P300 Amplitude Differences Research Articles

Topography of auditory and visual P300 in normal children.

Auditory and visual P300 recordings were performed on 39 normal, right-handed individuals from age 6 through 15, using 31 evenly spaced scalp electrodes. Amplitude at the P300 peak and latency to this peak at each electrode site were measured. Age was significantly correlated with the 31-electrode mean for auditory and visual P300 latencies, but not for amplitudes. The younger age group (6-10) had longer auditory and visual P300 latencies than the older age group. Visual P300 amplitudes were of an overall larger magnitude than auditory amplitudes. There were no other differences including significant topographical differences in P300 amplitudes or latencies by gender, age group, modality, or side of scalp. Radial current density maps on group-averaged auditory and visual P300 waveforms at the group mean P300 latency at Cz, showed a right centroparietal sink surrounded by sources. This suggests a major right centroparietal P300 generator. Description of the normal topography of the P300, and demonstration of the lack of topographic differences by gender, age group, modality, or side of scalp, may facilitate the meaningful examination of P300 topography in cognitive disorders. Such an examination might lead to better diagnostic tools and more appropriate treatment of cognitive disorders in children.

Event-related potentials in alcoholic men, their high-risk male relatives, and low-risk male controls.

A total of 217 adult male subjects were evaluated utilizing event-related potentials (ERPs) elicited with two different auditory tasks (Counting and Choice Reaction). Ninety-eight alcoholics from high-density, multigenerational families were evaluated along with 39 first-degree nonalcoholic relatives from the same high-density families. Eighty controls, selected for low density of alcoholism in their extended families, were also studied. Using both conventional and topographic analyses, no significant differences in the amplitude of the P300 component could be found with either of the auditory tasks. No significant differences in amplitude of N250 were seen. The latency of N250 increased with increasing conditional probabilities (0.33, 0.67, and 1.00), a trend that was amplified in the Counting task as compared with the Choice Reaction task. This prolongation in a task not requiring a reaction response (button press) tended to increase the latency more for alcoholics than controls or high-risk nonalcoholic subjects. Age, lifetime, and recent drinking were treated as covariates in all analyses. The absence of P300 amplitude differences between adult high- and low-risk subjects is discussed in the context of the much more reliable differences seen between high- and low-risk children from the same high- and low-density families, when evaluated with the same auditory tasks.

Sources of P300 attenuation after head injury: Single‐trial amplitude, latency jitter, and EEG power

Single trial amplitude, latency jitter, and electroencephalographic (EEG) power were examined as sources of the group difference in averaged P300 amplitude among 15 traumatically brain injured and 20 control individuals in an auditory oddball paradigm. Mean amplitude of the individual trials was highly correlated with the amplitude of the averaged P300, with little additional unique variance attributable to latency jitter or EEG power. The group difference in P300 amplitude was also explained by the mean amplitude of the single trials. These results support the robustness of the evtent-related potential averaging technique within the paradigm used.

Auditory and visual P300 event related potentials are not altered in medically and psychiatrically normal chronic marihuana users

Attempts to use Event Related Potentials, particularly the cognitive or P300 evoked potential, as measures of CNS effects of THC use have been infrequent and have produced inconsistent results. We published a pilot study in which psychiatric patient THC users had significantly prolonged auditory P300 latencies and reduced amplitudes as contrasted with non-users. Because psychiatric diagnoses and medication effects could not be controlled, we repeated the study with medically and psychiatrically normal subjects selected with extremely stringent exclusion criteria and screening procedures. P300 latency differences between THC users and controls were not detected. Using all subjects, THC users displayed reduced auditory and visual P300 amplitudes. However, when age differences between THC users and controls were removed, all significant P300 amplitude differences were removed as well. The contaminating effect of using psychiatric patients in THC research is discussed and the importance of using carefully screened normal subjects in studies of neurophysiological abuse drug effects is stressed.

