Differential effects of inactivation of the orbitofrontal cortex on strategy set-shifting and reversal learning.

Full Abstract

Different subregions of the rodent prefrontal cortex (PFC) mediate dissociable types of behavioral flexibility. For example, lesions of the medial or orbitofrontal (OFC) regions of the PFC impair extradimensional shifts and reversal learning, respectively, when novel stimuli are used during different phases of the task. In the present study, we assessed the effects of inactivation of the OFC on strategy set-shifting and reversal learning, using a maze based set-shifting task mediated by the medial PFC. Long-Evans rats were trained initially on a visual-cue discrimination to obtain food. On the subsequent day, rats had to shift to using a response strategy (e.g., always turn left). On Day 3 (reversal), rats were required to reverse the direction of their turn (e.g., always turn right). Infusions of the local anesthetic bupivacaine into the OFC did not impair initial visual discrimination learning, nor did it impair performance on the set-shift. In contrast, inactivation of the OFC did impair reversal learning; yet, these rats ceased using the previously acquired response rule as readily as controls. Instead, rats receiving OFC inactivations made a disproportionate number of erroneous arm entries towards the visual-cue, suggested that these animals reverted back to using the original visual-cue based strategy. These findings, in addition to previous data, further support the notion that the OFC and medial PFC play dissociable roles in reversal learning and set-shifting. Furthermore, the lack of effect of OFC inactivations on the set-shift indicates that this type of behavioral flexibility does not require cognitive operations related to reversal learning.

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Author information

Author/s: Ghods-Sharifi, Sarvin (S); Haluk, Desirae M (DM); Floresco, Stan B (SB);

Affiliation: Department of Psychology and Brain Research Center, University of British Columbia, 2136 West Mall, Vancouver, BC, Canada V6T 1Z4.

Journal and publication information

Publication Type: Journal Article; Research Support, Non-U.S. Gov't

Journal: Neurobiology of learning and memory (Neurobiol Learn Mem), published in United States. (Language: eng)

Reference: 2008-May; vol 89 (issue 4) : pp 567-73

Dates: Created 2008/04/14; Completed 2008/07/15;

PMID: 18054257, status: MEDLINE (last retrieval date: 11/6/2008)

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Anesthetics, Local - pharmacology
Animals
Behavior, Animal - drug effects; physiology
Bupivacaine - pharmacology
Discrimination Learning - drug effects; physiology
Feeding Behavior - drug effects; physiology
Male

Maze Learning - drug effects; physiology
Photic Stimulation
Prefrontal Cortex - drug effects; physiology
Rats
Rats, Long-Evans
Reversal Learning - drug effects; physiology
Space Perception - drug effects; physiology

Associated Chemicals: Anesthetics, Local (0) ; Bupivacaine (2180-92-9)

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