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5. Differential Involvement of the Medial Prefrontal Cortex across Variants of Contextual Fear Conditioning

Author

Heroux, Nicholas A., Robinson-Drummer, Patrese A., Sanders, Hollie R., Rosen, Jeffrey B., and Stanton, Mark E.

Abstract

The context preexposure facilitation effect (CPFE) is a contextual fear conditioning paradigm in which learning about the context, acquiring the context-shock association, and retrieving/expressing contextual fear are temporally dissociated into three distinct phases. In contrast, learning about the context and the context-shock association happens concurrently in standard contextual fear conditioning (sCFC). By infusing the GABAA receptor agonist muscimol into medial prefrontal cortex (mPFC) in adolescent Long-Evans rats, the current set of experiments examined the functional role of the mPFC in each phase of the CPFE and sCFC. In the CPFE, the mPFC is necessary for the following: acquisition and/or consolidation of context memory (Experiment 1), reconsolidation of a context memory to include shock (Experiment 2), and expression of contextual fear memory during a retention test (Experiment 3). In contrast to the CPFE, inactivation of the mPFC prior to conditioning in sCFC has no effect on acquisition, consolidation, or retention of a contextual fear memory (Experiment 4). Interestingly, the mPFC is not required for acquiring a context-shock association (measured by post-shock freezing) in the CPFE or sCFC (Experiment 2b and 4). Taken together, these results indicate that the mPFC is differentially recruited across stages of learning and variants of contextual fear conditioning (CPFE versus sCFC). More specifically, separating out learning about the context and the context-shock association necessitates activation of the medial prefrontal cortex during early learning and/or consolidation.

Published
2017
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8. Spatial Discrimination Reversal Learning in Weanling Rats Is Impaired by Striatal Administration of an NMDA-Receptor Antagonist

Author

Watson, Deborah J. and Stanton, Mark E.

Abstract

The striatum plays a major role in both motor control and learning and memory, including executive function and "behavioral flexibility." Lesion, temporary inactivation, and infusion of an N-methyl-d-aspartate (NMDA)-receptor antagonist into the dorsomedial striatum (dmSTR) impair reversal learning in adult rats. Systemic administration of MK-801 disrupts reversal learning in developing rats, as reported in an earlier work by Chadman et al., but it is not known whether NMDA-receptor function within the dmSTR plays a role in this effect. In Experiment 1, reversal learning was dose-dependently impaired following bilateral dmSTR administration of MK-801 (either 2.5 or 5.0 [micro]g) only during the reversal phase relative to saline in postnatal day (P) 26 rats. In Experiment 2, separate groups of P26 rats were trained on the same reversal learning task, but were administered bilateral dmSTR infusions during acquisition only (MK-SAL), reversal only (SAL-MK), both phases (MK-MK), or neither phase (SAL-SAL). The MK-801 effect was specific to the reversal training phase. The drug did not alter acquisition of the initial discrimination. Analysis of the pattern of errors indicates that dmSTR MK-801 treatment increased perseveration of the choice response trained in acquisition. NMDA receptors in the dmSTR play a role in reversal learning in the weanling rat.

Published
2009
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30. Ontogeny of Multiple Memory Systems

Author

Blumberg, Mark S., primary, Freeman, John H., additional, Robinson, Scott R., additional, Stanton, Mark E., additional, Ivkovich Claflin, Dragana, additional, and Herbert, Jane, additional

Published
2009
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