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The Journal of Neuroscience, October 17, 2007, 27(42):11289-11295; doi:10.1523/JNEUROSCI.1914-07.2007

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Behavioral/Systems/Cognitive
Neurotoxic Lesions of the Medial Mediodorsal Nucleus of the Thalamus Disrupt Reinforcer Devaluation Effects in Rhesus Monkeys

Anna S. Mitchell, Philip G. F. Browning, and Mark G. Baxter

Department of Experimental Psychology, Oxford University, Oxford OX1 3UD, United Kingdom

Correspondence should be addressed to Dr. Anna S. Mitchell, Department of Experimental Psychology, Oxford University, South Parks Road, Oxford, OX1 3UD, UK.

The mediodorsal thalamus is a major input to the prefrontal cortex and is thought to modulate cognitive functions of the prefrontal cortex. Damage to the medial, magnocellular part of the mediodorsal thalamus (MDmc) impairs cognitive functions dependent on prefrontal cortex, including memory. The contribution of MDmc to other aspects of cognition dependent on prefrontal cortex has not been determined. The ability of monkeys to adjust their choice behavior in response to changes in reinforcer value, a capacity impaired by lesions of orbital prefrontal cortex, can be tested in a reinforcer devaluation paradigm. In the present study, rhesus monkeys with bilateral neurotoxic MDmc lesions were tested in the devaluation procedure. Monkeys learned visual discrimination problems in which each rewarded object is reliably paired with one of two different food rewards and then were given choices between pairs of rewarded objects, one associated with each food. Selective satiation of one of the food rewards reduces choices of objects associated with that food in normal monkeys. Monkeys with bilateral neurotoxic lesions of MDmc learned concurrently presented visual discrimination problems as quickly as unoperated control monkeys but showed impaired reinforcer devaluation effects. This finding suggests that the neural circuitry for control of behavioral choice by changes in reinforcer value includes MDmc.

Key words: amygdala; choice behavior; decision-making; devaluation; medial thalamus; orbitofrontal cortex; prefrontal cortex; reward

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Received April 27, 2007; revised Aug. 24, 2007; accepted Aug. 27, 2007.

Correspondence should be addressed to Dr. Anna S. Mitchell, Department of Experimental Psychology, Oxford University, South Parks Road, Oxford, OX1 3UD, UK.

This article has been cited by other articles:

				A. S. Mitchell, P. G. F. Browning, C. R. E. Wilson, M. G. Baxter, and D. Gaffan Dissociable Roles for Cortical and Subcortical Structures in Memory Retrieval and Acquisition J. Neurosci., August 20, 2008; 28(34): 8387 - 8396. [Abstract] [Full Text] [PDF]

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