ABSTRACT
A recent study from our laboratory has provided evidence for the generation of slow potentials occurring in anticipation to task-performance feedback stimuli, in multiple association cortical areas, consistently including two prefrontal areas. In the present study, we intended to determine whether these slow potentials would indicate some abnormality (topographic) in schizophrenic patients, and thus serve as an indication of abnormal association cortex activity. We recorded slow potentials while subjects performed a paired-associates memory task. A 123-channel EEG montage and common average reference were used for 20 unmedicated schizophrenic (mean duration of illness: 11.3 ± 9.2 years; mean number of previous hospitalizations: 1.2 ± 1.9) and 22 healthy control subjects during a visual paired-associates matching task. For the topographic analysis, we used a simple index of individual topographic deviation from normality, corrected for absolute potential intensities. Slow potentials were observed in all subjects. Control subjects showed a simple spatial pattern of voltage extrema (left central positive and right prefrontal negative), whereas schizophrenic patients presented a more complex, fragmented pattern. Topographic deviation was significantly different between groups (P < 0.001). The increased topographic complexity in schizophrenics could be visualized in grand averages computed across subjects. Increased topographic complexity could also be seen when grand averages were computed for subgroups of patients assembled either according to task-performance (high versus low) or by their scores on psychopathological scales. There was no significant correlation between topographic deviation and psychopathology scores. We conclude that the slow potential topographic abnormalities of schizophrenia indicate an abnormality in the configuration of large-scale electrical activity in association cortices.
Subject(s)
Humans , Male , Female , Cerebral Cortex , Evoked Potentials , Schizophrenia , Brain Mapping , Brief Psychiatric Rating Scale , Case-Control Studies , Multivariate Analysis , Photic StimulationABSTRACT
1. We determined the temporal stability of the N1 and P2 waves of the auditory evoked potentials (AEP) for twelve healthy subjects who were tested in two sessions separated by 2 to 63 days (mean = 25 days). AEP were obtained at two different stimulation rates (1/s and 0.3/s). In addition to wave amplitude and latency, the latency difference and the amplitude ratio between the two stimulation rates were calculated. 2. Mean amplitudes, latencies, latency differences and amplitude ratios were not significantly different between the two sessions. Pearson's correlation was significant only for N1 latency at the 1/s stimulation rate (r = 0.64, P = 0.02). 3. Factors such as arousal and other subjective states of the subjects, personality traits, as well as technical aspects of the examinations, may have influenced the temporal stability of the AEP
Subject(s)
Humans , Male , Female , Adult , Acoustic Stimulation , Evoked Potentials, Auditory/physiology , Electroencephalography , Multivariate AnalysisABSTRACT
Varias doencas com importante componente autoimune e com frequente ocorrencia familiar mostraram uma correlacao estatisticamente significante com determidados antigenos de histocompatibilidade (HLA = human leucocyte antigens). Esta correlacao tambem foi encontrada entre HLA e algumas doencas psiquiatricas. No entanto, os resultados de diversos autores tem sido contraditorios. No presente estudo, as frequencias de 31 HLA foram investigadas em 100 pacientes esquizofrenicos e em 472 controles da populacao alema. A frequencia do HLA-B27 estava significativamente aumentada no grupo total de pacientes e nos subgrupos de pacientes paranoides, cronicos, de prgnostico desfavoravel e em pacientes com adoecimento precoce. Nestes ultimos tres grupos encontrou-se tambem um aumento na frequencia do HLA-A9. A combinacao A9-B27 foi dectada em 0,63% dos controles e em 7% dos pacientes. Destes pacientes 85,7% eram esquizofrenicos paranoides cronicos com caracteristicas prognosticas desfavoraveis. Este estudo suporta a possibilidade do uso da tipagem dos antigenos de histocompatibilidade em estudos geneticos das esquizofrenias, assim como no estabelecimente do dignostico diferencial e do prgnostico. Por outro lado, apesar de nossos resultados serem assegurados estatiscamente, o fato de as associacoes estarem bem abaixo de 1,0 indica que outros fatores (presumivelmente ambientais) necessitam estar em jogo na etiologia da doenca