Prolonged P300 latency in a neuropsychiatric population with the D2 dopamine receptor A1 allele.

The role of the dopaminergic system in P300 has been implicated and previous studies have suggested the presence of a heritable component in the genesis of P300 or P3, a late positive component of the event-related potential. In the present investigation, 155 Caucasian male and female diagnosed neuropsychiatrically-ill patients with and without comorbid drug and alcohol abuse/dependence were genotyped for the presence or absence of the A1 allele of the D2 dopamine receptor gene (DRD2). The relationship of the A1 and A2 alleles to P3 amplitude and latency was also determined. The results showed no significant difference in P3 amplitude between all groups studied with A1 and A2 allele carriers. However, we now report prolonged P3 latency in neuropsychiatrically-ill patients (with or without polysubstance abuse) with those carrying two copies of the A1 allele (homozygote) of the DRD2 gene (quadratic trend, p = 0.01). Moreover, the age-adjusted mean P3 latency in the D2A2/A2 allele group was 327.8 +/- 3.08 ms compared by ANOVA, to 360.04 +/- 4.86 ms in the D2A1/A1 group. Our work suggests an association of polymorphisms of the DRD2 gene and a biological marker previously indicated to have predictive value in vulnerability to substance abuse.

Visual P300: An interlaboratory consistency study

The P300 component of the event-related potential is reduced in both abstinent alcoholics and in males at high risk for developing alcoholism. Here, 96 males ( X = 22.1 years ) who were part of an interlaboratory ( n = 6) consistency study in the national COGA (Collaborative Study on the Genetics of Alcoholism) Project were subjects in a visual target selection paradigm. Each of the participating laboratories used the same experimental design, hardware and software, Each subject received a randomized series of target, nontarget and novel visual stimuli, and upon detecting the target stimulus, was required to make a button press as quickly as possible. Statistical analyses indicated that there were no significant differences in P300 amplitude and latency at the Pz electrode under any of the aforementioned conditions across laboratories. Thus, the interlaboratory consistency of the visual P300 indicates that it may be of utility in a national collaborative study on the genetics of alcoholism.

Dynamics of cognitive brain dysfunction in patients with cirrhotic liver disease: an event-related P300 potential perspective

The dynamics of cognitive brain functions of 104 patients with both chronic non-cirrhotic (NC) and cirrhotic liver disease (C: C1, non-encephalophatic; C2, encephalopathic) were investigated by means of visual P300 potentials elicited in both the paradigms of transient (PI) and selective attention (PII). Conventional PVEPs, psychometric tests and quantitative liver function tests were also performed. As compared to both an age-matched control group (N) and the non-cirrhotic patients (NC), the N250 and P300 latencies of the cirrhotics (C) were equally prolonged in both P300 paradigms ( P = 0.0001). By contrast, the P300 amplitudes were not different between the patient groups in either P300 paradigm. In the cirrhotics, however, the P300 amplitude differences between PII and PI (+ 3.7 ± 2.8 μV, mean ± 1 S.D.) were significantly ( P < 0.01) smaller than in the non-cirrhotics (+ 7.5 ± 5.2 μV) lecting disturbances in the dynamics of visual attention. Interestingly, these P300 amplitude differences between both paradigms were positively correlated ( r = 0.35; P = 0.005) with hepatic metabolic capacity, but not with liver blood flow ( r = 0.23; P > 0.05). The diagnostic efficacy of the visual P300 in PI (sensitivity, 48%; specificity, 100%) was lower than that of the visual P300 in PII (79%; 100%) and that of the psychometric tests (63%; 94%), but it remained superior to that of the PVEPs (29%; 97%). It is concluded that in patients with cirrhotic liver disease visual P300 potentials can even reveal the dynamics of minor cognitive brain dysfunction and may also provide interesting pathophysiological information.

