of information. In categorizing different aspects of decision making, a division of the prefrontal cortex into three primary regions is proposed. (1) The orbitofrontal and ventromedial areas are most relevant to deciding based on reward values and contribute affective information regarding decision attributes and options. (2) Dorsolateral prefrontal cortex is critical in making decisions that call for the consideration of multiple sources of information, and may recruit separable areas when making well defined versus poorly defined decisions. (3) The anterior and ventral cingulate cortex appear especially relevant in sorting among conflicting options, as well as signaling outcome-relevant information. This topic is broadly relevant to cognitive neuroscience as a discipline, as it generally comprises several aspects of cognition and may involve numerous brain regions depending on the situation. The review concludes with a summary of how these regions may interact in deciding and possible future research directions for the field.

Age-related changes in fronto-parietal networks during spatial memory: an ERP study

Spatial attention and memory were compared in young and old subjects using non-delayed and delayed matching-to-sample tests. Both young and older subjects revealed a right hemisphere superiority for spatial processing. Older subjects were as accurate as young controls in the non-delay task supporting preserved attention ability in this spatial task. However, older subjects were impaired at 3 s retention intervals supporting an encoding and/or retrieval deficit in spatial memory. Stimulus evaluation demands were highest in the non-delay task and younger subjects generated the largest posterior P3 in this condition plus an additional frontal P3. The frontal P3 was reduced in amplitude in the delay tasks in the young subjects. Retention of spatial information during the delay period was characterized by a negative slow wave maximal over Pz that predicted later memory performance and was enhanced in those subjects with high memory performance. Conversely, older subjects generated a frontal P3 in both delay and non-delay conditions and a reduced sustained posterior scalp negativity in some delay conditions. The results support age-related alterations in frontal-parietal networks during spatial memory.

P300 asymmetry in schizophrenia: a meta-analysis

P300 event-related brain potential (ERP) amplitude is smaller in patients with schizophrenia compared to unaffected controls, but whether left temporal component amplitude is also smaller is debated. The present study employed meta-analytical methods to quantitatively assess previous P300 schizophrenia asymmetry findings. All P300 articles on schizophrenia using an auditory oddball paradigm published before January 2000 were obtained by comprehensive literature searches and cross-referencing for related articles. A total of 19 original articles reporting complete midline electrode data and 11 articles reporting lateral asymmetry electrode data were reviewed, which included different independent conditions that yielded 50 independent data sets. P300 amplitude differences between patients with schizophrenia and control subjects from the midline electrodes yielded effect sizes that differed among recording sites, such that Fz was significantly smaller than Pz, with Cz effect sizes smaller than Pz but larger than Fz. Comparison of P300 amplitude from the lateral data for the T3 and T4 electrodes found no reliable effect size difference when these electrodes were analyzed separately. However, comparison of P300 amplitude effect sizes from the TCP1 was significantly larger than that from the TCP2 when these electrodes were analyzed separately. P300 amplitude is smaller overall in patients with schizophrenia compared to control subjects and differs in its effect size topography across the midline and temporal electrode sites, with the strongest effect sizes obtained for the Pz midline and TCP1 lateral electrodes.

An Event-Related fMRI Study of Visual and Auditory Oddball Tasks

Abstract Whole brain event-related functional magnetic resonance imaging (fMRI) techniques were employed to elucidate the cerebral sites involved in processing rare target and novel visual stimuli during an oddball discrimination task. The analyses of the hemodynamic response to the visual target stimuli revealed a distributed network of neural sources in anterior and posterior cingulate, inferior and middle frontal gyrus, bilateral parietal lobules, anterior superior temporal gyrus, amygdala, and thalamus. The analyses of the hemodynamic response for the visual novel stimuli revealed an extensive network of neural activations in occipital lobes and posterior temporal lobes, bilateral parietal lobules, and lateral frontal cortex. The hemodynamic response associated with processing target and novel stimuli in the visual modality were also compared with data from an analogous study in the auditory modality ( Kiehl et al., 2001 ). Similar patterns of activation were observed for target and novel stimuli in both modalities, but there were some significant differences. The results support the hypothesis that target detection and novelty processing are associated with neural activation in widespread neural areas, suggesting that the brain seems to adopt a strategy of activating many potentially useful brain regions despite the low probability that these brain regions are necessary for task performance.

