Topography of sensory evoked potentials in depressive disorders

This study investigated differences in evoked potential (EP) topography between psychotic depressives, nonpatient controls, chronic schizophrenics, and neurotic depressives. Somatosensory (SEP), visual, and auditory EPs were recorded from 14 scalp leads. Locations (latencies) of consecutive EP peaks in a given subject were identified visually in key leads; these latencies were used for computer measurements of amplitude in all leads. Four sets of age- and sex-matched groups were compared by multivariate profile analysis. Amplitude differences between groups agreed well with findings obtained by comparing group sum EPs, indicating convergence between the two measurement methods. Topographic differences involved mainly SEP peaks. Distributions of SEP peaks P90 (positivity at 90 msec), N130, and P290 showed more posterior maxima in psychotic depressives than controls, while P185 was maximal more anteriorly in depressives. Distribution of SEP peaks N20, N60, N130, and P185 differed between psychotic depressives and chronic schizophrenics. The topographic approach appears to provide new EP information of pyschiatric relevance.