Is the P300 component a manifestation of context updating?

Event-related potentials in Parkinson's disease: a 12-month follow-up study

Auditory event-related potentials were recorded using the oddball paradigm in 26 patients with Parkinson's disease, all treated with L-Dopa. The latency of the P3 wave was significantly greater than in an age-matched controls, and was also correlated with the disease duration, but not with scores on two scales measuring cognitive deficit. One year later, when treatment with a dopaminergic agonist, bromocriptine 20-30 mg/day, had been added to the therapeutic regimen, N2 and P3 latencies had increased, whereas several clinical parameters had improved. Thus a longer P3 latency does not seem to be linked to a global cognitive deficit. The use of neuropsychological tests exploring more limited tasks should show the prospective utility of event-related potentials in Parkinson's disease.

P300 component of the event-related potentials (ERP) during an attention task: effects of age, stimulus modality and event probability

The effects of age, stimulus modality and event probability on event-related potentials (ERP) were studied in 12 young and 12 elderly healthy subjects. The ERP were recorded from 15 electrodes referred to linked ears. Results showed that both amplitude and latency of the P300 component are affected by aging. Study of the latency of the earlier ERP components in the two age groups revealed that the P300 delay was not imputable to a delay of the earlier components. P300 amplitude and latency were also affected by event probability and stimulus modality: infrequent stimulus involved higher and later P300, but this effect was more pronounced in the young than in the old group; higher and later P300 were also recorded during the visual task compared to the auditory. Topographical repartition of the brain wave revealed a predominance of the central sites (Fz, Cz, Pz). The findings are discussed in relation to the sensitivity of the ERP assessment procedures in age related modifications of information processing.

Ongoing ischemic pain as a workload indexed by P3 amplitude and latency in real-versus feigned-pain conditions

We tested four independent groups: real pain, real pain/tracking, feigned pain, and feigned pain/tracking. After baseline (auditory oddball task only, .8/.2), the real pain groups had an ischemia cuff applied, which generated intense pain after 14 min. The pain feigners were instructed to simulate pain. The oddball task was repeated during low pain (6 min following cuff application) and during high pain (7-15 min following application). Real pain ratings were affected by low versus high pain and by tracking (reporting pain regularly), which elevated ratings. Nontracking feigned- and real-pain subjects differed in oddball-evoked P3 amplitude and latency during high pain. Oddball P3 amplitude decreased and latency increased from real low pain to high pain. Tracked but not untracked real low pain affected oddball P3 amplitude. Real and feigned pain-tracking subjects did not differ in P3 amplitude. P3 latency differed between real-pain and feigning subjects during low-pain tracking. A 91% individual hit rate (real vs. feign) obtained.

The effects of attention and context on the spatial and magnitude components of the early responses of the event-related potential elicited by a rare stimulus

Sokolov's (1963) model-comparator theory of orienting and attention theorizes that different events underlie passive and active processing of sensory information presented in different contexts. The following study investigates changes in event-related potentials (ERPs) related to this theory by presenting stimuli inter- and intra-modally during passive and active processing tasks. Model-comparator theory proposes that novel events are detected by a mismatch discrimination process made between incoming and previously presented stimuli during preattentive processing. Central processing is engaged when this mismatch is relevant to the organism. To explore how engaging central processing, induced by instructional priming, affects preattentive processing, a 'truly' passive task was compared with a standard active task. This 'truly' passive task is different from the distracted one normally used to control direction of attention in ERP experiments in that it did not instruct subjects attention towards any task. ERP data were modeled as a dipole whose trajectory moved through voltage space. Our results suggest that both the spatial components and the magnitude of the dipole trajectory changed as functions of both passive and active processing and the context in which stimuli were presented. Our results also suggest that the trajectory and magnitudes of certain ERP components reflect processes proposed by model-comparator theory.

Event-related potentials in high-functioning adult autistics: linguistic and nonlinguistic visual information processing tasks

Event-related potentials (ERPs) were recorded from high-functioning adult autistics and age- and IQ-matched normal controls during performance of two non-linguistic information processing tasks, the Continuous Performance Task (CPT) and Span of Apprehension (SPAN), and an Idiom Recognition Task (IRT) involving idiomatic, literal and nonsense phrases. The autistics exhibited behavioral deficits only when attempting to identify idiomatic phrases. The ERP correlate of that deficit was greatly reduced N400 to idioms. In addition, autistics produced larger N1 amplitudes in all tasks, and larger P3s in the IRT and CPT.

Long latency event-related potentials (P300) in gifted children

In children, P3 latency decreases with increasing age. This decrease could be linked with the maturation of cognitive processes. According to this hypothesis, event-related potentials P3 were recording in gifted children to research an electrophysiological correlation with the mental precocity. Auditory long latency event-related potentials were recorded in 10 gifted children (IQs over 140) and 23 control subjects. The part of variance related to age was extracted by comparing deviations from regression line as a function of age. Stimulus-evoked N1 component latency was not statistically different in the two populations. Event-related P3 component latency was significantly shorter in the gifted children at Cz (P < 0.05). Inter-peak interval N1-P3 was significantly shorter at all three recording sites (P < 0.01 at Fz and CZ, P < 0.02 at Pz). These results suggest a relationship between the P3 component and cognitive ability in children.

