[Effects of modality on rats' short-term memory in successive matching-to-sample task]

This study examined the effects of modality on rats' short-term memory by using the go/no-go delayed paired stimuli comparison task (Konorski task). Each of paired stimuli (S1, S2) was successively presented in order with delay intervals, and a food pellet was contingent upon the lever pressing only when S2 matched S1 (light; L or tone; T). The accuracy of discrimination between the matched and nonmatched pairs decreased as a function of delay interval. Steeper forgetting was shown when a visual stimulus was presented as S1 (S1-L trials) than when an auditory S1 (S1-T trials) was presented. The longer was the ITI duration, the better was the performance in the S1-T trials, but this was not true for the S1-L trials. Further, discrimination performance was an increasing function of the duration of S1 regardless of the modality of S1. These results were discussed mainly on the basis of interference theory and decay theory of forgetting.