The effects of prepulse inhibition timing on the startle reflex and reaction time

A loud acoustic stimulus has been shown to provoke a reflexive startle response and accelerate simple reaction times. However, an auditory prepulse presented in advance of a startling stimulus can reduce the effect of the startling stimulus. The current study examined the effect of the timing of the prepulse on startle-induced reaction times and the startle reflex. The task was to perform a 30 degrees arm extension movement in response to a visual "go" stimulus. On selected trials, an auditory prepulse (80 dB) was presented either 100 ms, 500 ms or 1000 ms prior to the "go" signal. In addition, an auditory startling stimulus (124 dB) was presented in conjunction with the "go" signal on some trials. Our results indicated that an auditory prepulse presented 100 ms, and to a lesser extent 500 ms, significantly decreased the amplitude of the startle reflex; however, the reaction time acceleration associated with the startling acoustic stimulus (SAS) was unaffected. The differential effect of the prepulse on the startle reflex and reaction time acceleration confirm different neural pathways for these effects while the differential effect of the prepulse on the control and startle RTs suggest different mechanisms for movement initiation. (c) 2012 Elsevier Ireland Ltd. All rights reserved.