PARAMETERS AFFECTING GAP DETECTION IN THE RAT

The present research used a startle amplitude reduction paradigm to in vestigate the ability of the rat's auditory system to track rapidly ch anging acoustic transients. Specifically examined was the ability of b rief gaps in otherwise continuous noise to reduce the amplitude of a s ubsequently elicited acoustic startle reflex. The duration of the gap, time between gap offset and startle elicitation (the interstimulus in terval or ISI), and rise-fall characteristics of the gap were systemat ically varied. Consistent with previous research, gaps reliably reduce d startle amplitude. Gaps 2 msec long were reliably detected, and a 50 -msec ISI resulted in the greatest amplitude reduction. Gaps presented at short ISIs produced amplitude reduction that followed a different time course than did gaps presented at longer ISIs. These results may reflect differences in the length of time available for the processing of the stimulus and may involve two different processes.