A role for olfaction in object recognition by normal and hippocampal-damaged rats

To examine how olfactory and visual factors affect object discriminations in rats with and without hippocampus damage, the authors trained Long-Evans rats on simple object discriminations. They then examined how these discriminations were affected by rotations of the objects, by coating the objects in a transparent acrylic coating, or by both rotating and coating the objects in acrylic. The rats displayed no impairments when the objects were only sprayed in acrylic, and they displayed minor impairments when the objects were rotated. However, when the objects were both rotated and acrylic coated, the rats displayed severe impairments. This suggests that the rats are solving the rotated-only phase based on surface features of the objects (probably odor) and not based on the visual information. Such species' biases for obtaining object information are important factors to consider when designing and interpreting visual memory experiments across species. There was no difference in performance between the rats with hippocampus damage and the sham rats, and this is consistent with the literature on similar tasks.