Visual P300 and the self-directedness scale of the Temperament and Character Inventory

Reduced amplitude of the P300 event-related brain potential has been associated with several psychopathological conditions and is thought to represent brain dysfunction in such conditions. Predisposition to personality disorders and psychopathology in general is also associated with low scores on the self-directedness (SD) scale of the Temperament and Character Inventory. The present preliminary study investigated the relationship between amplitudes of P300 elicited by rare target stimuli in a visual oddball task and SD scores in 58 healthy participants. P300 was found to be significantly reduced in subjects with low SD, as supported by correlational analysis and by comparison of groups formed on the basis of SD scores. This finding may be relevant to prior findings indicating reduced P300 amplitudes in a variety of psychopathological conditions and suggests that a common vulnerability factor, reflected in the low SD personality scores, may contribute to the P300 reduction in psychiatric populations.

The neurophysiological meaning of auditory P300 in subtypes of schizophrenia

Event-related potentials are a powerful tool to investigate the real-time course of brain electrical mass activation during cognitive processing. In several psychiatric disorders, differences compared to healthy subjects have been reliably described. The specificity and the pathophysiological meaning of the findings were unclear in most studies, however. This review summarizes methodological aspects and findings, in healthy subjects and psychiatric patients, of investigations based on the auditory oddball paradigm, which evokes the P300 component of event-related potentials. Recent convergent results from P300 and brain imaging studies allowed the interpretation of P300 findings in psychotic disorders in terms of different specific and meaningful neurophysiological disturbances. Namely, core schizophrenia is characterized by a left-temporal dysfunction associated with deficits in verbal processing. Acute remitting schizophrenia-like psychoses (cycloid psychosis, ICD-10 F23), on the other hand, show normal hemispheric balance but consistent signs of cerebral hyperarousal. Recent studies further indicate that the drive for action of manic patients does not rely on over-excitation but rather on frontal disinhibition. The findings may help to further advance the understandings and sub-grouping of functional psychoses based on pathophysiological mechanisms.

Brain mechanisms for detecting perceptual, semantic, and emotional deviance

The observation that we note the exceptional over the mundane has been the subject of extensive psychological and electrophysiological analysis in "oddball" paradigms. Whether detection of a sensory oddball reflects the operation of a generic mechanism or, alternatively, mechanisms sensitive to specific attributes of stimulus deviance is unknown. To address this question we used event-related functional MRI (fMRI) to measure neural responses during presentation of nouns, of which a proportion were perceptually, semantically, or emotionally deviant. Oddballs, regardless of deviant attributes and depth of processing, activated right inferior prefrontal and bilateral posterior fusiform cortices. Attribute-specific responses, independent of depth of processing, were evident in bilateral fusiform cortices for perceptual oddballs and left amygdala for emotional oddballs. By contrast, an interaction with depth of processing was evident in left prefrontal cortex for semantic oddballs. We conclude that detection of oddballs reflects the operation of a generic "deviance detection system," involving right prefrontal and fusiform cortices in addition to specific brain regions sensitive to the stimulus attributes that determine the qualitative characteristics of deviance.