Reduced P3b category response in prefrontal patients

Several studies have implicated a frontal/prefrontal contributor to P3b. We hypothesized that prefrontal involvement may be necessary to the processing of novel contextual information, as suggested by selective reduction of P3a in prefrontal patients. ERPs were recorded from 12 controls and 12 unilateral prefrontal lesion patients. In two target-detection tasks, subjects/patients viewed randomly-ordered stimuli drawn from differentially probable categories: numbers (standard, 90%) and letters (deviant, 10%). Topographic and midline analyses were applied to examine target and category effects on P3b. Low-probability targets evoked distinct P3bs in each group. Control subjects' P3bs were additionally enhanced to deviant targets and nontargets. Patients' P3s were enhanced to deviant nontargets but were unaffected by deviant targets. This is consistent with the view that target- and nontarget-evoked P300s are functionally distinct, and suggests that a prefrontal contributor to P3b supports attention to contextual attributes among task-relevant stimuli.

P300, habituation, and response mode

The P3(00) event-related brain potential (ERP) was elicited with an auditory discrimination paradigm under two response task conditions in which the probability of the target tone was always 0.20. Subjects either counted the occurrence of each target tone or pressed a button to the target in different conditions. No response was made to the standard tone. Consecutive blocks of trials were obtained to assess habituation of P3 amplitude. The count task demonstrated less habituation than the button-press task, with a strong interaction obtained between response mode and trial block for all electrode sites. The findings suggest that habituation of P3 amplitude is sensitive to the amount of attentional resources allocated to the processing of a target stimulus, with more resources required for a count task compared to fewer needed for a button-press response.

Latency of P3 in semantic categorization of Chinese characters: preliminary report

ERPs to target stimulation with tone and semantic categorization of Chinese characters were studied in 100 healthy subjects. Age ranged from 40-50 years old (80 subjects) and 50-68 years old (20 subjects). Two hundred Chinese characters were divided into four groups in accordance with the meaning of characters. The probability of each group was 25%. Each group could be used as target stimulus. The latencies of the exogenous components on these two different tasks were the same. The endogenous components on the semantic categorization of Chinese characters were longer than with tone stimulation. In the 40-50 years age group the mean latencies of positive waves at Fz, Cz, C3, and Pz were 546.1034 msec, 547.8621 msec, 548.0345 msec and 547.3103 msec, respectively; latencies in the 50-68 years group were 542.9412 msec, 545.2941 msec, 543.8824 msec and 553.0588 msec respectively. A positive wave, which we called P550 and divided into P550a and P550b, could be recognized in 27.5% of them.

P3 in young boys as a predictor of adolescent substance use

Event-related potentials were recorded during a visual, continuous performance task from 36 boys before use of alcohol or other drugs began. The boys were sons of 13 recovering alcoholics who themselves had a family history of alcoholism, 11 nonalcoholics with a family history of alcoholism, and 12 nonalcoholics with no family history of alcoholism. Four years after electrophysiological assessment, a behavioral questionnaire was administered (mean age = 16.1 years). A Substance Use score was derived from reported use of alcohol and other drugs, and from highly correlated delinquent behavior scores. P3s of lowest amplitude were associated with the highest adolescent Substance Use. The combination of reduced amplitude and prolonged latency of both target and nontarget P3 significantly predicted adolescent Substance Use scores after correction for subjects' age. Although this is the first electrophysiological predictor of adolescent substance use we are aware of, the effect was small, indicating the utility of P3 as a vulnerability marker for substance abuse disorders is likely to depend on its joint use with other measures.

Event-related potentials in methamphetamine psychosis during an auditory discrimination task. A preliminary report

Auditory event-related potentials (ERPs) during a syllable discrimination task were recorded from 15 patients suffering from methamphetamine (MAP) psychosis after the remission of acute psychotic symptoms, and from 15 normal age-matched controls. Subjects were instructed to press a button in response to the target syllables applied to one designated ear. In MAP psychotics, the attention-related negative components (Nd) area was reduced and P300 latency was delayed compared with normal controls. MAP psychotics and controls did not differ significantly in P300 amplitude. These findings suggest that MAP psychotics show some impairment in the auditory information processing.

AERPs and clinical evolution of thought disorders over five years

In a selective attention task, 21 Subjects detected rare randomized targets (P = 0.02) in a set of randomized standard tones. In one condition, Subjects focused their attention and detected targets in one ear, ignoring the other ear, and vice versa in the next condition. AERPs (auditory event-related potentials) were recorded at 5 electrode sites (10-20 system), at Fz, Cz, Pz, C3, C4, in two conditions varying speed of stimulation (randomized interstimulus intervals of 250-750 ms and 750-1500 ms). One group of 7 schizophrenics with the major syndrome of formal thought disorder (+FTD) was compared to 7 schizophrenics without the FTD syndrome (-FTD), and to 7 controls. The schizophrenic group was matched for age, education, sex, medication, hospitalization and intelligence score on abbreviated WAIS test. Ss were re-tested after 5 years following identical experimental and counterbalancing method to the pre-test. At re-test, similarly to pre-test, schizophrenics' AERPs showed smaller amplitudes, longer latencies, smaller attention effects than normals. -FTD schizophrenics showed intermediate values between the +FTD patients and normals. At retest, +FTD schizophrenics showed an aggravation of these AERP abnormalities while -FTD patients seemed to improve with larger amplitudes, faster latencies and better attention effects than at pre-test. Differential correlations between clinical and AERP indices indicated a dissociation between neurophysiological and clinical evolution: factors of dissociation included Andreasen's positive and negative indices of thought disorder, neuropsychological indices on the Luria-Nebraska scales, and severity of psychotic symptoms.

