LAUSR

HIGHLIGHTSInstrumental and Pavlovian peak timing tasks were used to assess learning of reward identity and timing.Responding for a devalued reward was selectively impaired but temporal control was maintained.Basolateral amygdala lesions undermined this selective reward devaluation effect but not interval timing.The data suggest that different neural systems contribute to reward identity and temporal learning. ABSTRACT Two experiments with Long‐Evans rats examined the potential independence of learning about different features of food reward, namely, “what” reward is to be expected and “when” it will occur. This was examined by investigating the effects of selective reward devaluation upon responding in an instrumental peak timing task in Experiment 1 and by exploring the effects of pre‐training lesions targeting the basolateral amygdala (BLA) upon the selective reward devaluation effect and interval timing in a Pavlovian peak timing task in Experiment 2. In both tasks, two stimuli, each 60s long, signaled that qualitatively distinct rewards (different flavored food pellets) could occur after 20s. Responding on non‐rewarded probe trials displayed the characteristic peak timing function with mean responding gradually increasing and peaking at approximately 20s before more gradually declining thereafter. One of the rewards was then independently paired repeatedly with LiCl injections in order to devalue it whereas the other reward was unpaired with these injections. In a final set of test sessions in which both stimuli were presented without rewards, it was observed that responding was selectively reduced in the presence of the stimulus signaling the devalued reward compared to the stimulus signaling the still valued reward. Moreover, the timing function was mostly unaltered by this devaluation manipulation. Experiment 2 showed that pre‐training BLA lesions abolished this selective reward devaluation effect, but it had no impact on peak timing functions shown by the two stimuli. It appears from these data that learning about “what” and “when” features of reward may entail separate underlying neural systems.