Latência e amplitude do P300 auditivo na doença de Alzheimer: uma revisão sistemática

O P300 desempenha um papel fundamental como método de avaliação e monitoramento das demências, entre elas a doença de Alzheimer. OBJETIVO: Realizar uma busca por artigos que analisaram os valores de latência e amplitude de P300 na doença de Alzheimer. MÉTODOS: Foi realizada uma busca nas seguintes bases de dados: Web of Science, PubMed/Medline, Psyc Info, Biological Abstracts e Scielo. Utilizaram-se as seguintes palavras-chave: speed of information processing, speed of processing, information processing, aged, older, elderly, older people, alzheimer dementia, alzheimer disease, Alzheimer, além de referências cruzadas dos artigos selecionados. RESULTADOS: Foram encontrados oito estudos que preencheram os critérios de inclusão adotados para o presente trabalho. Estes estudos mostraram que existe um consenso em relação ao aumento da latência de P300 de idosos com doença de Alzheimer quando comparados com idosos sem a doença. Porém, verifica-se que, com relação à amplitude de P300, ainda não há um consenso, mas, isso pode estar relacionado às diferentes variáveis metodológicas adotadas nos estudos revisados. CONCLUSÃO: Há necessidade de se padronizar as variáveis envolvidas no método de avaliação do P300 para idosos com doença de Alzheimer, para que seja possível comparar os valores de latência e amplitude de P300 dessa população.

Síndrome da apneia obstrutiva do sono e o potencial auditivo P300

A Síndrome da Apneia Obstrutiva do Sono (SAOS) diminui as capacidades da atenção, memória e concentração, fatores relacionados com a cognição. A análise dos parâmetros do P300 auditivo permitiria inferir disfunção cognitiva. OBJETIVO: Comparar os dados da polissonografia e do P300 auditivo em adultos, roncopatas primários com portadores de SAOS. CASUÍSTICA E MÉTODO: Estudo prospectivo em roncopatas primários (N=12) e em portadores de SAOS (N=54), submetidos à polissonografia definidos pelo índice de apneia e hipopneia (IAH). As variáveis da polissonografia e as do P300 foram comparadas, pelos testes T de Student, exato de Fisher, regressão logística e análise de correlação com nível de significância de 5%. RESULTADOS: O IAH apresentou correlação inversa com a oximetria em ambos os grupos. A prevalência do P300 foi menor no G.SAOS (teste exato de Fisher, p=0,027). A idade dos pacientes não influenciou a prevalência do P300 (análise de regressão; p=0,232). A amplitude do P300 foi menor do G.SAOS (teste T de Student; p=0,003) a latência do P300 foi semelhante em ambos os grupos (teste T de Student; p=0,89). CONCLUSÃO: A redução da amplitude do P300 nos portadores de SAOS sugere disfunção cognitiva induzida por diminuição da memória auditiva.

The interactive effects of alcohol and temazepam on P300 and reaction time

The present research investigated the separate and interactive effects of the minor tranquilliser, temazepam, and a low dose of alcohol on the amplitude and latency of P300 and on reaction time. Twenty-four participants completed four drug treatments in a repeated measures design. The four drug treatments, organised as a fully repeated 2 x 2 design, included a placebo condition, an alcohol only condition, a temazepam only condition, and an alcohol and temazepam combined condition. Event-related potentials were recorded from midline sites Fz, Cz, and Pz within an oddball paradigm. The results indicated that temazepam, with or without the presence of alcohol, reduced P300 amplitude. Alcohol, on the other hand, with or without the presence of temazepam, affected processing speed and stimulus evaluation as indexed by reaction time and P300 latency. At the low dose levels used in this experiment alcohol and temazepam appear not to interact, which suggests that they affect different aspects of processing in the central nervous system. (C) 2003 Elsevier Inc. All rights reserved.

Genetic sources of covariation among P3(00) and online performance variables in a delayed-response working memory task

Genetic and environmental sources of covariation among the P3(00) and online performance elicited in a delayed-response working memory task, and psychometric IQ assessed by the multidimensional aptitude battery, were examined in an adolescent twin sample. An association between frontal P3 latency and task performance (phenotypic r = -0.33; genotypic r = -0.49) was indicated, with genes (i.e. twin status) accounting for a large part of the covariation ( > 70%). In contrast, genes influencing P3 amplitude mediated only a small part (2%) of the total genetic variation in task performance. While task performance mediated 15% of the total genetic variation in IQ (phenotypic r = 0.22; genotypic r = 0.39) there was no association between P3 latency and IQ or P3 amplitude with IQ. The findings provide some insight into the inter-relationships among psychophysiological, performance and psychometric measures of cognitive ability, and provide support for a levels-of-processing genetic model of cognition where genes act on specific sub-components of cognitive processes.