The scalp topography of P300 in the visual and auditory modalities: a comparison of three normalization methods and the control of statistical type II error

This study was designed to replicate recent findings suggesting that the P3 component of the event-related potential is dependent on the modality of the eliciting stimulus. When assessing this research hypothesis two methodological problems are of special interest: first, the amplitudes have to be normalized, due to problems with the model of the analysis of variance; second, special care has to be taken regarding the beta error, which is the probability of falsely accepting the null hypothesis of a statistical test. A possible modality independence is associated with the acceptance of a null hypothesis. The first problem was assessed by using different normalization procedures and comparing their results. The second was solved by controlling the beta error. Results for P3 amplitudes from two sessions in which 61 subjects performed in each session an auditory and a visual oddball task (EEG measured at 11 locations) showed no influence of modality on the P3 elicited by the rare, task relevant, stimulus. Influences of modality were observed for the P3 elicited by the frequent stimulus. As it is quite unlikely that P3 generating sources are strongly active during the processing of the frequent stimulus, this effect is possibly due to a component overlap from the vertex potential.

Time effects on event-related brain potentials and vigilance performance

A review of the literature showed that in vigilance or oddball tasks, changes over time in event-related potentials (ERPs) and performance measures often seem to be unrelated, but a number of studies had some shortcomings. In the present study a visual vigilance experiment was carried out, in which single-trial ERPs and performance data of 40 males were obtained. A relationship between time trends in behavioral and ERP measures was found: an early P3 amplitude and response latency (RT) showed an inversely varying relation over time. Analysis of covariance showed that the two linear trends tap the same aspect of processing: both trends became insignificant when adjusted for common variance. A negative correlation between mean values of P3 amplitude and RT rather than for change scores has been observed in previous studies, but has been ignored in the literature. However, correlations with RT have also been reported for other ERP deflections. Although there were several correlations between mean scores, most time-induced changes in ERP parameters appeared to be unrelated to worsening performance, for which several explanations are advanced. The ERP results do not support the hypothesis that a decrement in performance is caused by increasing difficulty discriminating targets from nontargets. A gradual decline in effort or resources allocated to the task might be an alternative explanation of performance deterioration. However, an effort-hypothesis cannot easily be tested. Effort is often invoked post hoc, and has previously been associated with many ERP components. The relationship between ERPs and the signal detection measures "sensitivity" d' and "response bias" beta is discussed.

Neural and behavioral correlates of emotion recognition in children and adults

Event-related potentials (ERPs), accuracy scores, and reaction times were used to examine the recognition of emotional expressions. Adults and 7-year-old children saw upright and inverted chromatic slides of the facial expressions of happiness, fear, surprise, and anger, and were asked to press a button for either "happy" or "angry" faces. A positive-going waveform (P300) was apparent at parietal scalp (Pz) and at left and right temporal scalp. Although the behavioral data were similar for both children and adults (e.g., both had more difficulty recognizing angry expressions than happy ones, and angry expressions were more difficult to recognize upside-down than were happy faces), the ERPs indicated that children responded differently than adults did to happy and angry expressions. Adults showed greater P300 amplitude to happy faces, while children showed greater P300 amplitude to angry faces. In addition, for adults, but not children, there were greater P300 amplitude responses at right vs. left temporal scalp.

Attention and para-attentional processing. Event-related brain potentials as tests of a model

In 1972 when we began to analyze the vast amount of material from the laboratories of physiological psychologists, we had only a vague conceptualization of what a model of attention might look like. We began where everyone else had, with the view that everything had something to do with "arousal" but with Lacey's (1967) warning in mind that all of the dependent variables might not actually be measuring aspects of the same process. With this warning in mind, we were forced by the data to organize them into a three-systems mode. Since the first publication of this model in 1975, we have found increasing amounts of evidence to support and extend it. This evidence is briefly reviewed in the present paper in terms of the techniques employed in various types of investigation. Further, the current review of data has made it possible to specify the para-attentional substrate (the extrinsic lemniscal primary projection systems) upon which the three systems described in the earlier model operate. The earlier model was based on psychophysiological, neurobehavioral and neurochemical analyses while the current specification results from the results of recordings of event-related brain electrical responses. The conclusions derived from these results can be summarized as follows: First. It has become possible to distinguish controlled attention from the para-attentional pre- and post-attentive automatic processes upon which controls operate. Second. The pre- and post-attentive processes appear to be coordinate with activity in the extrinsic lemniscal primary sensory projection systems. Processing in these systems is reflected in the early components of event-related brain electrical potentials. These extrinsic systems are, however, not just throughputs for further processing. Rather, they are sensitive to the history of reinforcement which the subject has experienced. The concept of a limited channel capacity must, therefore, be modified to encompass this ability of organisms to improve, through practice, their competence to process a great deal of information in parallel. Competence, not capacity, limits central processing span. Third. A set of intrinsic extralemniscal processing systems has been identified to operate via a tecto-tegmental pathway to the reticular nucleus of the thalamus. The later components (N2P3, etc.) of event-related potentials have been shown to reflect processing in these systems and those that control them. Activity in these systems has been related to targeted conscious awareness.(ABSTRACT TRUNCATED AT 400 WORDS)

Event-related EEG potentials in mild dementia of the Alzheimer type

Most studies on event-related EEG potentials in dementia have focussed on the P3 component and used auditory stimuli only. In the present study, N2b was analysed in the usual auditory oddball task in addition to P3, and a visual task was employed ("Push"/"Wait"), with recordings including an occipital scalp site. Seven Alzheimer-type patients, with their mean IQ still in the normal range, were compared to age-matched normal controls. In the oddball task, P3 did not differ between groups but the patients' N2b was delayed. The main difference in the Push/Wait task was in an occipital P270, which component was distinctly larger in the patients. It is suggested that both differences reflect the disintegration of patients' cognition: stimuli are perceived in a normal way but then a gap arises due to uncertainty what to do with the perceived event.

