Cerebral Evoked Potentials in Patients at an Early Stage of Schizophrenia

Visual and auditory EPs (with special attention to their cognitive components) were examined in 33 patients with newly diagnosed schizophrenia (a group of patients, Pat; all subjects obtained supporting pharmacotherapy) and 30 mentally healthy subjects (a control group, Contr). Reversive chess patterns with the squares of 60 or 120 ang. sec were used as stimuli in the case of visual EPs, while tones of different frequencies, 1.0 and 4.0 kHz, were used for initiation of auditory EPs. The odd-ball paradigm was used; the probabilities of significant stimuli (i.e., signals) at each sensory modality were 20 or 50%. The amplitudes and latencies of generally differentiated EP components, with special attention to the P1, N1, P2, N2, P3 (P300), and N4 waves, were measured; in addition, the latencies (times) of sensorimotor reactions (SMRs) to presentation of the signal stimuli (pushing the button) were recorded. The averaged latencies of visual N1, P2, N2, P300, and N4 (at the 50% probability) and of N2, P300, and N4 (20% probability) in patients with schizophrenia were significantly longer than those in the control. Besides, the amplitudes of visual P2 and N2 (50% probability) and of P2, P300, and N4 (20% probability) were significantly lower than in the control. At auditory stimulation, the latencies of nearly all EP components in the Pat group at both 50 and 20% probabilities of significant stimuli were longer that in the norm, but the differences did not reach the significance level. The amplitudes of components P1–N2 in auditory EPs at the 50% probability were significantly lower than in the control. Significantly longer latencies (times) of the SMRs were observed in the Pat group at both auditory and visual stimulation and at both probabilities of significant stimuli. It is concluded that the cognitive deficit in patients with schizophrenia is probably more clearly reflected in the parameters of visual EPs, while changes in the positive symptoms of this disease are more reflected in the parameters of auditory EPs.

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