The Relationship of Automatic and Controlled Processing to Prepulse Inhibition

Abstract

Abstract When a weak stimulus, or prepulse, is presented immediately prior to a startle reflex-eliciting stimulus, the startle reflex is inhibited. This is called prepulse inhibition (PPI). Directing attention to a prepulse increases PPI. In two experiments (N = 43 and N = 29), attention was directed to the prepulse by having the participants judge the duration of the prepulse. Prepulse inhibition was assessed at stimulus onset asynchronies (SOAs) assumed to index automatic and controlled processing. The prepulse was a 60dB tone, and startle was elicited by 95dB white noise. We predicted that attention directed to the prepulse should increase PPI, and that PPI should increase on trials with correct judgments of prepulse duration compared to trials with incorrect judgments. The results from both experiments showed that attention directed toward the prepulse increased PPI at SOAs assumed to index both automatic and controlled processing. This indicates that controlled attention exerted an influence on automatic processes. There was no evidence that PPI was increased on trials with correct judgment of prepulse duration. It is concluded that attention to the prepulse increased PPI, but PPI did not differentiate between automatic and controlled processing under the present experimental conditions.