Abstract
An emerging literature suggests that the medial prefrontal cortex (mPFC) is crucial for the ability to track behavioral outcomes over time and has a critical role in successful foraging. Here, we examine this issue by analyzing changes in neuronal spike activity and local field potentials in the rat mPFC in relation to the consumption of rewarding stimuli. Using multi-electrode recording methods, we simultaneously recorded from ensembles of neurons and field potentials in the mPFC during the performance of an operant-delayed alternation task and a variable-interval licking procedure. In both tasks, we found that consummatory behavior (licking) activates many mPFC neurons and is associated with theta-band phase locking by mPFC field potentials. Many neurons that were modulated by the delivery of reward were also modulated when rats emitted bouts of licks during the period of consumption. The majority of these licking-modulated neurons were found in the rostral part of the prelimbic cortex, a region that is heavily interconnected with the gustatory insular cortex and projects to subcortical feeding-related centers. Based on the tight coupling between spike activity, theta-band phase locking, and licking behavior, we suggest that reward-related activity in the mPFC is driven by consummatory behavior.
Highlights
Successful foraging requires exploration of the surrounding environment, the capacity to remember where food/water was previously encountered, and the flexibility to adapt behavior in response to depleting resources or when confronted with competitors or predators (Stephens and Krebs, 1986)
We evaluated the role of the rat medial prefrontal cortex (mPFC) in reward processing during two tasks: an operant-delayed alternation task that depends on working memory and is disrupted following inactivation of the mPFC (Horst and Laubach, 2009) and a variable-interval licking procedure that required rats to stand at a spout and lick until fluid was delivered
We have previously reported that the largest fraction of event-modulated neurons in mPFC are sensitive to behavioral outcome in the delayed alternation task (Horst and Laubach, 2012)
Summary
Successful foraging requires exploration of the surrounding environment, the capacity to remember where food/water was previously encountered, and the flexibility to adapt behavior in response to depleting resources or when confronted with competitors or predators (Stephens and Krebs, 1986). Neuronal activity in the rat anterior cingulate cortex (ACC), posterior to the mPFC region studied in the Horst and Laubach study, reflects cost-benefit calculations based on the presence or absence of a competitor (Hillman and Bilkey, 2012; reviewed by Walton and Baudonnat, 2012). A recent human study reported ACC activity being greater when participants search for alternative options, and ventromedial PFC activity corresponds better with the final decision (Kolling et al, 2012). Each of these examples requires information gathering about the potential response options (locations), and the ability to detect and evaluate the outcome (reward)
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