AGE-RELATED DIFFERENCES FOR DURATION DISCRIMINATION IN RATS

The effects of age on duration discrimination were analysed with a sym bolic matching-to-sample task, where a compound signal (light and soun d) was presented at each trial for a duration of either 2 or 10 s. Fou r groups of rats (6, 12, 18, and 24 months old) were trained to press one lever if the signal was short and the other if it was long. Result s show that, in comparison with younger rats (6 and 12 months), presen escent and senescent rats (18 and 24 months) were slower to reach the acquisition criterion. However, when the performance criterion was met , no age-related difference was found: the percentages of correct resp onses were equivalent, whatever the duration of the stimulus. These re sults are in accordance with other data, which have often shown that t he cognitive impairment reported in old animals results more from a sl owness to learn than from an incapacity to discriminate between differ ent durations.