Skin conductance habituation during acute episodes of schizophrenia: qualitative differences from anxious and depressed patients.

Abstract

Skin conductance habituation was measured in schizophrenic patients (N = 41) during an acute episode and compared with neurotic patients (N = 86) who were either predominantly anxious or predominantly depressed. All patients were tested before the onset of drug treatment. Between the 14th and 15th tone of the 17 tone simple habituation series a loud 'dishabituating' tone was inserted. In terms of traditional measures based on response frequency, non-habituation was most frequent in the anxious patients and least frequent in the depressed patients, with schizophrenic patients being intermediate. However, in terms of response amplitude the schizophrenic patients showed significantly faster habituation than either neurotic group. This paradox seems to be a consequence of the frequency of spontaneous fluctuations which was highly related to habituation status in the schizophrenic group, but not in the neurotic groups. When habituation was defined in terms of response amplitudes falling below spontaneous fluctuation amplitudes (rather than zero) the schizophrenic group showed the lowest frequency of non-habituation. None of the groups showed any evidence of dishabituation after the loud tone, but the schizophrenics showed a significantly smaller response to the loud tone itself. Following Groves & Thompson (1970), this is interpreted as showing that the loud tone induced a greater response because of its perceived difference from the other tones rather than a sensitization effect because of its loudness. In these terms the schizophrenic patients showed greater response generalization than the neurotic patients.