Abnormal cerebral laterality in bipolar depression: convergence of behavioral and brain event-related potential findings

Cerebral laterality in bipolar and unipolar major depression was compared using visual half-field and dichotic listening measures of perceptual asymmetry. The results replicate our prior finding of abnormal laterality in bipolar depressed patients on a visuospatial test. Bipolar patients (n = 11) failed to show the left visual field (right hemisphere) advantage for dot enumeration seen for both unipolar patients (n = 43) and normal controls (n = 24). Bipolar patients performed significantly poorer than unipolar patients on normal controls for left visual field, but not right visual field stimuli. An electrophysiological correlate of abnormal visual field asymmetry in bipolar depression was found in brain event-related potentials recorded during audiospatial and temporal discrimination tasks. Bipolar patients had smaller N100 amplitudes for test stimuli in the left than right hemifield, whereas unipolar patients and normals did not. The origins of left hemifield deficits in bipolar depression are discussed in terms of right-sided dysfunction of an arousal/attentional system involving temporoparietal and possibly frontal regions.

Event-related potential investigations of cognitive development and aging

Comparison of the results of the studies of cognitive development and normal aging suggests a large degree of commonality in both behavioral and ERP effects across a wide age range. Whether measured in young children, adolescents, young, middle-aged or elderly adults, the size of the ERP repetition effect did not differ among the various age groups. This was true whether memory was tested directly during continuous recognition or indirectly during variants of semantic categorization tasks. Similarly, in the studies of adult aging, the degree of RT facilitation during the semantic task did not differ with age and, in both the studies of cognitive development and aging, the degree of RT prolongation during the explicit tasks did not appear to differ as a function of age. Moreover, in the studies of adult aging, the effects of three versus two exposures of a word assessed in the PM session (TABLE 1), modulated RT similarly in all three age groups. These data argue for continuity of information processing across a very wide age range during both direct and indirect memory tasks, when retention is assessed during the recognition (for explicit testing) and repetition (for implicit testing) phases of the task. Since ERP and RT modulation do not appear to differ with age during the retrieval phases of these experiments, how can the performance differential seen in young children and older adults be explained? Some evidence comes from the ERP data recorded during the study phases of our explicit tasks. During continuous recognition, both young children and elderly adults did not show the typical subsequent "memory effect." In the case of the children, the subsequently unrecognized ERP was larger than the subsequently recognized ERP, whereas for the older adults, there was no difference between these two ERPs. Moreover, during these same tasks, the young children did show the "crossover" (new greater than old) pattern for slow wave activity, whereas the older adults did not. Since these ERP findings were obtained during the acquisition phase (i.e., to new items that had to be encoded for subsequent retrieval), the data argue for encoding difficulties as one means of explaining the performance differences seen at the two ends of the age spectrum. However, since the older adults displayed a different new/old pattern for slow wave activity, the two age groups may differ qualitatively in the strategies employed to encode items for subsequent retrieval.(ABSTRACT TRUNCATED AT 400 WORDS)

ERP components related to stimulus selection processes

Event-related potential (ERP) components associated with target stimulus selection in a double discrimination visual task were studied. The experimental paradigm consisted in the presentation of low intensity stimuli that varied according to two physical features: geometrical form (squares and circles) and location (a spot in different positions inside the stimulus). Subjects performed 3 tasks on these stimuli: control task in which they looked passively at the stimuli, and 2 discrimination tasks, in which they had to respond to a certain stimulus (a specific conjunction of form and spot location). The early components (P1 and N1) obtained in the control and discrimination tasks were associated with sensory analysis of simple stimulus features. Relevance of a particular feature modified the latency and/or the area of these components. The longer-latency components (N2 and P3) were elicited only in the discrimination tasks. N2 was associated with target stimulus selection because its area was significantly larger for target stimuli and because its "offset" latency correlated with choice reaction time. Results are discussed and contrasted with various models of target selection.

P300, probability, and introverted/extroverted personality types

Extreme introverted and extroverted subject groups (n = 24 each) containing equal numbers of male and females were assessed with the P300 (P3) component of the event-related potential (ERP). A two-tone auditory discrimination task in which the probability of the target stimulus varied systematically in different conditions (.20, .40, .60, .80) was used to elicit the ERPs. The P3 amplitude demonstrated a significant interaction between personality type, probability, and subject gender and was generally smaller for introverts than for extroverts. Female subjects tended to have larger overall P3 components than male subjects. P3 latency was not affected by the personality variable. The results support previous findings for ERP differences between introverts and extroverts and suggest that personality type differentially influences target stimulus probability effects. The findings are discussed in terms of individual differences in cortical activity on P3 amplitude and personality measures.