P300 differences between non-alcoholic young men at average and above-average risk for alcoholism: Effects of distraction and task modality

1. P300 event-related electroencephalographic potentials were recorded from 79 young adult males, cross-classified with respect to the presence/absence of a family history of alcoholism (FHA) and the presence/absence of a personal history of antisocial personality (ASP) disorder. P300s were elicited using visual and auditory oddball tasks. Each oddball task was repeated with a tracking task added as a distractor. 2. In general, distraction increased the latencies and reduced the amplitudes of P300s elicited by the oddball stimuli. The P300 latency increase occurred only in low risk ASP- and FHA- groups. There was no adaptive increase in P300 latency in the higher risk ASP+ and FHA+ groups. 3. Group differences in P300 were restricted to visual tasks. No interpretable group differences in P300 latency or amplitude were found during the auditory tasks.

P300 from amnesic patients with bilateral hippocampal lesions

P3(00) event-related brain potentials (ERPs) were recorded using auditory and visual stimuli from 5 amnesic patients with confirmed (n = 4) or suspected (n = 1) bilateral damage to the hippocampal formation without skull defects. Four normal control subjects were matched to each amnesic patient with respect to age, sex, education, and IQ subtest scores (n = 20 total controls). All 5 amnesic patients exhibited ERPs, and no reliable differences in P3 amplitude or latency could be detected between the patients and the control subjects in either modality. The findings indicate that the hippocampal formation does not contribute significantly to the scalp-recorded P3 from auditory and visual target stimuli, a conclusion also supported by additional recent findings from studies of patients with extensive bilateral medial temporal lobe damage studies. The significance of the P3 component for cognitive processing is discussed.

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 starting 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.

Somatosensory event-related potentials to painful and non-painful stimuli: effects of attention

In order to determine the effects of attention and distraction on painful and non-painful stimuli, the amplitude changes of 3 components (N150, P200, P300) of the Somatosensory event-related potential (SERF) elicited by painful and non-painful electrical stimuli were investigated. Painful and non-painful stimuli were determined using a visual analog scale. SERPs were recorded from 16 healthy volunteers at 5 midline and 4 left and 4 right hemispheric sites. The differences between the amplitudes of attended and ignored stimuli were quantified with a baseline-to-peak measure. ANOVA results revealed no significant attention or stimulus intensity effects for N150 but highly significant differences in P200 and P300 amplitudes between attended and ignored stimuli. In addition, P200 and P300 amplitudes were larger for strong stimuli than for weak stimuli, with no significant differences between non-painful and painful stimuli. These findings are consistent with the existence of a relative, rather than an absolute, relationship between SERP component amplitudes and subjective pain reports. Furthermore, the data give evidence that attentional manipulations represent a powerful method to decrease the perception of pain and that, when used with subjective and behavioral measures, the SERP represents a valuable asset in the multidimensional approach to pain measurement and assessment.

P300 abnormality in schizophrenic subtypes

P300 and other long latency event-related potentials were recorded in 65 schizophrenic subjects and results were compared to findings in 119 healthy controls. Highly significant differences in P300 latency and amplitude were found between the two groups. Forty six per cent of schizophrenics had P300 latency more than two standard deviations longer than the mean for controls, 35% had a P300 amplitude smaller than the mean for controls by the same amount, and 24% were more than two standard deviations outside the mean for controls on both measures. These differences were independent of chronicity of illness, clinical subtype, family psychiatric history or the effects of neuroleptic medication. They confirm that P300 abnormality is present as a stable trait in a high proportion of schizophrenics. The status of abnormal P300 as a biological vulnerability factor for major mental illness is discussed.

Reduced P3 amplitude of the event-related brain potential: its relationship to language ability in autism.

