Lesions of the prelimbic prefrontal cortex prevent response conflict produced by action-outcome associations

Rats with prelimbic (PL) cortex lesions were tested on a discrete-trial discrimination where food rewards were used as both discriminative cues and reinforcing outcomes. On incongruent trials, the discriminative cue food differed from the outcome food; on congruent trials they were the same. When cue and outcome foods differ, a conflict is created between the response directly promoted by the food as a cue (mediated by stimulus-response, S-R, associations) and the response indirectly promoted by the food as an outcome (mediated via action-outcome associations). No conflict is produced when cue and outcome foods are the same. Sham-lesioned rats acquired the discrimination more slowly for incongruent trials than for congruent trials, and incongruent trials were more susceptible to disruption by delay. In contrast there was no difference between congruent and incongruent trial types in PL-lesioned animals during acquisition or delay testing. Delays between cue and response had greater overall effects on lesioned than on sham-lesioned animals. These results are consistent with the behaviour of PL-lesioned animals being controlled by S-R associations with no response conflict due to interference from action-outcome associations.