VISIBLE PERSISTENCE DECAY-RATES FOR SCHIZOPHRENICS AND SUBSTANCE-ABUSERS

Information-processing deficits are consistently reported for schizoph renics. The findings from the majority of psychophysical tasks indicat e that the deficit is specific to schizophrenics and thus may represen t a marker for schizophrenia. The present study evaluated for specific ity of impairment by including controls using methadone. A two-pulse f orced choice information processing task that required the detection o f a line or a blank-field during an interstimulus interval (ISIJ index ed efficiency of processing (i.e., visible persistence). There were 19 schizophrenic, 9 schizoaffective, 8 depressed, 12 on methadone, and 1 2 normal subjects. The visual stimuli were low and high spatial freque ncy gratings. Either a line of equivalent width to those of the gratin gs or a blank field was presented during the ISI. The gratings were pr esented for 150 msec prior to and following an ISI of 30, 60, 90, 120, 150, and 350 msec. The results support previous findings for impaired processing during a 90-150 msec interval for schizophrenics. Also, th e methadone-using controls were not significantly different from schiz ophrenics. Normal and depressed controls' profiles did not differ from each other, however, they were significantly different from the other groups. The results support an early information-processing deficit i n schizophrenic individuals and may implicate dysregulation of dopamin ergic neuromodulation.