DRL responding under uncertain reinforcement in rats after medial frontal cortical lesions.

Rats were studied for their performance on DRL 10-s schedule with a 50% probability of reinforcement of a correct response with a food pellet. It was found that the performance of a group of 8 rats with medial frontal decortication by aspiration was deficient compared to a group of 7 sham-operated control rats. The deficit manifested in the form of an increase in very short interresponse times (IRTs). This signifies an influence of medial frontal cortex on the control of responding by time-correlated stimuli probably arising from collateral behaviours.