title: The role of the medial prefrontal cortex in updating reward value and avoiding perseveration.
abstract: The medial prefrontal cortex (mPFC) plays a major role in goal-directed behaviours, but it is unclear whether it plays a role in breaking away from a high-value reward in order to explore for better options. To address this question, we designed a novel 3-arm Bandit Task in which rats were required to choose one of three potential reward arms, each of which was associated with a different amount of food reward and time-out punishment. After a variable number of choice trials the reward locations were shuffled and animals had to disengage from the now devalued arm and explore the other options in order to optimise payout. Lesion and control groups' behaviours on the task were then analysed by fitting data with a reinforcement learning model. As expected, lesioned animals obtained less reward overall due to an inability to flexibly adapt their behaviours after a change in reward location. However, modelling results showed that lesioned animals were no more likely to explore than control animals. We also discovered that all animals showed a strong preference for certain maze arms, at the expense of reward. This tendency was exacerbated in the lesioned animals, with the strongest effects seen in a subset of animals with damage to dorsal mPFC. The results confirm a role for mPFC in goal-directed behaviours but suggest that rats rely on other areas to resolve the explore-exploit dilemma.
authors.affiliation: Department of Neuroscience, Canadian Centre for Behavioural Neuroscience, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1K 3M4, Canada.
authors.forename: C S
authors.initials: CS
authors.lastname: Laskowski
authors.affiliation: Faculty of Health Science, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1K 3M4, Canada.
authors.forename: R J
authors.initials: RJ
authors.lastname: Williams
authors.affiliation: Department of Pathology and Laboratory Medicine, School of Medicine, University of British Columbia, 2211 Wesbrook Mall, Vancouver, British Columbia V6T 2B5, Canada.
authors.forename: K M
authors.initials: KM
authors.lastname: Martens
authors.affiliation: Department of Neuroscience, Canadian Centre for Behavioural Neuroscience, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1K 3M4, Canada.
authors.forename: A J
authors.initials: AJ
authors.lastname: Gruber
authors.affiliation: Department of Neuroscience, Canadian Centre for Behavioural Neuroscience, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1K 3M4, Canada.
authors.forename: K G
authors.initials: KG
authors.lastname: Fisher
authors.affiliation: Department of Neuroscience, Canadian Centre for Behavioural Neuroscience, University of Lethbridge, 4401 University Drive, Lethbridge, Alberta T1K 3M4, Canada. Electronic address: david.euston@gmail.com.
authors.forename: D R
authors.initials: DR
authors.lastname: Euston
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000502:physiology*; D002755:Choice Behavior / Q000502:physiology; D003216:Conditioning, Operant / Q000502:physiology*; D004193:Discrimination Learning; D005508:Food Deprivation; D008297:Male; D018782:Maze Learning / Q000502:physiology; D017397:Prefrontal Cortex / Q000293:injuries / Q000502:physiology*; D051381:Rats; D020318:Rats, Long-Evans; D011930:Reaction Time / Q000502:physiology; D012201:Reward
keywords: Decision making; Exploration; Prefrontal cortex; Reinforcement learning; Reward; Value