THE EFFECTS OF MAMMILLARY BODY LESIONS ON DELAYED MATCHING AND DELAYED NONMATCHING TO PLACE TASKS IN THE MICE

This study was designed to investigate the effects of different recognition procedures on memory performance in Balb/c mice. To this end, mice were submitted to spontaneous or contingently reinforced delayed non-matching (DNMTP) and delayed matching (DMTP) to place tasks in a T-maze. Results indicate that mammillary bodies (MM)-lesioned subjects are significantly impaired in the DNMTP tasks at the long (6 h) but not the short (5 min) delays; in contrast, they did not exhibit deficits in the DMTP task, whatever the delay considered. We stress the importance of task difficulty as a major factor explaining the different effects of the lesion in the two tasks.