Enhanced prepulse inhibition of startle using salient prepulses in rats.

Prepulse inhibition (PPI) of the startle reflex occurs when a non-startling stimulus is presented shortly prior to the startling stimulus. PPI is an operational measure for sensorimotor gating. PPI in humans is enhanced by attention, but there is no evidence yet for attentional modulation of PPI in animals. We here combined PPI and conditioned inhibition paradigms in order to investigate attentional modulation of PPI in rats. PPI was assessed before and after training for conditioned inhibition of fear with the conditioned stimulus (auditory CS) and conditioned inhibitor (visual CI) as prepulses. The CI significantly enhanced PPI after training, whereas presentation of the CS had no effect on PPI. These data suggest attentional modulation of PPI in rats by biologically salient prestimuli. This new paradigm may be useful for examining attentional modulation of PPI in animals and to compare attentional modulation in humans and animals.