Effects of aging upon recent memory in Microcebus murinus.

Four young (2 to 4-year-old) and four aged (9 to 10-year-old) grey mouse lemurs (Microcebus murinus) were given a simple visual discrimination task, and a delayed response visual discrimination task with variable retention delay. The response to the test is a motor one, that consists of choosing one out of four corridors of an apparatus based upon the degree of illumination. The aged animals did not show any learning deficiency, and were capable of memorizing the task for several months. However, they were more sensitive to the length of the delay in the delayed response task than the young animals. It is, therefore, possible to argue that the memory for recent stimulus events is affected during aging. These results corroborate those obtained in other primates, and demonstrate the usefulness of the grey mouse lemur as a new animal model for analyzing aging.