[Brain evoked potentials in patients with Alzheimer's disease and schizophrenia: a comparative study].

OBJECTIVE: To investigate the differences of visual evoked potentials(VEP) and auditory evoked potentials(AEP) between patients with Alzheimer's disease and schizophrenics. METHODS: Both VEP and AEP were elicited from 39 patients with Alzheimer's disease, 34 aged schizophrenics and 40 normally age-matched subjects. RESULTS: The variability of waveforms of both VEP and AEP became increased within the AD group. The AD patients presented significantly delayed latencies (N2 and P3 of VEP; P1, N1, P2, N2 and P3 of AEP) as compared to the normal controls. The P2 amplitude of VEP of AD patients was 32% lower than that of schizophrenics and 57% lower than that of the controls. The P2 amplitude of AEP of AD patients was 36% lower than that of schizophrenics and 70% lower than that of the controls. Compared with the normal controls, the schizophrenics showed reduced VEP-P2 latency, prolonged N2 and P3 latencies of both VEP and AEP. The P2 amplitudes of VEP and AEP of schizophrenics were decreased by 16% and 20% respectively as compared to the normal controls. CONCLUSION: The variations of VEP and AEP are a referential tool for diagnosing Alzheimer's disease and schizophrenia.