THE ORIENTING RESPONSE TO BRIEF AUDITORY-STIMULI IN PREWEANLING AND ADULT-RATS

The cardiac orienting response to brief auditory stimuli was measured in preweanling and adult rats. The eliciting stimulus varied in durati on (2 or 10 s) and complexity (continuous or pulsing). Stimulus comple xity affected response magnitude with the pulsing stimulus eliciting a larger response than the continuous stimulus. Stimulus duration affec ted response persistence but only when a pulsing stimulus was used. In contrast to recent research with stimuli of much longer duration, age did not significantly affect any aspect of the cardiac response to th e novel auditory stimuli in the present study. These results are discu ssed in terms of (1) the effects of stimulus duration on the heart-rat e component of the orienting response and (2) two-stage models of atte ntion. (C) 1994 John Wiley & Sons, Inc.