Combined lesions of hippocampus and subiculum do not produce deficits in anonspatial social olfactory memory task

Rats transmit information to each other about which foods are safe to eat. If a rat smells a food odor on the breath of another rat, it is subsequentl y more likely to eat that food than an alternative. Work by Galef et al. (1 988) has shown that the observer rat forms an association between two olfac tory stimuli on the breath of the demonstrator rat that has eaten the food, the food odor and carbon disulphide, which is normally present in the rat breath. Bunsey and Eichenbaum (1995) claimed that the hippocampus/subicular region is required for the long-term retention of this nonspatial form of associative memory on the basis that combined lesions of the hippocampus an d subiculum produced a deficit, but lesions of either structure alone did n ot. We report here a failure to repeat this finding. Rats with either combi ned lesions of the hippocampus and subiculum or with amygdala lesions were tested on their ability to remember this association either immediately (te sting short-term memory) or after a 24 hr delay (testing long-term memory). Neither lesion group exhibited significant memory deficits on this nonspat ial associative task at either test interval. In contrast, a deficit was ob served on a spatial memory task (forced-choice alternation t-maze) for anim als with combined lesions of the hippocampus and subiculum. These results c ontradict the findings of Bunsey and Eichenbaum (1995) and support the idea that the hippocampus/subicular region is not required for this nonspatial associative memory.