Sensory gating deficit in a subtype of chronic schizophrenic patients.

The dual click P50 paradigm has been established as a neurophysiological method to detect gating mechanisms. Studies of schizophrenic patients have shown that an insufficient reduction of the P50 amplitude after the second relative to the first stimulus indicates a deficient sensory gating mechanism. The aim of this study was to compare the P50 responses in the dual click paradigm of healthy volunteers to those of patients with different psychotic disorders, especially with regard to psychopathology and nosology according to ICD-10 and DSM-IV and to the classification system of Leonhard. A total of 34 patients and 12 healthy volunteers were investigated electrophysiologically while they performed the P50 dual click experiment. Patients with prominent negative symptoms and without perceptual abnormalities and patients with a hebephrenic subtype of schizophrenia showed less suppression in the dual click P50 paradigm than did healthy controls. Patients with brief/acute and transient psychotic disorders or cycloid psychoses did not differ from healthy volunteers with regard to suppression in the dual click P50 paradigm. No striking influence of gender, age, duration of disease and present medication was found. The findings confirm the lack of sensory gating measured by the dual click P50 paradigms in some but not all patients with schizophrenia. Both subtype of schizophrenia and current form of psychopathology appear to be related to the presence or absence of abnormal sensory gating.