Figure 7.

(A) Training and testing on a “naturalistic” odor–odor association. In phase I a “demonstrator” rat is given a distinctively scented food. Then, in phase II, the demonstrator is presented to an experimental subject for a brief period of social interaction. During this experience subjects associate two odors carried on the demonstrator’s breath, the distinctive food odor and carbon disulfide (CS₂), a natural constituent of rats’ breath (ref. 46; phase II). In phase III, to test memory for the food odor–CS₂ association, subjects are presented with the same food or another distinctively scented food, either immediately or after a 24-hr delay. After this training normal rats show a strong selection preference for the trained food odor. (B) The effects of hippocampal lesions on performance in the retention test. Retention was intact immediately after learning but severely impaired during a 24-hr retention test.