High-frequency changes in single-trial visual evoked potentials for unattended stimuli in chronic schizophrenia.

Background: Patients with schizophrenia reveal changes in information processing associated with external stimuli, which is reflected in the measurements of brain evoked potentials. We discuss actual knowledge on electro- (EEG) and magnetoencephalographic (MEG) changes in schizophrenia.

New Method: The commonly used averaging technique entails the loss of information regarding the generation of evoked responses.

[Distribution of latencies of visual evoked potentials in a sample of schizophrenic patients].

Aim: The aim of the study is an analysis of distribution of visual evoked potentials (VEP) latencies in the group of schizophrenic and healthy subjects.

Method: A study was carried out on a group of 30 patients (8 males and 22 females) with a DSM-III-R diagnosis of schizophrenia (disorganised schizophrenia--5, paranoid schizophrenia--12, residual schizophrenia--6, and undifferentiated schizophrenia--6). During the study 20 patients were given neuroleptics, 10 patients did not receive treatment.

[Brain evoked potential in schizophrenic patients].

The authors reviewed the literature on evoked potentials in mentally ill patients, with particular emphasis on schizphreniacs. The commonly observed abnormalities were as follows: 1) higher SEPs amplitudes with less waveshape variability during first 100 ms in non-depressed chronic, paranoid or undifferentiated patients with florid psychotic symptoms; normal SEPs amplitudes in acute or latent schizophrenics and in chronic depressed schizophrenics but without florid psychotic symptoms; 2) reduced SEPs and VEPs amplitude recovery and faster latency recovery; 3) reduced AEPs amplitude and latency; 4) greater VEPs waveshape variability and tendency to be "reducers" in hallucinating patients; reduced amplitude and latency recovery; prolonged latencies in patients with positive family history (schizophrenia or affective disorders in close relatives); prolonged N2 latency in motor responses to "easy" and "difficult" stimuli; reduced activity of "late potentials"; 5) greater waveshape variability in all modalities in chronic schizophrenics, abnormal P300 (reduced amplitude, lack of P300 or negative "effect of uncertainty") and abnormal CNV (less "readiness" potential, prolonged negativity with motor responses).