Still at the choice-point: Action selection and initiation in instrumental conditioning

ABSTRACT: Contrary to classic stimulus–response (S-R) theory, recent evidence suggests that, in instrumental conditioning, rats encode the re-lationship between their actions and the specific consequences that these actions produce. It has remained unclear, however, how encoding this relationship acts to control instrumental performance. Although S-R theories were able to give a clear account of how learning translates into performance, the argument that instrumental learning constitutes the acquisition of information of the form “response R leads to outcome O” does not directly imply a particular performance rule or policy; this in-formation can be used both to perform R and to avoid performing R. Recognition of this problem has forced the development of accounts that allow the O and stimuli that predict the O (i.e., S-O) to play a role in the initiation of specific Rs. In recent experiments, we have used a variety of behavioral procedures in an attempt to isolate the processes that con-tribute to instrumental performance, including outcome devaluation, reinstatement, and Pavlovian–instrumental transfer. Our results, par-ticularly from experiments assessing outcome–selective reinstatement, suggest that both “feed-forward ” (O-R) and “feed-back ” (R-O) associa-tions are critical and that although the former appear to be important to response selection, the latter—together with processes that determine outcome value—mediate response initiation. We discuss a conceptual model that integrates these processes and its neural implementation