ABSTRACT
Rodent dorsal medial prefrontal cortex (mPFC), typically prelimbic cortex, is often described as promoting actions such as reward seeking, whereas ventral mPFC, typically infralimbic cortex, is thought to promote response inhibition. However, both dorsal and ventral mPFC are necessary for both expression and suppression of different behaviors, and each region may contribute to different functions depending on the specifics of the behavior tested. To better understand the roles of dorsal and ventral mPFC in motivated behavior we pharmacologically inactivated each area during operant fixed ratio 1 (FR1) seeking for a natural reward (sucrose), extinction, cue-induced reinstatement, and progressive ratio sucrose seeking in male Long-Evans rats. Bilateral inactivation of dorsal mPFC, but not ventral mPFC increased reward seeking during FR1. Inactivation of both dorsal and ventral mPFC decreased seeking during extinction. Bilateral inactivation of ventral mPFC, but not dorsal mPFC decreased reward seeking during cue-induced reinstatement. No effect of inactivation was found during progressive ratio. Our data contrast sharply with observations seen during drug seeking and fear conditioning, indicating that previously established roles of dorsal mPFC = going vs. ventral mPFC = stopping are not applicable to all motivated behaviors and/or outcomes. Our results indicate that dichotomous functions of dorsal vs. ventral mPFC, if they exist, may align better with other models, or may require the development of a new framework in which these multifaceted brain areas play different roles in action control depending on the behavioral context in which they are engaged.
SIGNIFICANCE STATEMENT Dorsal and ventral medial prefrontal cortex have been proposed to control response execution and inhibition, respectively, in contexts such as drug seeking and fear learning. It is unclear, however, whether these roles are generalizable to all behaviors. We found that these opposing roles were not present during natural reward (sucrose) seeking, in contrast with previous drug seeking and fear conditioning literature. Dorsal and ventral mPFC inactivation did impact multiple aspects of seeking, but not in the bidirectional fashion predicted by a generalized go stop model. We conclude that, although these brain areas are clearly important in reward seeking, the dichotomous roles proposed previously are not broadly applicable, and mPFC contributions to these and related behaviors should be reconsidered.
Footnotes
The authors report no conflict of interest.
PHS research grants AA024571, AA025481, and DA041674, a NARSAD Young Investigator Grant from the Brain & Behavior Research Foundation (DEM), NS082179 (LR-H), and an SDI-STEM Diversity Institute Grant # S1111000000063 (JPC).
This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International license, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.
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