A computational model of the role of serotonin in reversal learning

Abstract

It has been shown that the action of serotonin on the orbito-frontal cortex (OFC) is crucial for the inhibition phase of reversal learning. Serotonin has also been shown to facilitate the induction of LTD throughout the prefrontal cortex. We present a biologically realistic, systems level model which proposes a mechanism for the release of serotonin in response to the omission of an expected reward. Serotonin release, as a result of the combination of excitation of the dorsal raphé nucleus (DRN) pathway and the lack of inhibition of the DRN from the lateral habenula, leads to LTD in the OFC and suppression of excitation of the nucleus accumbens shell due to reward predicting sensory stimuli. Behavioural inhibition is controlled via the shell-ventral pallido-mediodorsal pathway, which serves as a feed forward switching mechanism and enables the behavioural inhibition required to achieve reversal learning. © 2012 Springer-Verlag.