Appetitive learning by old mice.
Groups of C57BL/6J (B6) and DBA/2J (D2) mice, aged 100 to 700 days, were trained on 7 appetitive learning tasks in order to determine which tasks might be suitable for studies of learning by old mice. Old B6 and D2 mice were both deficient in learning a discrimination reversal and two complex maze tasks; age did not affect performance on a simple spatial discrimination by subjects from either strain. Three tasks yielded strain-specific results. Old B6, but not old D2, animals were impaired on a visual discrimination problem. On a test of latent learning, old B6 animals were superior to younger mice, but the reverse trend characterized the D2 mice. Older D2 mice were retarded on a food-seeking task; B6 mice of all ages failed this test. The deficits observed in learning by old mice are thus strain- as well as task-specific. However, the deprivation procedures of this experiment resulted in excessive mortality in the oldest groups of mice, indicating that appetitive learning is contraindicated as a method for investigating learning by old mice.