[The p300 cognitive event-related potential. I. Theoretical and psychobiologic perspectives]

The P300 is a positive wave which arises when an attended stimulus is detected. Its parameters depend on a number of variables, in particular the subject's mental state, the task that has to be accomplished, the significance of the stimulus, and the degree of attention. It can be recorded with accuracy, and the different stages of information processing can therefore be analyzed. The P300 wave shows the modifications in neuronal activity which take place during the cognitive process: P300 latency provides an indirect indication of the duration of the processes involved in stimulus discrimination while its amplitude, which is influenced by a number of variables, provides an index of the intensity of the energetic activation or arousal involved. The P300 wave consists of several components which reflect distinct information-processing events (P3a, P3b, P3e, P-SR, P-CR). According to the theoretical models, it is hypothesized that P300 could either represent the adaptation of the working memory to further environmental input ('context updating'), or indicate a closing process ('context closure') in information processing. As regards the physiological aspect of P300 and its association with cortical networks, various studies have suggested that several cortical generators of P300 may co-exist: the medial temporal lobe, the temporo-parietal junction, and the medial and lateral frontal lobe. Psychopharmacological studies have shown that different neurotransmitter systems are involved in the generation and modulation of P300, namely the cholinergic, noradrenergic, dopaminergic, serotoninergic and gabaergic systems. It appears that the noradrenergic agonists increase the amplitude of P300, dopaminergic agonists may have a biphasic effect (increase/reduction), while cholinergic antagonists and gabaergic agonists reduce P300 amplitude and prolong its latency.

The central role of the prefrontal cortex in directing attention to novel events

The physiological basis for the striking decrease of attention to novel events following frontal lobe injury is poorly understood. In this study, event-related potentials (ERPs) were recorded from patients with frontal lobe damage and matched subjects, who controlled the duration of viewing of background, novel and target stimuli. Frontal lobe patients did not differ from normal controls in terms of age, education, estimated IQ or mood. However, they were judged to be more apathetic as measured by self-report and informants' ratings. Patients with frontal lobe damage exhibited markedly reduced amplitude of the novelty P3 response and the duration of viewing of novel stimuli. In contrast, injury to the frontal lobes had a limited impact on P3 amplitude and behavioural responses (viewing duration and reaction time) to target stimuli. A strong correlation was found between measures of apathy and both attenuated P3 amplitude and viewing duration in response to novel but not target stimuli. Differences in amplitude of the novelty P3 response explained a large portion of the variance associated with duration of viewing of novel stimuli. After controlling for the influence of P3 amplitude, there was no association between frontal lobe injury and reduced viewing of novel stimuli. The results of this study suggest that frontal lobe damage leads to diminished visual attention to novel events through its disruption of neural processes underlying the novelty P3 response. These processes appear to regulate the allocation of attentional resources and early exploratory behaviours, and are not limited to immediate orienting responses. Damage to the frontal lobes may prevent the generation of a signal which indicates that a novel event in the environment requires additional attention due to its potential behavioural significance. The disruption of these processes is likely to contribute to the apathy observed in patients after injury to the frontal lobes.

Event-related brain potentials as indicators of smoking cue-reactivity

OBJECTIVE

Reactivity to smoking cues, shown previously by autonomic and self-report variables, was investigated in smokers and nonsmokers using event-related brain potentials (ERPs).

METHODS

Average ERPs to 20 color pictures of people smoking and 20 neutral pictures depicting nonsmoking themes, randomly mixed with 4 repetitions/stimulus, were measured from 20 light-moderate smokers and 18 nonsmokers, following a stressor. Smoker status and stimulus type effects on ERPs and principal components factor scores (FS) were tested by repeated-measures ANOVAs.

RESULTS

Smokers' N268 showed significant medial and midline smoking cue-reactivity (ERP to smoking-related minus neutral stimuli); while a P300-like, P412, showed significant smoking cue-reactivity over medial and left hemisphere scalp. FS analyses confirmed most of the foregoing. P412 smoking cue-reactivity was correlated with unpleasantness-pleasantness cue-reactivity but not with urge-to-smoke cue-reactivity. Nonsmokers' N268 stimulus differences were not significant, but significant P412 stimulus effects (unconfirmed by FS analyses) were found in central-to-posterior and in left parietal-temporal areas.

CONCLUSIONS

Smokers' N268 is identified with a process detecting stimuli incongruent with tobacco-addicted states; and P412 smoking cue-reactivity is discussed in terms of an automatic, perceptual-categorization system, consistent with Tiffany's drug-use and Johnson's P300 models. Implications of ERP smoking cue-reactivity for study of tobacco and other addictions are discussed.

