Reflex modification in psychosis-prone young adults.

The present study examined modification of the startle reflex in psychosis-prone and normal control subjects, using a continuous pure tone prestimulus (S1) and an intense white noise startle stimulus (S2). Reflex modification conditions consisted of stimulus pairs with onset asynchronies of 60, 120, and 2000 ms with a startle-alone condition as control. Startle was indexed by the eyeblink, which was measured by vertical electro-oculography. Subjects were identified as psychosis-prone by their high scores on the Perceptual Aberration or the Physical Anhedonia scales. Group differences in blink magnitude inhibition were observed between perceptual aberration and control subjects during short stimulus onset asynchronies, with perceptual aberrators showing significantly less inhibition than controls at 120 ms. No differences were evident between anhedonic and control subjects at the two short onset asynchronies nor were there any significant between-group differences when the interval between stimuli was long (2000 ms). These results suggest that subjects with perceptual aberrations may share with schizophrenics and other schizophrenia-spectrum subjects an underdeveloped mechanism which in normal subjects is presumed to operate during preattentive processing and functions to protect sensory information from the interfering effects of subsequent stimuli.