Effects of caffeine on the electrophysiological, cognitive and motor responses of the central nervous system

Caffeine is the most consumed psychoactive substance in the world. The effects of caffeine have been studied using cognitive and motor measures, quantitative electroencephalography (qEEG) and event-related potentials. However, these methods are not usually employed in combination, a fact that impairs the interpretation of the results. The objective of the present study was to analyze changes in electrophysiological, cognitive and motor variables with the ingestion of caffeine, and to relate central to peripheral responses. For this purpose we recorded event-related potentials and eyes-closed, resting EEG, applied the Stroop test, and measured reaction time. Fifteen volunteers took caffeine (400 mg) or placebo in a randomized, crossover, double-blind design. A significant reduction of alpha absolute power over the entire scalp and of P300 latency at the Fz electrode were observed after caffeine ingestion. These results are consistent with a stimulatory effect of caffeine, although there was no change in the attention (Stroop) test or in reaction time. The qEEG seems to be the most sensitive index of the changes produced by caffeine in the central nervous system since it proved to be capable of detecting changes that were not evident in the tests of cognitive or motor performance.

Increased NoGo-anteriorisation in first-episode schizophrenia patients during Continuous Performance Test

OBJECTIVE: NoGo-stimuli during a Continuous Performance Test (CPT) activate prefrontal brain structures such as the anterior cingulate gyrus and lead to an anteriorisation of the positive electrical field of the NoGo-P300 relative to the Go-P300, so-called NoGo-anteriorisation (NGA). NGA during CPT is regarded as a neurophysiological standard index for cognitive response control. While it is known that patients with chronic schizophrenia exhibit a significant reduction in NGA, it is unclear whether this also occurs in patients undergoing their first-episode. Thus, the aim of the present study was to determine NGA in a group of patients with first-episode schizophrenia by utilizing a CPT paradigm. METHODS: Eighteen patients with first-episode schizophrenia and 18 matched healthy subjects were investigated electrophysiologically during a cued CPT, and the parameters of the Go- and NoGo-P300 were determined using microstate analysis. Low resolution tomography analysis (LORETA) was used for source determination. RESULTS: Due to a more posterior Go- and a more anterior NoGo-centroid, NGA was greater in patients than in healthy controls. LORETA indicated the same sources for both groups after Go-stimuli, but a more anterior source in patients after NoGo-stimuli. In patients P300-amplitude responses to both Go- and NoGo-stimuli were decreased, and P300-latency to NoGo-stimuli was increased. After the Go-stimuli false reactions and reaction times were increased in patients. CONCLUSIONS: Attention was reduced in patients with first-episode schizophrenia, as indicated by more false reactions, prolongation of reaction time, P300-latencies and by a decrease in P300-amplitude. Significantly however, the NGA and prefrontal LORETA-sources indicate intact prefrontal brain structures in first-episode schizophrenia patients. Previously described changes in this indicator of prefrontal function may be related to a progressive decay in chronic schizophrenia. SIGNIFICANCE: The results support the idea of a possible new biological marker of first episode psychosis, which may be a useful parameter for the longitudinal measurement of changing prefrontal brain function in a single schizophrenia patient.

White matter anisotropy related to electrophysiology of first episode schizophrenia during NoGo inhibition

Patients with schizophrenia have reduced execution functions and white matter alterations indicating cerebral disconnectivity. Here we investigated the relationship between white matter integrity and event related potentials (ERP) during a continuous performance test (CPT). Anisotropy values were correlated with the brain electrical P300 microstate duration and P300 latency associated to the NoGo- and the Go-stimuli of the CPT in 11 patients with first episode schizophrenia and 11 matched healthy controls. Both groups showed significant positive correlations of the NoGo-microstate duration with the white matter signal in the superior frontal region, the optic radiation, the posterior cingulate, and the inferolateral fascicle. In addition, patients with first episode schizophrenia had significant correlations with the right radiation and the left genu of the corpus callosum, bilateral geniculate, and the left middle and the superior temporal regions. We interpreted these findings as a sign of functional correlates of extended circuits for the active inhibition of a motor response in the visual CPT as compared to controls.

