Effects of prepulse intensity, duration, and bandwidth on perceived intensity of startling acoustic stimuli.

Intense abrupt stimuli can elicit a startle reflex; a weak "prepulse" 30-300 ms earlier can reduce both startle and perceived stimulus intensity. Prepulse inhibition (PPI) of startle, an operational measure of sensorimotor gating, is used to understand brain disorders characterized by gating deficits. Compared to startle, PPI of perceived stimulus intensity (PPIPSI) may provide information that is distinct, and easier to acquire and analyze. To develop this experimental measure, we examined PPIPSI under different stimulus conditions. Both PPI and PPIPSI exhibited a non-linear relationship to prepulse intensity, with prepulses 15 dB(A) above background causing maximal inhibition of both measures. A 50 ms broadband noise prepulse produced maximal PPI and PPIPSI, whereas 5 and 20 ms pure tone prepulses produced maximal PPIPSI and PPI, respectively. PPIPSI is a robust, parametrically sensitive and "low tech" measure of sensory gating that may become a valuable tool for understanding the biology of certain mental disorders.