Several studies have found that P3 amplitude of the auditory event-related potential is smaller in autistic than in normal children. The present study investigated whether this characteristic bears any relationship to the degree of language impairment and/or level of intellectual ability of autistic persons. Seventeen autistic children, ranging from 8-19 years of age, and 17 age- and gender-matched normal children participated. Event-related potentials to phonetic ("Da") and chord (piano) stimuli were recorded from three scalp locations: vertex (Cz), right hemisphere (RH), and left hemisphere (LH), during a discrimination task. A battery of language tests was given to autistic children. Compared to normal subjects, autistic subjects showed a significantly smaller P3 amplitude to phonetic stimuli for Cz and LH recording sites. However, no group difference in P3 amplitude to the phonetic stimulus was found for the RH. Furthermore, no group differences in P3 amplitude were found for the chord stimulus at any recording site. Impaired language ability was related to greater RH P3 amplitude, particularly to the chord stimulus. The possibility of differential hemispheric involvement in the attentional deficits of autistic children is raised.

P300 and the risk for alcoholism: family history, task difficulty, and gender.

P300 event-related brain potentials (ERPs) were obtained from 20 pairs of male and 20 pairs of female undergraduate subjects. One member of each pair reported having a father who was alcoholic (FHP), the other reported no known alcoholic biological relative (FHN). Pair members were matched on age, height, weight, grade point average, and personal drinking history. Three auditory tasks which differed in stimulus discrimination difficulty were presented to each subject. All tasks employed 20% target and 80% standard tones with the subject required to move their index finger whenever a target stimulus was detected. No significant differences in P300 amplitude or latency were obtained between the family history subject groups, although female FHP subjects tended to have smaller P300 amplitudes than their FHN counterparts. P300 amplitude decreased with increases in the amount of self-reported alcohol consumed for FHP subjects but significantly so only for the most difficult task situation. The results suggest that the relationship between the P300 ERP and the inheritability of alcoholism is not yet clear and may be subject to modulation by task requirements, population differences, and subject sex.

Visual evoked potentials in a patient with prosopagnosia

Visual evoked potentials (VEPs) were recorded from a 53-year-old man with prosopagnosia during presentation of slides of known and unknown faces and under two control conditions. ANOVA comparisons with a normal male group showed no differences in P100 amplitude, P300 amplitude or P300 latency. There were no significant evoked potential differences between the patient and controls specifically related to the face conditions. There was, however, a significant delay in the latency of P100 from both hemispheres during all types of stimuli. This prolonged latency was asymmetrical, showing a right sided emphasis with the control conditions: pattern reversal and slides of geometric designs. This finding, of a dissociation in the interhemispheric delay, provides physiological evidence of stimulus-specific organisation at an early, sensory level. The fact that the P100 component showed a marked delay, yet P300 fell within normal limits for amplitude and latency, suggests that this patient's problem lies at a perceptual level.

P300 from normals and adult children of alcoholics

The P300 event-related brain potential (ERP) was obtained from 24 pairs of undergraduate male subjects. One member of each pair reported having a father who was alcoholic (FH+), the other reported no alcoholic family member (FH−). Pairs were matched on height, weight, academic performance, and personal drinking history. Three auditory task situations were employed which manipulated stimulus discrimation difficulty. All tasks employed 20% target and 80% standard tones randomly presented with the subjects required to move their index finger whenever a target tone was detected. No differences in P300 amplitude or latency were obtained between the groups. FH+ subjects tended to demonstrate decreased amplitudes with increased amounts of reported alcohol consumption but only for the most difficult task. The results of the present study suggest that the relationship between the P300 and the heritability for alcoholism is not yet clear and may be modulated by differences in task requirements, subject populations, and personal drinking history.

Cognitive event-related brain potentials in children with attention and reading deficits.