Event-related potentials in the dual task paradigm: P300 discriminates engaging and non-engaging films when film-viewing is the primary task

Five groups of subjects (11-16/group) were run in three experiments. In each study P300 amplitude and latency were studied as a function of three sensory task conditions: (1) baseline (oddball task: target and non-target tones only); (2) boring film viewing plus oddball task; and (3) exciting film viewing plus oddball task. In Experiment I, target probability was P = 0.22. In Experiments II and III, each of two groups of subjects was run at P = 0.22 or P = 0.33. Two different exciting films and two different boring films were used. Oddball-target amplitude was found to consistently decrease from baseline to boring to exciting film-viewing conditions at P = 0.22. At P = 0.33, the 2-film discrimination was successful in one of two experiments. P300 amplitude consistently differed from baseline to film-viewing conditions. For the non-target (frequent) tones, the smaller P300 amplitudes consistently discriminated boring and exciting films, as well as single from dual tasks. For target P300 latency, single (baseline) and dual (film-watching) conditions were always discriminable, but boring and exciting films were not discriminable. There were no effects on non-target P300 latency. N100 amplitude discriminated baseline and film viewing conditions, but not boring and engaging films.

Operant conditioning of P300

This study demonstrates that operant conditioning may increase the P300 component of the event-related potential above a level obtained without contingent training. An experimental group of subjects was rewarded for producing large P300 amplitudes and was compared with a yoked control group which was rewarded on a random basis. During training the experimental subjects increased both the amplitude of the P300 and of a subsequent frontal negative slow wave relative to the control group. These training effects were independent of prestimulus potential shifts and occurred likewise for target and nontarget stimuli.

Neural and behavioral correlates of visual recognition memory in 4- and 8-month-old infants

The neural and behavioral correlates of the 4- and 8-month-old infant's ability to distinguish between frequently and infrequently presented familiar and novel events was examined. Cortical event-related potentials (ERPs) were recorded as infants were familiarized to two faces. During the test trials that followed, one of these faces was presented frequently, and the other infrequently; on each of the remaining 20% of the trials, a previously unseen, novel face was presented. Following the ERP phase, infants' looking times were recorded to pairs of faces, some of which had been seen during the ERP testing, and some of which had not. At 4 months the ERP activity invoked by the three classes of events was similar, suggesting that infants were unable to distinguish among them. At 8 months the ERP activity differed only between the Infrequent Novel events and the two classes of familiar events, but did not differ between the frequently and infrequently presented familiar events. The ERP findings complement previously reported data from 6-month-old infants in describing a trend whereby infants become increasingly able to respond to stimuli on the basis of whether they have been seen before, and not on the basis of how often they had been seen. The behavioral data at both 4 and 8 months were less clear cut than the ERP data. These findings are discussed in the context of the neural and cognitive processes involved in dissociating probability information from novelty detection.

Potentials evoked in human and monkey medial temporal lobe during auditory and visual oddball paradigms

Event-related potentials (ERPs) were recorded from epileptic patients with electrodes chronically implanted in the medial temporal lobe (MTL) and other intracranial locations, and from monkeys with epidural, transcortical, and MTL electrodes. For both humans and monkeys, the eliciting events consisted of trains of auditory or visual stimuli in which a random 10-20% deviated in pitch or pattern from the remaining stimuli. The distribution of ERPs elicited by the rare (oddball) stimuli in both species was similar, consisting of a P3 recorded from the scalp or cortical surface and a slightly later, but temporally overlapping, focal negativity in the hippocampus and nearby MTL structures. The similarity between the patterns of ERPs in humans and monkeys establishes the feasibility of studying the electrogenesis of P3-like activity with detailed intracranial recordings in an animal model. The data also establish that the MTL ERPs in human patients represent a normal neurophysiological process unrelated to epilepsy.

P300 and conceptual loosening in normals: an event-related potential correlate of "thought disorder?"

Reduced amplitude of the P300 component of the event-related potential (ERP) has frequently been reported in schizophrenic patients and their first-degree relatives. The present study examined the relationship between this ERP measure of attentional processing and loosening of associations in normal university students (termed "allusive thinking"). Among male subjects, scores reflecting increased conceptual loosening, measured using the Lovibond scoring method for the Goldstein-Scheerer Object Sorting Test (OST), were significantly correlated with smaller P300 amplitude recorded during an auditory target detection task. There was no association between OST score and either performance of the target detection task or self-reported psychopathology. It is suggested that reduced P300 amplitude could reflect altered attentional processing in individuals with a constitutional trait factor of thought disorder.

Comparison of infant and adult P300 from auditory stimuli

Event-related brain potentials (ERPs) using auditory stimuli were recorded from 5- to 10-month-old infants and normal young adults with a passive tone sequence paradigm. A P3 (P300) component was obtained which demonstrated the same central-parietal maximum scalp distribution for both subject groups. P3 amplitude was smaller and its peak latency longer for infants compared to those of the adults across all electrode sites. P3 measures remained stable across stimulus trials indicating that ERP habituation was not occurring. Evaluation of individual subjects suggests that the P3 can be elicited from infants with auditory stimuli in a manner similar to that from adults and may serve as a useful index for the assessment of cognitive function in infants.

