Long-term memory for DRL: a comparison between weanling, adult and senescent rats

Weanling (24-day-old), adult (3- and 7-month-old) and senescent rats (24-month-old) were submitted for 10 days to a DRL 20 seconds schedule, at a pace of 4 sessions a day. After a 3 month interval, the subjects were tested for retention in an identical experimental setting. In training, the median Interresponse-Time (IRT) is directly related to the age of the subjects, whereas response rates are inversely related to it. Age-related differences subside at the end of training. In testing, adult rats improve their efficiency, whereas senescent and particularly former weanling rats do not catch up with training scores. These data are discussed in relationship with developmental variables in the temporal regulation of behavior, collateral activity, contextual and methodological variables in the study of memory.