Intracranial ERPs in humans during a lateralized visual oddball task: II. Temporal, parietal, and frontal recordings

OBJECTIVE

We investigated the relative participation of each cerebral hemisphere during a lateralized task that can be performed by a single hemisphere. While our companion article ( Clarke et al. 1999) focused on visual and motor event-related potentials (ERPs) recorded from occipital and peri-Rolandic sites, the present article is concerned with ERP correlates of intermediate stages of information processing from remaining cerebral regions.

METHODS

Intracranial ERPs were recorded from temporal, parietal and frontal lobe sites in 13 patients with intractable epilepsy while they performed a lateralized visual oddball task.

RESULTS

Visually-responsive N2 and/or P3 effects were recorded from medial temporal and supramarginal sites that appear to reflect activity along ventral and dorsal visual streams, respectively. Likewise, certain prefrontal sites, that are probably involved in working memory, were also visually-responsive. The majority of sites exhibiting N2, P3 and/or slow wave components, however, were unaffected by lateralized visual field or response hand effects. Target-evoked P3-like components were most frequently recorded from medial temporal and prefrontal sites. Post-response slow wave components were pervasive, and polarity reversals were present in the insula/operculum region, apparently reflecting somatosensory activity from SII.

CONCLUSIONS

The general absence of lateralized ERP effects despite lateralized stimulus input and response output suggests the importance of interhemispheric integration over hemispheric independence in the processing of this type of task.

Reduced P300 responses in criminal psychopaths during a visual oddball task

BACKGROUND

Clinicians have long recognized that psychopaths show deficits in cognitive function, but there have been few experimental studies exploring these deficits. We present here the first in a series of event-related potential (ERP) experiments designed to elucidate and characterize the neural correlates of cognitive processes of psychopaths.

METHODS

We recorded ERPs from a topographic array from 11 psychopathic and 10 nonpsychopathic prison inmates, assessed with the Hare Psychopathy Checklist-Revised, during performance of a visual oddball task. ERPs to target (25% of trials) and nontarget (75% of trials) visual stimuli were analyzed.

RESULTS

Consistent with previous research, there were no group differences in the latency or amplitude of the ERPs for the nontarget stimuli. For nonpsychopaths, the P300 amplitude was larger when elicited by the target stimuli than when elicited by the nontarget stimuli. In contrast, psychopaths failed to show reliable P300 amplitude differences between the target and nontarget conditions. Psychopaths had a smaller amplitude P300 to target stimuli than did nonpsychopaths. In addition, the amplitude of the P300 was less lateralized in psychopaths than in nonpsychopaths. Psychopaths also had a larger centrofrontal negative wave (N550) during the target condition than did nonpsychopaths.

CONCLUSIONS

The results of this study indicate that there are substantial differences between psychopaths and others in the processing of even simple cognitive tasks and provide support for information processing models of psychopathy.

Functionally independent components of the late positive event-related potential during visual spatial attention

Human event-related potentials (ERPs) were recorded from 10 subjects presented with visual target and nontarget stimuli at five screen locations and responding to targets presented at one of the locations. The late positive response complexes of 25-75 ERP average waveforms from the two task conditions were simultaneously analyzed with Independent Component Analysis, a new computational method for blindly separating linearly mixed signals. Three spatially fixed, temporally independent, behaviorally relevant, and physiologically plausible components were identified without reference to peaks in single-channel waveforms. A novel frontoparietal component (P3f) began at approximately 140 msec and peaked, in faster responders, at the onset of the motor command. The scalp distribution of P3f appeared consistent with brain regions activated during spatial orienting in functional imaging experiments. A longer-latency large component (P3b), positive over parietal cortex, was followed by a postmotor potential (Pmp) component that peaked 200 msec after the button press and reversed polarity near the central sulcus. A fourth component associated with a left frontocentral nontarget positivity (Pnt) was evoked primarily by target-like distractors presented in the attended location. When no distractors were presented, responses of five faster-responding subjects contained largest P3f and smallest Pmp components; when distractors were included, a Pmp component appeared only in responses of the five slower-responding subjects. Direct relationships between component amplitudes, latencies, and behavioral responses, plus similarities between component scalp distributions and regional activations reported in functional brain imaging experiments suggest that P3f, Pmp, and Pnt measure the time course and strength of functionally distinct brain processes.