Attentional blink and impulsiveness: evidence for higher functional impulsivity in non-blinkers compared to blinkers

The attentional blink (AB) represents a fundamental limit of information processing. About 5-10 % of all subjects, however, do not show the AB. Because of the low base rate of these so-called non-blinkers, studies on mechanisms underlying non-blinkers' absent AB are extremely scant. The few existent studies found non-blinkers to be faster and more efficient in information processing compared to blinkers. A personality trait that has been linked previously to speed and efficiency of information processing as well as to the magnitude of the AB is impulsivity. Therefore, the present study investigated whether 15 non-blinkers and 15 blinkers differed from each other in functional and/or dysfunctional impulsivity. To obtain a better understanding of the underlying processing mechanisms, the P300 component in the event-related potential was recorded during performance on the AB task. Our results indicated higher functional impulsivity in non-blinkers compared to blinkers but no differences between the two groups in dysfunctional impulsivity. As indicated by shorter P300 latency, non-blinkers processed information faster than blinkers after the AB period but slower during the AB period. These speed effects, however, were not associated with functional impulsivity. Thus, impulsivity and speed of information processing appear to represent two rather independent sources for non-blinkers' absent AB

Stuttering treatment control using P300 event-related potentials

Positron emission tomography studies during speech have indicated a failure to show the normal activation of auditory cortical areas in stuttering individuals. In the present study, P300 event-related potentials were used to investigate possible effects of behavioral treatment on the pattern of signal amplitude and latency between waves. In order to compare variations in P300 measurements, a control group paired by age and gender to the group of stutterers, was included in the study. Findings suggest that the group of stutterers presented a significant decrease in stuttering severity after the fluency treatment program. Regarding P300 measurements, stutterers and their controls presented results within normal limits in all testing situations and no significant statistical variations between pre and post treatment testing. When comparing individual results between the testing situations, stutterers presented a higher average decrease in wave latency for the right ear following treatment. The results are discussed in light of previous P300 event-related potentials and functional imaging studies with stuttering adults. Educational objectives: The reader will learn about and be able to describe the: (1) use of P300 event-related potentials in the study of stuttering; (2) differences between stuttering and non-stuttering adults; and (3) effects of behavioral fluency treatment on cerebral activity in stuttering speakers. (C) 2011 Elsevier Inc. All rights reserved.

Genetic influence on the variance in P3 amplitude and latency

The P3(00) event-related potential (ERP) component is widely used as a measure of cognitive functioning and provides a sensitive electrophysiological index of the attentional and working memory demands of a task. This study investigated what proportion of the variance in the amplitude and latency of the P3, elicited in a delayed response working memory task, could be attributed to genetic factors. In 335 adolescent twin pairs and 48 siblings, the amplitude and latency of the P3 were examined at frontal, central, and parietal sites. Additive genetic factors accounted for 48% to 61% of the variance in P3 amplitude. Approximately one-third of the genetic variation at frontal sites was mediated by a common genetic factor that also influenced the genetic variation at parietal and central sites. Familial resemblance in P3 latency was due to genetic influence that accounted for 44% to 50% of the variance. Genetic covariance in P3 latency across sites was substantial, with a large part of the variance found at parietal, central, and frontal sites attributed to a common genetic factor. The findings provide further evidence that the P3 is a promising phenotype of neural activity of the brain and has the potential to be used in linkage and association analysis in the search for quantitative trait loci (QTLs) influencing cognition.

Medición del potencial evocado cognitivo, P300, en un grupo de individuos colombianos sanos

Los potenciales evocados cognitivos son mediciones electrofisiológicas relacionadas con procesosque tienen que ver con ciertas funciones cognitivas. El potencial cognitivo P300 está específicamenterelacionado con procesos de atención. Objetivo: identificar valores para la latencia y amplitud deonda P300 en una muestra de individuos colombianos y describir su comportamiento con respectoa edad, género y escolaridad de los sujetos. Método: se estudiaron 122 sujetos sanos entre los 6 y80 años, se practicó medición del potencial según la metodología odd-ball, en las derivaciones Czy Pz. Resultados: se identificaron valores medianos, mínimos y máximos para diferentes gruposetarios y se estableció que la latencia de la onda P300 aumenta con la edad de los individuos yque, por el contrario, la amplitud de la misma tiende a disminuir. De igual forma, al correlacionarlatencia y amplitud, se evidenció una relación inversa. Conclusiones: no se encontraron diferenciaspara latencia y amplitud de onda relacionadas con el género ni la escolaridad de los sujetos, asícomo tampoco se halló diferencia al realizar la medición en la derivación Pz comparada con laonda obtenida en la derivación Cz.

Effects of Transcranial Magnetic Stimulation on the Cognitive Event-Related Potential P300: A Literature Review

The objective of this study was to perform a systematic review regarding the effects of transcranial magnetic stimulation (TMS) on the cognitive event-related potential P300. A search was performed of the PubMed database, using the keywords "transcranial magnetic stimulation" and "P300." Eight articles were selected and, after analysis of references, one additional article was added to the list. We found the comparison among studies to be difficult, as the information regarding the effects of TMS on P300 is both scarce and heterogeneous with respect to the parameters used in TMS stimulation and the elicitation of P300. However, 7 of 9 studies found positive results. New studies need to be carried out in order to understand the contribution of these variables and others to the alteration in the latency and amplitude of the P300 wave.