Changes in cortical activity when subjects scan memory for tones

The magnetoencephalogram (MEG) was used to detect regional changes in spontaneous cortical activity accompanying short-term memory search. This method was chosen because magnetic fields are detectable only within a few centimeters of the projections of their sources onto the scalp. The specific hypothesis that auditory cortex is involved in scanning memory for tones was tested by sensing the field of the magnetic counterpart to N100 (N100m) which is known to originate in auditory cortex. N100m was measured at many different positions and the spontaneous cortical rhythms in the alpha bandwidth (8-12 Hz) were measured at the same places. These rhythms were found to be suppressed while subjects scanned memory for musical tones in a Sternberg paradigm. For 3 subjects, both the MEG suppression time (ST) and reaction time (RT) increased linearly with memory set size. The correlation between ST measured over the left hemisphere and set size was significant for two subjects but not significant for the third, and the slopes of the regression lines relating ST to set size were too shallow to be related to the time required to scan memory. However, the correlation between ST of the right hemisphere and set size was highly significant for all subjects, and the slopes of the regression lines were comparable to those relating RT to set size. The electroencephalogram (EEG) recorded with midline electrodes failed to reveal a significant relationship between suppression time and set size for 2 of the subjects, thus ruling out global alpha blockage and generalized arousal as the basis for the task-related suppression duration. The electric N100, measured at Cz, decreased significantly in amplitude with set size for 2 subjects, but it increased significantly in amplitude for the third subject. In contrast, RT increased with set size for all subjects. N100m measured over the right hemisphere was similar to the behavior of N100, while N100m measured over the left hemisphere showed little change in amplitude with set size, thus establishing an asymmetry in N100 between the hemispheres. Since N100 amplitude is normally larger when attention is paid to auditory stimuli, differential attention alone cannot account for the relation between ST and set size. Furthermore, the processing negativity, which may be superimposed on N100 in selective attention tasks, was not discernible for any set size. It was also found that ST prior to the button press was not correlated with RT. Hence, the covariation of set size with ST is not attributable to preparation for a motor response.(ABSTRACT TRUNCATED AT 400 WORDS)

P300 in multiple sclerosis: a preliminary report

The P300 component of the event-related brain potential (ERP) elicited with auditory stimuli and pattern-shift visual evoked potentials (VEPs) was obtained from 16 patients with multiple sclerosis (MS) and 16 matched control subjects. P300 latency was significantly longer and component amplitude relatively depressed in the MS patients compared to control subjects. The P100 potential of the VEP also was delayed for both full-field and half-field stimulus conditions in the patients compared to control subjects. The findings suggest that the P300 ERP may reflect the cognitive decline associated with MS.

P300 and individual differences: morning/evening activity preference, food, and time-of-day

To determine how individual differences stemming from activity preference, previous food intake, and time-of-day affect the P300 or P3 event-related brain potential (ERP), subject groups who varied orthogonally on these factors were compared using a simple auditory discrimination task to elicit the ERPs. Amplitude of the P3 component for morning-preferring subjects who had eaten recently was relatively large for both the morning and evening measurement time groups. P3 amplitude for the morning-preferring subjects who had not eaten recently was large for those measured in the morning and relatively small for those subjects measured in the evening. For evening-preferring subjects who had eaten recently, P3 amplitude was again relatively large for both the morning and evening measurement time groups. Evening-preferring subjects who had not eaten recently produced very small P3 components for those measured in the morning compared to the large components produced by those subjects measured in the evening. P3 latency tended to be longer for all subjects who had not eaten recently compared to those who had. The results suggest that the P3 component is sensitive to physiological and psychological changes originating from individual differences related to bodily state, which perhaps stems from individual differences in arousal level.

Effects of isolated and combined exposures to whole-body vibration and noise on auditory-event related brain potentials and psychophysical assessment

Auditory event-related brain potentials (ERP) in response to two different tone stimuli (1.1 kHz or 1 kHz, 80 dB, 50 ms; given by headphones at a regular interstimulus interval of 5 s with a probability distribution of 70:30) were recorded from 12 healthy male subjects (Ss) during four different conditions with two repetitions: A-60 dBA white noise (wN), no whole-body vibration (WBV); B-60 dBA wN plus sinusoidal WBV in the az-direction with a frequency of 2.01 Hz and acceleration of 2 m.s-2 root mean square; C-80 dBA wN, no WBV; D-80 dBA wN plus WBV. Each condition consisted of two runs of about 11 min interrupted by a break of 4 min. During the break with continuing exposure, but without auditory stimuli, Ss judged the difficulty of the tone-detection task and intensity of noise by means of cross-modality matching (CMM). Vibration-synchronous activity in the electrocardiogram was eliminated by a subtraction-technique. Noise caused an attenuation of the N1 and P2 amplitudes and prolongation of P3 latencies. The WBV did not cause systematic ERP effects. Condition B was associated with higher N1 and smaller P3 amplitudes. The factor "condition" had a significant effect on the peak latencies of P3 to target stimuli and the task difficulty judged by CMM. Both effects exhibited significant linear increases in the sequence of conditions A, B, C, D. For the evaluation of exposure conditions at work, it can be suggested that noise has a strong systematic effect which can be enhanced by WBV.(ABSTRACT TRUNCATED AT 250 WORDS)

P300, food consumption, and memory performance

The effects of food intake on the P300 (P3) component of the event-related brain potential (ERP) were assessed in two studies. Experiment 1 compared 24 subjects who had not eaten within 6 hours of testing with 24 subjects who had consumed food within 3 hours of testing. P3 target stimulus amplitude was reduced significantly for the subjects who had not eaten relative to those who had eaten, whereas peak P3 latency was only moderately affected by the recency of food consumption over task conditions. In Experiment 2, P3 measurements, memory performance in a word recall task, and blood glucose levels were obtained from 24 subjects at three different times: 1) after a 14-hour fast, 2) 5 min after consuming lunch, and 3) 30 min after consuming lunch. P3 target stimulus amplitude increased initially after food intake and decreased slightly at the third measurement time, while peak P3 latency became somewhat shorter immediately after food intake but then returned to baseline. Recall for recently presented items mimicked the P3 amplitude changes, whereas blood glucose levels increased monotonically across food conditions. The results from both studies suggest that: 1) target stimulus P3 amplitude is affected by the recency of food intake; 2) food-related P3 amplitude changes appear related to memory function; and 3) subjects should eat within several hours before ERPs are acquired to ensure that P3 component measurements reflect values indicative of normal bodily functioning.

