The role of the rat prelimbic (PL) and infralimbic (IL) in action selection and extinction
Summary
The prefrontal cortex is thought to be highly involved in the process of selecting situation appropriate actions. In the rat PFC, a functional dichotomy has been proposed, where the infralimbic cortex (IL) inhibits actions, and the prelimbic cortex (PL) promotes action. However, this dichotomy has been challenged by multiple studies suggesting that both IL and PL encode context appropriate behaviour and inhibit situation inappropriate behaviour. Further research is needed to understand the role of IL and PL in guiding action selection. Therefore, in this study, we use a Go/No-Go rat model to investigate the role of the IL and PL in action selection. The Go/No-Go task was designed so animals had to either initiate an or inhibit action, based on cues that signal situation appropriate action to earn a reward. We perturbated IL, PL and IL + PL using two Designer Receptor Exclusively Activated by Designer Drugs (DREADDs), in order to understand their role in the Go/No-Go behavioural paradigm. This experimental set-up allowed us to investigate the role of the IL and PL in selecting situation appropriate actions and inhibiting situation inappropriate actions. Additionally, it allowed us to investigate the role of the IL in extinction learning, by extinction of the Go response. Following the hypothesized functional dichotomy, one would expect inhibition of PL to result in a worse Go performance, and inhibition of IL to result in a worse No-Go performance. Thereby, given the role of the IL in inhibition of inappropriate action, IL inhibition was expected to negatively affect extinction learning. We observed that Go performance was significantly affected, while sparing No-Go performance, especially after inhibition of both IL and PL. Decreased Go performance seemed to be caused by an impaired ability of the animals to flexibly change behaviour while making a nose-poke response, suggesting that action initiation was impaired due to perturbation of these two regions. However, several limitations in this study complicated interpretation of our results: The effects on our behavioural measurements of the two drugs used to inhibit the two regions differed, general movement deficits due to inhibition of IL and PL seem to confound our observations and histological analysis is not completed yet. These limitations should be tackled in a follow-up study in order to find out what the effects of IL and PL inhibition are on behaviour in the Go/No-Go task.