Posttrial corticosterone administration enhances the effects of incentive downshift: exploring the boundaries of this effect.

Posttrial administration of corticosterone was previously shown to enhance consummatory successive negative contrast (cSNC) in rats. The present series of experiments provides additional information that helps determine the boundaries of this effect. Posttrial corticosterone administration (1) enhances cSNC when rats experience a large downshift (32% to 4% sucrose), but not after a small downshift (8% to 4% sucrose; Experiment 1); (2) has no effect in an anticipatory negative contrast situation in which 4% sucrose precedes 32% sucrose in daily trials (Experiment 2); (3) does not support the development of a conditioned taste aversion to 4% sucrose, in the absence of an incentive downshift (Experiment 3); and (4) facilitates the extinction of consummatory behavior (Experiment 4). These results suggest that corticosterone facilitates the encoding of an egocentric aversive memory of the incentive downshift experience.