Hierarchical and binary associations compete for behavioral control during instrumental biconditional discrimination.

In two experiments we investigated the role of hierarchical S-(R-O) associations, as opposed to associative alternatives, in solving biconditional discrimination problems in rats. Using lesions of posterior dorsomedial striatum known to attenuate R-O associative learning, and lesions of the dorsolateral striatum that attenuate S-R learning, we found that whereas the lesions affecting R-O learning abolished biconditional discrimination, lesions of dorsolateral striatum did not (Experiment 1). Furthermore, in Experiment 2, we found, using a more challenging discrimination protocol, that dorsolateral striatal lesions actually enhanced biconditional discrimination learning. These results provide evidence that hierarchical S-(R-O) associations influence instrumental discrimination learning and compete with S-R associations for control of performance.