Effects of septal lesion on go, no-go differentiation and reversal learning in rats

Experiments were done on 24 Sprague-Dawley male albino rats. Acquisition of go, no-go differentiation and its reversal were compared between normal and septal animals. Rats were trained in Skinner boxes on a 30-s VI food reinforcement schedule. Differentiation sessions consisted of periods with flashing and steady light on, randomly distributed. In half the subjects of each group reinforcement was available only during the flashing light (CS+ periods) while during the steady light no reinforcement was delivered (CS- periods). For the remaining subjects the allocation of stimuli as CS+ or CS- was reversed. During reversal training the signalling properties of the stimuli were reversed. The experiments confirmed that there is lesion-induced increment in base-line response rate. During differentiation training septal damage had no significant effect on the proportion of total responses emitted during CS-, although it increased the overall rate of CS- responding when the flashing light was used as CS-. During reversal training when the flashing light was used as CS- septal animals both responded at a higher rate during CS-, and emitted a higher proportion of their responses during CS-, relative to controls. There were no lesion effects on CS- responding when the steady light was used as CS-. Thus the septal deficit appeared when the to-be-extinguished habit was fairly strong and only under conditions of greater stimulus generalization. These results indicate that septal effects depend on a variety of experimental factors determining performance in any given test situation, among which stimulus intensity dynamism is one of particular importance.