Conflicting processes in the extinction of conditioned taste aversion: behavioral and molecular aspects of latency, apparent stagnation, and spontaneous recovery.
The study of experimental extinction and of the spontaneous recovery of the extinguished memory could cast light on neurobiological mechanisms by which internal representations compete to control behavior. In this work, we use a combination of behavioral and molecular methods to dissect subprocesses of experimental extinction of conditioned taste aversion (CTA). Extinction of CTA becomes apparent only 90 min after the extinction trial. This latency is insensitive to muscarinic and beta-adrenergic modulation and to protein synthesis inhibition in the insular cortex (IC). Immediately afterwards, however, the extinguishing trace becomes sensitive to beta-adrenergic blockade and protein synthesis inhibition. The subsequent kinetics and magnitude of extinction depend on whether a spaced or massed extinction protocol is used. A massed protocol is highly effective in the short run, but results in apparent stagnation of extinction in the long-run, which conceals fast spontaneous recovery of the preextinguished trace. This recovery can be truncated by a beta-adrenergic agonist or a cAMP analog in the insular cortex, suggesting that spontaneous overtaking of the behavioral control by the original association is regulated at least in part by beta-adrenergic input, probably operating via the cAMP cascade, long after the offset of the conditioned stimulus. Hence, the performance of the subject in experimental extinction is the sum total of multiple, sometimes conflicting, time-dependent processes.
Berman
Diego E
DE
Department of Neurobiology, The Weizmann Institute of Science, Rehovot 76100, Israel.
Hazvi
Shoshi
S
Stehberg
Jimmy
J
Bahar
Amir
A
Dudai
Yadin
Y
D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology; D000242:Cyclic AMP / Q000819:agonists / Q000378:metabolism / Q000502:physiology; D005108:Extinction, Psychological / Q000502:physiology*; D008297:Male; D008568:Memory / Q000502:physiology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000378:metabolism; D013649:Taste; D013997:Time Factors
D011500:Protein Synthesis Inhibitors; D011943:Receptors, Adrenergic, beta; D011976:Receptors, Muscarinic; D000242:Cyclic AMP