Differential effects of damage within the hippocampal region on memory for a natural, nonspatial Odor-Odor Association

Abstract

Debate continues on whether the role of rodent hippocampus in memory is limited to the spatial domain. Recently, this controversy has been addressed with studies on the social transmission of food preference, an odor-odor association task with no spatial requirements. Multiple reports have concluded that damage to the hippocampal region impairs memory in this task, but there remain questions about the extent of damage essential to produce an impairment. Furthermore, a recent study () found no effect of hippocampal lesions on memory in this task. We tested animals with complete lesions of the hippocampus (H) lesions of the hippocampus plus subiculum (HS), and lesions of the adjacent, anatomically related cortices of the parahippocampal region (PHR). H lesions produced an impairment on spatial delayed alternation, but not on memory for the social transmission of food preference, whereas HS and PHR lesions produced severe and equivalent impairments on memory for the socially acquired food preference. We discuss possible explanations for the discrepancy with the results of and conclude that the hippocampus and subiculum together play a critical role in the formation of this form of nonspatial, relational memory.

Figure 1

Extent of the smallest (vertical hatching) and largest (diagonal) lesions in each group. Numbers indicate millimeters posterior to bregma.

Figure 2

Performance on behavioral tasks. (A) Social transmission of food preference. Asterisks indicate a significant difference from both the H and N groups. (B) Delayed spatial alternation. All data are presented as mean +  S.E.M. On both tasks, 50% represents chance performance.