The differences between schizophrenics and healthy subjects in Somatosensory Evoked Potential (SEP) were studied with 174 schizophrenics (98 male and 76 female) and 200 healthy subjects (100 male and 100 female). SEPs evoked by electric stimuli to the right median nerve were recorded through the two derivations (monopolar : C3’→A1+2; bipolar: C3’→Cz), averaging 100 responses, with 1024 msec of analysis time. Individual SEPs were subjected to the component analysis, and the following statistically significant results were obtained.
1. In male schizophrenics, the peak latencies of SEP components were significantly longer in short-latency component, P1 (bipolar), compared with healthy subjects, and shorter in middle-latency component, P2. In female schizophrenics, those were longer in middle-latency components, N2, P3, N3 (monopolar), and N1, P3, N3 (bipolar).
2. The inter-peak amplitudes in schizophrenics of both sexes were significantly larger in middle-latency components without any changes in short-latency components.
3. A few components with significant differences in latencies and inter-peak amplitudes between the subjects taking neuroleptics more than 600 mg, in chlorpromazine equivalent values, or not, as well as between medicated and unmedicated subjects, coincided with those also between the schizophrenics and healthy subjects.
Theses differences in SEPs confirmed in the present study, regardless of schizophrenic subtypes, suggest the dysfunction in somatosensory information processing in schizophrenics, and SEP abnormalities may serve as possible elctrophysiological indices for cognitive dysfunction in schizophrenics
