Appetitive odor-cue conditioning attenuates the acoustic startle response in rats.

We here show that a neutral odor previously paired with a positive emotional context is an effective stimulus for attenuating the acoustic startle response (ASR) in rats. Olfactory cues can, therefore, be effectively used in the startle probe procedure for appetitive conditioning. This cue-induced reduction in ASR is not related to attentional alterations or a more general arousal by odor presentation, the conditioned olfactory cue rather elicits a pleasant emotional state during which the ASR is inhibited. This odor conditioned "pleasure" attenuation of the startle response might, therefore, provide a new effective operational measure for the hedonic aspects of reward.