Distributions of the Nd and P300 in a normal sample

Gender effects on auditory P300: A systematic review

The evidence suggests that gender-related effects could influence the electrophysiological P300 parameters and stand as an additional source of variation for both clinical and non-clinical subjects. The aim of this paper is to characterize gender-related differences in P300 potential as elicited with simple auditory paradigms. This knowledge (1) is important for the practical assessment of P300 potential in normal and clinical populations, and (2) can provide an insight into the understanding of gender differences in pathophysiology, particularly those with differential risk or prevalence in males and females. With this review it is shown that a limited number of studies encounter possible gender effects on parameters of auditory P300, and the findings need to be read with caution due to methodological limitations of the studies. Nevertheless, evidence supports that the P300 amplitude could be significantly modulated by gender, with greater amplitude in females relative to males. Noteworthy, gender has a minimal effect on the P300 latency, and it is often comparable between males and females. Furthermore, the effect of gender on P300 could be modulated by hormonal background, anatomy and some methodological aspects.

Reduction of auditory event-related P300 amplitude in subjects with at-risk mental state for schizophrenia

Neurophysiological methods allow the examination of cognitive-cortical functioning in patients with schizophrenia in its prodromal states. As revealed by previous studies, event-related potential components such as auditory evoked P300 associated with cognitive processes, such as attention and orientation, are known to be reduced in amplitude in acute and chronic as well as in medicated and unmedicated patients. It is, however, unclear whether a P300 amplitude reduction occurs before the schizophrenic psychosis is fully manifested. We studied patients in the prodromal phase of the schizophrenic disorder (i.e. subjects with an at-risk mental state showing attenuated psychotic symptoms or brief limited intermittent symptoms) as well as first-episode patients and chronic patients with schizophrenia and compared these groups to healthy subjects. The event-related P300 was recorded during an auditory oddball paradigm. Groups differed significantly from each other in the P300 amplitude at Pz (F(3/149)=2.532, p=0.02). Post-hoc tests revealed significantly lower P300 amplitudes of non-medicated prodromal (p=.03), first-episode (p=.01) and chronic patients (p=.001) compared to the healthy controls. The study revealed that there are neurophysiological changes as the reduction in P300 amplitudes begins early in schizophrenia at the prodromal phase, i.e. before a manifestation of full-blown psychosis, and that these changes seem to have a progressive course from prodromal to chronic state of schizophrenia as assumed in this cross-sectional study.

Event-related potential correlates of the word length effect in working memory

It has been proposed that a frontally distributed ERP negativity reflects rehearsal within the phonological loop component of working memory. This study investigated the relationship between phonological rehearsal and frontal negativity, by examining the effects of word length and articulatory suppression (continuously uttering an irrelevant word) on memory for auditorily presented words while ERPs were recorded. P2 amplitude, thought to reflect word identification, was increased for long compared to short words. However, this difference did not remain under conditions of suppression. A centrally maximum early negativity was larger in the short than long word silent conditions and this word length effect was reduced under suppression. The early negativity was interpreted as reflecting the transfer of the information from input to output buffers in the silent conditions that was prevented by the suppression. There was only a word length effect for the late frontally distributed negativity in the suppression conditions, suggesting that this component was not associated with phonological loop rehearsal but rather other working memory processes that operate under high load conditions.

Auditory P3 indexes personality traits and cognitive function in healthy men and women

The relationship of the auditory P3 event-related potential to major personality dimensions and neuropsychological performance was examined in psychiatrically healthy men and women (28 male, 15 female) recruited from the community. An auditory oddball paradigm was used to collect P3 amplitude and latency data. Personality traits were measured with the NEO Five-Factor Inventory. Several Wechsler Adult Intelligence Scale-Revised (WAIS-R) subtests, the Digit Symbol Test, and the Trail Making Test comprised the neuropsychological tests. A multivariate statistical procedure (Partial Least Squares) was used to quantify the relationships between P3 variables and personality and neuropsychological performance variables. P3 amplitude was negatively related to Neuroticism and positively related to Extraversion, Openness, Agreeableness and Conscientiousness. Better neuropsychological performance was associated with greater P3 amplitude and earlier latency. Thus, greater P3 amplitude was associated with less deviant personality scores and better neuropsychological performance in healthy subjects. Earlier P3 latency was also associated with better neuropsychological performance. The physiological significance of these relationships is not yet clear, but these results suggest that neural assemblies indexed by P3 may subserve both elemental cognition and healthy personality function.

Residual symptoms and P300 in schizophrenic outpatients

A reduced P300 amplitude has often been found to be related to schizophrenic psychopathology. It is still unclear, however, whether this relationship is trait- or state-dependent. We investigated 88 stabilized schizophrenic outpatients during a 2-year follow-up period. Multivariate analyses revealed that patients who had reduced P300 amplitudes showed pronounced residual symptoms, especially thought disorder (Brief Psychiatric Rating Scale). Intraindividual changes in that psychopathology were not correlated to corresponding changes of the P300 amplitude, so the relationship between schizophrenic psychopathology and P300 amplitude appears to be, at least in part, trait-dependent. A reduced P300 amplitude may characterize a subgroup of schizophrenic patients with a disposition to cognitive disturbances and incomplete remissions.

Auditory event-related potentials to a two-tone discrimination paradigm in attention deficit hyperactivity disorder

Auditory event-related potentials (ERPs) were recorded from 10 children diagnosed with attention deficit hyperactivity disorder (ADHD) and 10 age-, sex-, and IQ-matched control children. ERPs were recorded from 17 electrodes during an auditory two-tone discrimination ("oddball') paradigm. Subjects were instructed to press a hand-held response button to infrequently presented target tones. ERP components elicited to target and non-target stimuli were analyzed for between-group differences. Results indicated that for the children with ADHD relative to control children, an N2 component to non-target stimuli was larger in the posterior region and smaller in the frontal region. The P3b component to target stimuli was smaller in the posterior region and larger in the frontal region for the ADHD group compared with the control group. The between-group differences in P3b scalp distribution are indicative of a between-group difference in the neural generators of P3b. It is proposed that the ADHD group, relative to controls, utilizes an additional cognitive process when processing task-relevant stimuli. This process is more frontally distributed and may reflect an attentional compensation mechanism in the ADHD group.

Meta-analysis of P300 normative aging studies

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

Event-related potential correlates of functional hearing loss: reduced P3 amplitude with preserved N1 and N2 components in a unilateral case

A female patient exhibiting functional hearing loss in her left ear demonstrated reduced amplitude of P3 component in event-related potentials (ERP) to left monaural stimulation, with preserved N1 and N2 components to stimulation of either ear. This result suggested that stimuli in the affected ear were conducted successfully up to the auditory cortex but that further processing in higher brain regions was 'repressed'. Event-related potential examination for such hysterical disorders could be useful in clarifying their brain mechanism and offer a useful diagnostic clue to its nature.