Disruption of Free-Operant Successive Discriminations by Septal Damage in Rats

Abstract

In Experiment I rats were trained preoperatively on a successive, free-operant discrimination with fixed component durations until S— responding had been minimized. Septal damage resulted in a transitory loss of discriminative performance due to an elevation of S— responding. Experiment II showed a comparable septal deficit following training which employed a “correction” procedure that penalized S— responding. It is concluded that, even after extended training, the maintenance of a low level of S— responding by rats in these types of discriminations requires the operation of an active mechanism which can be disrupted by septal damage. The possibility that this disruption results from a lesion-induced change either in the primary reactions to frustrative non-reward or in associated processes is discussed.