Lateral entorhinal cortex lesions impair odor‐context associative memory in male rats

• Published in: Journal of neuroscience research Vol. 100; no. 4; pp. 1030 - 1046
• Main Authors: Persson, Bjorn M., Ambrozova, Veronika, Duncan, Stephen, Wood, Emma R., O’Connor, Akira R., Ainge, James A.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.04.2022; John Wiley and Sons Inc
• Subjects: Animals; Associative memory; Chemical stimuli; Context; Cortex (entorhinal); Entorhinal Cortex; episodic memory; Excitotoxicity; Experiments; Hippocampus; Information processing; Lesions; Male; Males; Memory; Odor control; odor memory; Odorants; Odors; Olfactory discrimination; Olfactory discrimination learning; Rats; recognition memory; Rodents; RRID:AB_2298772; RRID:SCR_013672; RRID:SCR_018321; RRID:SCR_019096; Spatial data; Surgery; episodic memory; hippocampus; RRID:AB_2298772; RRID:SCR_013672; context; RRID:SCR_018321; odor memory; recognition memory; RRID:SCR_019096
• ISSN: 0360-4012; 1097-4547; 1097-4547
• DOI: 10.1002/jnr.25027

Lateral entorhinal cortex (LEC) has been hypothesized to process nonspatial, item information that is combined with spatial information from medial entorhinal cortex to form episodic memories within the hippocampus. Recent studies, however, have demonstrated that LEC has a role in integrating features of episodic memory prior to the hippocampus. While the precise role of LEC is still unclear, anatomical studies show that LEC is ideally placed to be a hub integrating multisensory information. The current study tests whether the role of LEC in integrating information extends to long‐term multimodal item‐context associations. In Experiment 1, male rats were trained on a context‐dependent odor discrimination task, where two different contexts served as the cue to the correct odor. Rats were pretrained on the task and then received either bilateral excitotoxic LEC or sham lesions. Following surgery, rats were tested on the previously learned odor‐context associations. Control rats showed good memory for the previously learned association but rats with LEC lesions showed significantly impaired performance relative to both their own presurgery performance and to control rats. Experiment 2 went on to test whether impairments in Experiment 1 were the result of LEC lesions impairing either odor or context memory retention alone. Male rats were trained on simple odor and context discrimination tasks that did not require integration of features to solve. Following surgery, both LEC and control rats showed good memory for previously learned odors and contexts. These data show that LEC is critical for long‐term odor‐context associative memory. Rats with lesions of lateral entorhinal cortex have impaired memory for associations of odors and contexts while their memory for individual items is unaffected. This suggests that integration of associative information occurs at the level of lateral entorhinal cortex as well as the hippocampus.