MEDIAL-SEPTUM LESIONS DO NOT INCREASE THE SUSCEPTIBILITY OF RATS TO RETROACTIVE INTERFERENCE IN A DELAYED MATCHING-TO-SAMPLE TASK

The effect of food delivery in the delay period on performance in a de layed-matching-to-sample task was explored in rats that had either rec eived lesions of the medial septum or had received sham lesions. The d elay-dependent (rate of forgetting) and delay-independent aspects of t ask performance were assessed using a quantitative model fitted to bia s-free measures of accuracy. The results showed that the delivery of f ood in the delay period caused an overall delay-independent decrease i n accuracy, but only when the food was presented at the end of each de lay (as opposed to the beginning of the delay). The extent of this ove rall decrease in accuracy was the same for both groups. However, only the control group displayed an increase in the rate of forgetting foll owing delivery of food in the delay period. Therefore, the present res ults suggest that the increase in rate of forgetting observed followin g medial septal damage is not the result of an increased susceptibilit y to retroactive interference.