The effect of prolonged stimulus repetition on autonomic response and EEG activity in normal subjects, schizophrenic, and nonschizophrenic patients.

Abstract

ABSTRACTThe effects of prolonged stimulus repetition were studied in 40 schizophrenics, 40 normal controls, and 40 nonschizophrenic patients. 1000‐Hz, 1‐sec tones with 25‐msec rise times were repeated 70 times at 60 or 90 dB while skin conductance (SCR), finger pulse volume (FPV), and EEG were recorded.Consistent with their hyporesponsiveness in the initial orienting response (OR), schizophrenics displayed less increment in responsiveness with prolonged stimulation, whether in terms of the overextinction (OE) criterion adopted here or of Zahn's post‐habituation response‐rate score. Among the schizophrenics, those with relatively higher post‐habituation response rates showed less emotional withdrawal and greater suspiciousness.OE was more frequent in FPV than in SCR, Since the reverse was true for initial ORs, it is unlikely that the greater FPV‐OE simply reflects bias due to normal arrhythmias. The major incidence of OE response occurred within a narrow range of trials, similar in SCR and FPV. OE response in SCR (but not in FPV) was accompanied by renewed alpha blockade. SCR‐OE was not related to initial SCR‐OR activity, but the data were less consistent for FPV‐OE, leaving the initial OR‐OE relationship somewhat ambiguous. OE was not associated with evidence of cortical inhibition. Instead, electrodermal OE was preceded by a heightening of skin conductance level suggesting some (limited) role for arousal state. Differences between OE and initial OR were discussed.