Hibernation effects on memory in European ground squirrels (Spermophilus citellus)

Effects of hibernation on memory were tested in European ground squirrels ( Spermophilus citellus). The animals were trained in summer to successfully accomplish two tasks: a spatial memory task in a maze and an operant task o n a feeding machine. One group hibernated normally, and the other was preve nted from hibernation by maintaining ambient temperature at 22 degreesC. In spring, the same tasks were repeated for both groups and their individual performances compared to the initial training phase. The experimental group s differed significantly in both tasks. The nonhibernating animals had high er levels of retention and needed significantly fewer trials to relearn the tasks than the group that had hibernated. In addition to testing the reten tion of conditioned tasks, social memory was also studied. The ground squir rels were given a social recognition test in spring with one familiar and o ne unfamiliar conspecific. In contrast to the conditioned tasks, social mem ory did not seem to be affected by hibernation. The results indicate negati ve effects of hibernation on the retention of conditioned tasks, which coul d produce important constraints on animals. A potential explanation for thi s memory loss might be changes in neuronal activity which occur during hibe rnation.