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.

Executive cognitive functioning in alcohol use disorders

Executive cognitive functioning (ECF) has been identified as an important determinant in the etiology of alcoholism. ECF represents a "higher-order" cognitive construct involved in the self-regulation of goal-directed behavior. The prefrontal cortex and its subcortical connections represent the primary neurological substrate that subserves ECF. Both alcoholics and individuals at high risk for alcoholism exhibit a mild dysfunction in ECF. However, this deficit appears to be significantly stronger in alcoholics with a comorbid diagnosis of an antisocial personality disorder. Individuals with other disorders that are also highly comorbid with alcoholism, such as attention deficit hyperactivity disorder and conduct disorder, also demonstrate deficits in ECF. As such, compromised ECF may not be specific to alcoholism, but instead, might be a potential underlying etiologic substrate for a number of disorders of behavioral excess-disinhibition. Subsequent to reviewing the literature implicating ECF deficits in alcoholism and comorbid disorders, the authors present a heuristic cognitive-neurobehavioral model of alcoholism implicating the frontostriatal system. Finally, recommendations for the prevention and treatment of alcoholism, based on this model, are discussed.

Identification of emotion in a dichotic listening task: event-related brain potential and behavioral findings

The lateralization of emotion perception has been examined using stimuli in both auditory and visual modalities. Studies using dichotic stimuli have generally supported the hypothesis of right-hemisphere dominance for emotion perception, whereas studies of facial and verbal emotion perception have provided evidence for the right-hemisphere and valence hypotheses. A dichotic target detection task was developed to enable acquisition of event-related potentials (ERP) from subjects engaged in emotion detection. Nonsense syllables (e.g., ba, pa) stated in seven different emotional intonations were dichotically presented to 24 young adults, in a target detection task during four separate blocks (target emotions: happiness, interest, anger, or sadness). Accuracy and reaction time and ERP measures were also collected. ERPs were recorded from 14 scalp electrodes with a nose reference and quantified for N100, sustained negativity, late positivity, and slow wave. Significantly greater left- than right-ear accuracy was obtained for the identification of target prosodic emotion. Hemispheric asymmetries of N100 and sustained negativity were found, with left-hemisphere amplitudes greater than right-hemisphere amplitudes. These ERP asymmetries were not significantly correlated with the left-ear dichotic advantage and may be related more to early phonetic processing than to emotion perception. Since the behavioral evidence supports the right-hemisphere hypothesis for emotion perception, behavioral and ERP asymmetries evident in this task reflect separable patterns of brain lateralization.

P3 scalp topography to target and novel visual stimuli in children of alcoholics

The P3 event-related potential (ERP) component was recorded from 7- to 18-year-old children of alcoholics (COAs, n = 50) and age- and sex-matched control children (n = 50) using a visual oddball paradigm, involving nontarget (76%), target (12%), and novel (12%) stimuli. Topographic maps of P3 and associated scalp current density were obtained to supplement a topographic profile analysis. COAs manifested a smaller amplitude P3 to target stimuli over the centroparietal, parietal, and occipital scalp locations than controls. Also, COAs exhibited a smaller amplitude P3 to novel stimuli over the occipital scalp than controls. There were no significant differences between COAs and controls in the P3 scalp topography, indicating that differences in intracranial source strength rather than in source configuration were responsible for the between-group amplitude differences. Also, no significant group differences were observed in the P3 peak latency or in behavioral performance. These results support the notion that the visual P3 may provide a vulnerability marker of alcoholism.