NEUROPHYSIOLOGICAL EVIDENCE FOR A DEFECT IN INHIBITORY PATHWAYS IN SCHIZOPHRENIA - COMPARISON OF MEDICATED AND DRUG-FREE PATIENTS

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  • 1 January 1983
    • journal article
    • research article
    • Vol. 18  (5) , 537-551
Abstract
CNS inhibitory neuronal mechanisms were assessed in clinically stable chronic schizophrenic patients treated with neuroleptic drugs to provide data for comparison with those obtained previously from acutely psychotic, unmedicated patients. An early positive component of the auditory average evoked response recorded at the vertex 50 ms after a click stimulus (P50) was studied. After stimuli were delivered at 10-s intervals to establish a baseline response, inhibitory mechanisms were assessed in a conditioning-testing paradigm by measuring the change in response to a 2nd stimulus following the 1st at either 0.5, 1.0- or 2.0-s intervals. At the 0.5-s interval, normal controls had over an 80% mean decrement in response, whereas schizophrenics showed a mean decrement of less than 10%; however, there was no significant difference in suppression between medicated and unmedicated patients. The amplitude of P50, which was smaller in unmedicated schizophrenics than in normal subjects, was significantly increased in the medicated patients. Inhibitory mechanisms which are dysfunctional in acutely psychotic, unmedicated schizophrenics are not improved by treatment with neuroleptic drugs. Other aspects of sensory neuronal function may be altered by the medication, however, as reflected by the increase in amplitude of P50.