On the reasons for the delay of P3 latency in healthy elderly subjects

The P3 component reaches its peak later in elderly subjects than in young subjects. The aim of this study was to repeat this finding in the usual auditory oddball task and to look for reasons for the delay by analysing other components and by applying another task, the visual Push/Wait task. It was found in the oddball that the age delay was present for mismatch negativity already but further increased until P3's peak. In the Push/Wait task, the size of the age delay was independent of another delay caused by reduced visual intensity of the stimuli. Further, the age delay had its onset after the occipital P140 component whereas the intensity delay was present before this component. Within the elderly, P3 latencies correlated between the auditory and the visual tasks, and the common factor extracted from both latencies correlated with a test of short-term memory span. It is concluded that the age delay of P3 is not due to a delay of perceptual encoding but perhaps due to delayed memory processes in the elderly. As usual, P3 amplitudes were larger and more parietally focussed in the young than in the elderly. Possible differences in motivation might account for this finding.

Probing the time-course of the auditory oddball P3 with secondary reaction time

An elementary neural model of the P3 is proposed in which the P3 is held to manifest a brief, widely-distributed, inhibitory event. A preliminary and indirect test of the model is described using secondary-task methodology. Manual reaction times were measured to probe clicks delivered during the presumed time-course of an auditory oddball P3. We observed that reaction times to probes presented after oddball stimuli were significantly slowed as compared to reaction times to probes presented after standards. The latency of maximum reaction time slowing corresponded generally to the latency of the P3. The latency of maximum reaction time slowing did not respond to a manipulation varying the latency of the P3. Thus, some of the obtained results were consistent with the P3-inhibition hypothesis, whereas others were not. Secondary-task methodology may provide a valuable new approach to understanding the late event-related potentials.

P300 seasonal variation

The P300 (P3) event-related brain potential (ERP) was elicited with auditory stimuli in four different groups of normal, young adult subjects (n = 20 in each group) whose ERPs were obtained at different times of the year. P3 amplitude was largest during spring and summer and smaller for the subjects who were assessed during fall and winter. P3 latency was not affected reliably by changes in the seasons. Measurement of the daily sunshine present when each subject was recorded indicated that P3 amplitude is influenced by seasonal variation in the available amount of sunshine. These findings suggest that comparison of P3 amplitude across subject groups must take seasonal differences into account.

Active and passive attention in schizophrenia: an ERP study of information processing in a linguistic task

Attentional dysfunctions in schizophrenia were investigated using a sentence priming task. Schizophrenic patients and healthy control subjects were presented with sentences to which they were required to make a response based on either semantic or physical stimulus features. Schizophrenics' behavioural responses were slower than those of controls, particularly when attending to semantic relationships, but their performance was no less accurate. Both the P300 and the N400 components of the event-related potentials (ERPs) recorded to the sentence completions were attenuated in the schizophrenic sample. The results are interpreted in terms of a deficit in the active maintenance of semantic information in memory and the integration of new information with this representation.

Discovery of the P300: a tribute

The significant and enduring contributions made to cognitive psychophysiology by Samuel Sutton and his colleagues in the first two papers on the P300 component of the event-related brain potential are discussed. The remarkable quality of these contributions is revealed in the fact that the issues that motivated the series of experiments reported by these investigators continue to be of core importance to the field.

Auditory event-related potentials in obstructive sleep apnea: effects of treatment with nasal continuous positive airway pressure

Event-related potentials (ERPs) were recorded in 47 patients with obstructive sleep apnea (OSA) syndrome prior to and after 6 weeks of treatment with continuous positive airway pressure (CPAP). Compared with a control group, the OSA patients showed ERP abnormalities: lengthened P3 latencies and decreased N2-P3 amplitudes. After 6 weeks of CPAP treatment, there was a highly significant improvement in the abnormal ERPs: the P3 and N2 latencies were shortened, but remained longer than in controls, and the N2-P3 and N1-P2 amplitudes were increased. No correlations could be established with various sleep variables. ERPs may be used as an electrophysiological marker of brain dysfunction; treatment of OSA with CPAP is probably responsible for functional brain modifications. On the other hand, possible relationships between the ERP abnormalities and the neuropsychological disorders observed in OSA remain to be established.

Event-related potentials in alcoholic fathers and their sons

ERPs were recorded during a simple color discrimination and a more difficult visual continuous performance task (CPT) from three father-son (n = 15) pair groups: recovering alcoholics with a family history of alcoholism and their sons (A+), nonalcoholics with a family history of alcoholism and their sons (NA+), and nonalcoholics with no family history of alcoholism and their sons (NA-). The sons, aged 8 to 12, had not begun drinking or using other drugs. Groups were matched on age, education and socioeconomic status. There were two principal findings. Compared to nonalcoholic groups, both A+ sons and fathers exhibited increased latency and decreased amplitude of P3 for the difficult task, but not for the easy task. This result helps to explain previous inconsistencies in the literature, and strengthens the suggestion that one indication of a vulnerability to develop alcoholism is an abnormal P3, when elicited by an appropriate task. Additionally, A+ fathers had more negative amplitudes for a late slow wave in both tasks, suggesting electrophysiological consequences of long-term alcohol abuse.

