Sensory gating in schizophrenics and normal controls: effects of changing stimulation interval.

Auditory evoked potentials were recorded using a paired click, conditioning-testing paradigm in 10 schizophrenics and in 10 normal subjects with no family history of psychotic disorder. The paradigm is used to demonstrate central nervous system gating of responsiveness to auditory stimuli by examining the extent to which the response to the conditioning stimulus diminishes the response to a test stimulus occurring a short time later. Recordings were made at conditioning-testing intervals of 500 msec, 150 msec, and 75 msec to determine subjects' gating of responsiveness to stimuli repeated at various intervals. The schizophrenics had conditioning-testing ratios indicative of poor gating of the auditory P50 wave at the 500-msec and 150-msec intervals, but most patients had good sensory gating at the 75-msec interval. Normal subjects showed good sensory gating at all three intervals. Results suggest that although sensory gating mechanisms responsible for changes in neuronal response at longer intervals are chronically defective in schizophrenics, other gating mechanisms functioning at shorter intervals appear to be intact and function well in most patients. The results may lead to increased specification of the neurobiological basis of sensory abnormalities in schizophrenia.