ABSTRACTERPs were recorded from four groups of children: reading disabled, attentional deficit disorder with and without hyperactivity, and normal controls. Subjects pressed a button to a low probability nonsense syllable (target, p= .168) and ignored all other events, which included a high probability nonsense syllable (nontarget, p= .664) and either low probability (category, p= .168) symbols (Block 1) or 3‐letter words (Block 2). The amplitudes of several late ERP components and the latency of the P3 component were examined. The overall amplitude of P3 was significantly smaller in all clinical groups than in controls, but the difference in P3 amplitude between targets and nontargets was smaller only in the two attentional deficit groups. Reading disabled children had smaller P3 and Pc components to words than to symbols, while controls had equivalent values. The N2 component had a different scalp distribution for words and symbols, but did not differentiate reading disabled children from controls. P3 latency was significantly longer in the three clinical groups than in controls, but only the attentional deficit groups showed an increase in P3 latency across blocks of the task. The results are discussed within the framework of recent cognitive models dealing with attentional processes.

Age effects on heart rate, sustained potential, and P3 responses during reaction-time tasks

—Relationships between physiological responses and slowed reaction time (RT) among elderly subjects were tested in 48 healthy young, middle-aged, and elderly men (mean ages 24, 45, and 71 years) using signaled simple and choice RT tasks. There were age reductions in P3 amplitude and heart rate (HR) deceleration, but no effects of age on P3 latency. Sustained potential (SP or CNV) amplitude paradoxically increased with age, possibly indicating weaker inhibitory function. P3 amplitude, SP amplitude, and HR deceleration were most strongly correlated with RT among younger subjects, but SP amplitude was correlated with RT in the elderly group during the choice task. HR deceleration shared a small amount of variance with SP amplitude and RT in the young group. There was no HR-SP-RT relationship in the older groups. Choice-simple task differences in P3 amplitude and RT were correlated in the young and elderly groups. The results suggest that HR, SP, and P3 responses may reflect physiological processes related to the slower RTs of healthy elderly subjects.

P3 reduction in auditory evoked potentials of schizophrenics

Fifteen schizophrenics and 15 age-matched controls performed a reaction time (RT) task. A Bernoulli sequence of 85 dB SPL, 50 msec, 800 c/sec ( P = 0.85) and 1200 c/sec ( P = 0.15) tones was presented with an interstimulus interval of 1 sec. Subjects were instructed to press a button quickly upon hearing the 1200 c/sec tone. If a subject failed to respond within 650 msec, a 50 msec white noise burst occurred. In averages synchronized with target tones and computed without respect to RT, P3 was maximal at Pz with a mean latency of 330 msec for both schizophrenics and controls. P3 amplitude at Pz, however, averaged 6 μV in schizophrenics and 14 μV in controls ( P < 0.001). Both mean RT and mean within-subject variance were greater in schizophrenics than controls. Other kinds of averages were computed to investigate the possibility that the amplitude differences were associated with different RTs or with differences in P3 latency variability in underlying trials. Averages of trials associated with short RTs (100–286 msec) had larger P3s than averages associated with long RTs (287–600 msec) ( P < 0.01). Within each RT range, however, schizophrenic P3s were smaller than control P3s. Neither response-synchronized averaging nor adaptive filtering eliminated P3 amplitude differences between groups, indicating that P3 latency variability cannot account for these differences. We hypothesize that the smaller P3s in schizophrenics represent a deficit in reactivity to unexpected stimuli that is compatible with normal RT performance.

P300 and Reaction Time in Schizophrenics and Controls

This chapter discusses P300 and reaction time in schizophrenics and controls. P300 amplitude differences in average evoked potentials can be because of latency variability in the trials that make up the average. Since under some circumstances P300 latency covaries with RT, the greater RT variability of schizophrenics could indicate greater P300 latency variability in their single trials. Response-synchronized averaging, however, did not eliminate P300 amplitude differences between groups. It is still possible that P300 latency is more variable in schizophrenic single trials, but did not covary with RT. However, the adaptive filter, which works independently of RT, also failed to eliminate P300 amplitude differences between groups. Hence, latency variability is unlikely to account for these amplitude differences. Smaller P300 amplitudes for schizophrenics are present in fast response trials in spite of almost identical RT means and S.D.s for the two groups. These RT data would seem to imply that for these trials both groups are equal in expecting the stimuli, paying attention to them and considering them task relevant.