Effects of discrete acoustic prestimuli on perceived intensity and behavioral responses to startling acoustic and tactile stimuli

Abstract

Startle magnitude is reduced when a startling stimulus is preceded 30–500 msec by a weak prepulse. Although the neurobiology of prepulse inhibition (PPI) of the startle reflex has been studied across species, relatively little is known about the relationship between reduced PPI and information-processing abnormalities in specific neuropsychiatric disorders. In one conceptual model of PPI, the reduced responsivity to sensory events after a prepulse protects the information contained in the prepulse, so that it can be processed adequately. Thus deficient PPI might reflect reduced information-protective abilities and contribute to cognitive dysfunction. Nevertheless, there is little concrete evidence to support this conceptual model. In the present experiment, the relationship of PPI and perceived stimulus intensity was investigated, using both unimodal and cross-modal stimuli to elicit startle and PPI in nonpsychiatric human subjects. The subjects rated the intensity of a startle stimulus presented alone or 60 msec after the onset of an acoustic prepulse versus the intensity of an identical startle stimulus alone, presented 5 sec earlier or later. A negative relationship was observed between the amount of PPI produced by a range of weak-to-intense acoustic prepulses and the perceived intensity of either acoustic or tactile startle stimuli. These findings support an information-protective model for the impact of weak prestimuli on perceived startle stimulus intensity and suggest that deficient PPI in neuropsychiatric disorders may be accompanied by a reduced ability to automatically inhibit, or gate, sensory information.