Correlations between standard auditory evoked potentials and symptomatology in a group of 50 schizophrenic patients

Standard auditory evoked potentials (AEP) were recorded in 50 schizophrenic patients and 47 normal controls. All patients were rated on the Brief Psychiatric Rating Scale (BPRS), the Scale for the Assessment of Negative Symptoms (SANS), the Scale for the Assessment of Positive Symptoms (SAPS), and the Positive and Negative Syndrome Scale (PANSS), and were classified in three groups (positive-type [n = 10], negative-type [n = 23]and mixed-type [n = 17]patients) according to the normative criteria suggested by Kay. The mean latencies of AEP components (N1, P2, N2) and mean peak-to-peak amplitudes (N1P2, P2N2) did not correlate with age, duration of illness, length of hospitalisation or neuroleptic dosage. The evoked response did not differ between the three groups of patients (positive, negative and mixed). There was only a trend (P = 0.075) to a longer N1 latency in the negative-type group and a shorter one in the positive-type group than in the mixed-type and the control groups. The latency of N1 component correlated significantly with negative symptoms of schizophrenia (SANS scores). This correlation was related to the severity of a depressive dimension of the disorder reflected by the "depressive factor" of BPRS or "affective flattening" and "avolition" subscales of SANS.