The Journal of Neuroscience, April 8, 2009, 29(14):4346-4350; doi:10.1523/JNEUROSCI.0069-09.2009
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Brief Communications
Muscarinic Receptors in Perirhinal Cortex Control Trace Conditioning
Sun Jung Bang1 and
Thomas H. Brown1,2
Departments of 1Psychology and 2Cellular and Molecular Physiology, Yale University, New Haven, Connecticut 06520
Correspondence should be addressed to Thomas H. Brown, Department of Psychology, Yale University, 2 Hillhouse Avenue, New Haven, CT 06520. Email: thomas.brown{at}yale.edu
Trace conditioning requires that a transient representation of the conditional stimulus (CS) persists during the time interval between the CS offset and the onset of the unconditional stimulus. According to one hypothesis, this transient CS representation is supported by endogenous activity in "persistent-firing" neurons of perirhinal cortex (PR). By definition, persistent-firing neurons discharge for tens of seconds or minutes after the termination of the original spike-initiating stimulus. This continued spiking does not depend on recurrent circuit activity and can be reliably and completely blocked by muscarinic receptor antagonists. The present study evaluated the role of PR muscarinic receptors in trace fear conditioning. Before conditioning, rats received bilateral intra-PR infusions with either saline or scopolamine, a nonselective muscarinic receptor antagonist. Scopolamine infusions profoundly impaired trace conditioning but had no effect on delay conditioning or context conditioning. The results encourage a more general understanding of muscarinic receptors in PR and they motivate additional tests of the emerging theory that persistent-firing neurons support aspects of transient memory.
Received Jan. 6, 2009;
revised Feb. 17, 2009;
accepted March 4, 2009.
Correspondence should be addressed to Thomas H. Brown, Department of Psychology, Yale University, 2 Hillhouse Avenue, New Haven, CT 06520. Email: thomas.brown{at}yale.edu
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