FACILITATION OF CONDITIONED ODOR AVERSION BY ENTORHINAL CORTEX LESIONS IN THE RAT

This study examined the role of the entorhinal cortex (EC) in conditio ned odor aversion learning (COA). Lateral EC lesions did not impair bu t rather facilitated COA. In the experiments the delay separating the odor cue presentation from the subsequent toxicosis was varied during acquisition. EC-lesioned rats demonstrated COA for delays up to 2 hr, whereas sham-operated rats displayed COA only if toxicosis immediately followed the odor cue. This facilitation was not dependent on the int ensity of the odor and corresponded to a facilitated long-delay learni ng. EC lesion did not affect conditioned taste aversion, confirming th at the facilitation effect does not correspond to a general facilitati on of conditioned aversion learning. Taken together, these results ind icate that the removal of the EC may allow odor-toxicosis associations across longer delays by extending the duration of the olfactory trace .