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Cerebral Cortex Advance Access published online on November 5, 2009
Cerebral Cortex, doi:10.1093/cercor/bhp250
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© The Author 2009. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org

Prefrontal Cortical Contribution to Risk-Based Decision Making

Jennifer R. St. Onge and Stan B. Floresco

Department of Psychology and Brain Research Center, University of British Columbia, Vancouver, BC, Canada V6T 1Z4

Address correspondence to Stan B. Floresco, PhD, Department of Psychology and Brain Research Center, University of British Columbia, 2136 West Mall, Vancouver BC V6T 1Z4, Canada. Email: floresco{at}psych.ubc.ca.

Damage to various regions of the prefrontal cortex (PFC) impairs decision making involving evaluations about risks and rewards. However, the specific contributions that different PFC subregions make to risk-based decision making are unclear. We investigated the effects of reversible inactivation of 4 subregions of the rat PFC (prelimbic medial PFC, orbitofrontal cortex [OFC], anterior cingulate, and insular cortex) on probabilistic (or risk) discounting. Rats were well trained to choose between either a "Small/Certain" lever that always delivered 1 food pellet, or another, "Large/Risky" lever, which delivered 4 pellets, but the probability of receiving reward decreased across 4 trial blocks (100%, 50%, 25%, and 12.5%). Infusions of gama-aminobutyric acid agonists muscimol/baclofen into the medial PFC increased risky choice. However, similar medial PFC inactivations decreased risky choice when the Large/Risky reward probability increased over a session. OFC inactivation increased response latencies in the latter trial blocks without affecting choice. Anterior cingulate or insular inactivations were without effect. The effects of prelimbic inactivations were not attributable to disruptions in response flexibility or judgments about the relative value of probabilistic rewards. Thus, the prelimbic, but not other PFC regions, plays a critical role in risk discounting, integrating information about changing reward probabilities to update value representations that facilitate efficient decision making.

Key Words: anterior cingulate • orbitofrontal cortex • prelimbic cortex • reversible inactivation • rat


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