The relationship between menstrual phase and the P3 component of ERPs

Event-related potentials (ERPs) and behavioral ratings were collected from 30 female subjects who were exposed to picture slides. The slides belonged to five affective categories whose content was babies, dermatological cases, ordinary people, male models, and female models. Based on the day of testing relative to their menstrual cycle, the subjects were grouped according to their expected levels of androgens, estrogen, or progesterone. The data were examined to determine whether any ERP component or behavioral rating (non-erotic/erotic, unpleasant/pleasant, simple/complex, and low arousal/high arousal) varied as a function of subjects' hormone defined menstrual phase. Only the P3 component was sensitive to menstrual phase. The P3 to babies and male models was largest when progesterone levels were high. High progesterone was also associated with a decrease in the complexity and eroticism of all slide categories. An increase in the pleasantness of all categories was evident when estrogen levels were high. The results are interpreted as support for an "adaptive context updating" theory of the P3 component of ERPs.

The waltzing oddball

We investigated whether task relevance and probability interact to influence P3 amplitude. High and low tones were presented in random order with equal probability. In the control condition (standard oddball), every high tone had to be counted. In the waltz condition, high tones had to be counted only if they were preceded by two other high tones. It was predicted that the P3s evoked by targets in the waltz condition would be larger than the P3s evoked by the same sequence of targets in the oddball condition. That is, the frequency of occurrence of the targets should have an effect on P3, in addition to effects of the frequency of stimulus occurrence and stimulus task relevance (target/nontarget). This prediction was upheld. However, the largest P3s were evoked by nontargets following two high tones in the waltz condition. These P3s had a more anterior topographic maximum than usual. We contend that these anterior P3s reflect the interruption of an ongoing task and cannot be easily fit into the framework of the two concepts of task relevance and probability.

Effects of crossmodal divided attention on late ERP components. II. Error processing in choice reaction tasks

Reaction times and event-related potentials in correct and incorrect trials were studied in a bimanual choice reaction task. In a focused attention (FA) condition, the stimulus modality was constant (visual or auditory); in a divided attention (DA) condition, the modality was varied at random from trial to trial. Stimulus- and response-triggered averages were computed from the midline EEG leads. In error trials, the ERP amplitude was reduced in the P300 range (300-500 msec) and enhanced in the slow wave range (500-700 msec) compared to correct reaction trials. Difference plots between the ERPs (incorrect minus correct reaction trials) revealed a large fronto-central negativity ("NE") and a parieto-occipital "slow wave." These components appeared larger in the response-triggered averages. We believe that they reflect two different stages of error processing. After auditory stimuli the NE peaked much later for DA than for FA, which supports the idea of an asymmetrical allocation of processing resources to the disadvantage of the auditory modality in our DA condition.

Effects of crossmodal divided attention on late ERP components. I. Simple and choice reaction tasks

We studied several effects of dividing attention between visual and acoustic inputs on different processing stages. Simple and choice responses were required to single letter stimuli. RTs and P300 latencies were delayed for divided attention (variable stimulus modality) as compared to focused attention (constant stimulus modality). In all but one condition, RT and P300 delays were similar. The exception was choice tasks to auditory stimuli, in which the RT delay was far larger than the P300 delay. Since the amplitude of the late ERP was larger in choice tasks than in simple tasks, the differences between the ERPs of choice and simple tasks were computed. They revealed that an additional late positive wave ("P-CR") occurred in all choice ERPs. In the divided attention condition the auditory (but not the visual) P-CR showed a longer delay compared to focused attention. We interpret the P-CR to be time-related to the response selection process. Our results suggest that the division of attention causes a slight impairment of stimulus evaluation (shown in P300 latency) and, after auditory stimuli only, a strong impairment of response selection (shown in P-CR latency). We therefore conclude that the observed RT effects are due to a bias of processing resources towards the visual modality, which mainly affects response selection. The results are in accordance with the theory of visual dominance.

Event-related potentials and eyeblink responses in automatic and controlled processing: effects of age

Seventeen young (mean age = 20.2 years old) and 16 elderly (mean age = 72.6 years old) women were tested with event-related potential (ERP) paradigms designed to elicit responses in reaction time tasks and to a startling noise burst. EEG was analyzed from 17 standard 10-20 electrode sites. Reaction time and performance data suggested that the elderly did not perform worse than the young. Nevertheless, the physiological responses of the elderly differed significantly from those of the young. While the task-dependent P3s at Pz were smaller in the elderly than in the young, the automatic P3 was smaller yet. The distribution of both types of P3 across the scalp was more uniform in the elderly than in the young. Single-trial analyses revealed that the P3 amplitude differences at Pz were not due to latency dispersal of single trials. Single-trial startle eye blink responses to intense noise bursts during the automatic paradigm were considerably less frequent in the elderly, although their individual startle blinks were actually larger. The data demonstrate that the electrophysiological responses of the elderly are different from the young both in tasks eliciting automatic responses and in tasks requiring controlled processing.