A molecular mechanism underlying gustatory memory trace for an association in the insular cortex

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Abstract

Events separated in time are associatively learned in trace conditioning, recruiting more neuronal circuits and molecular mechanisms than in delay conditioning. However, it remains unknown whether a given sensory memory trace is being maintained as a unitary item to associate. Here, we used conditioned taste aversion learning in the rat model, wherein animals associate a novel taste with visceral nausea, and demonstrate that there are two parallel memory traces of a novel taste: a short-duration robust trace, lasting approximately 3h, and a parallel long-duration weak one, lasting up to 8h, and dependent on the strong trace for its formation. Moreover, only the early robust trace is maintained by a NMDAR-dependent CaMKII- AMPAR pathway in the insular cortex. These findings suggest that a memory trace undergoes rapid modifications, and that the mechanisms underlying trace associative learning differ when items in the memory are experienced at different time points.

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Chinnakkaruppan Adaikkan

Sagol Department of Neurobiology, University of Haifa, Haifa, Israel

Competing interests
The authors declare that no competing interests exist.
Kobi Rosenblum

Sagol Department of Neurobiology, University of Haifa, Haifa, Israel

For correspondence
kobir@psy.haifa.ac.il

Competing interests
The authors declare that no competing interests exist.

Ethics

Animal experimentation: The procedures were approved by the University of Haifa ethics committee for animal research and were in accordance with the NIH guidelines for the ethical treatment of animals. All of the animals were handled according to the Haifa University animal care and use committee. All surgery was preformed under sodium pentobarbital anesthesia, and every effort was made to minimize suffering.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.