Abstract
The medial frontal cortex (MFC) is critical for cost–benefit decision-making. Generally, cognitive and reward-based behaviour in rodents is not thought to be lateralised within the brain. In this study, however, we demonstrate that rats with unilateral MFC lesions show a profound change in decision-making on an effort-based decision-making task. Furthermore, unilateral MFC lesions have a greater effect when the rat has to choose to put in more effort for a higher reward when it is on the contralateral side of space to the lesion. Importantly, this could not be explained by motor impairments as these animals did not show a turning bias in separate experiments. In contrast, rats with unilateral dopaminergic midbrain lesions did exhibit a motoric turning bias, but were unimpaired on the effort-based decision-making task. This rare example of a cognitive deficit caused by a unilateral cortical lesion in the rat brain indicates that the MFC may have a specialised and lateralised role in evaluating the costs and benefits of actions directed to specific spatial locations.
Highlights
Neural circuits comprising the medial frontal cortex (MFC), the core subregion of the nucleus accumbens (NAc) and midbrain dopaminergic projections from the ventral tegmental area (VTA) are important in evaluating how much effort to expend for reward (Floresco et al, 2008; Botvinick et al, 2009; Hillman & Bilkey, 2010)
All rats that were lesioned were included in the behavioural analyses
We unexpectedly found that unilateral excitotoxic lesions of the MFC caused rats to alter their choice behaviour in an effortbased decision-making paradigm
Summary
Neural circuits comprising the medial frontal cortex (MFC), the core subregion of the nucleus accumbens (NAc) and midbrain dopaminergic projections from the ventral tegmental area (VTA) are important in evaluating how much effort to expend for reward (Floresco et al, 2008; Botvinick et al, 2009; Hillman & Bilkey, 2010). Rather than causing cost aversion per se, lesions and/or inactivations of the MFC (and of the dorsal anterior cingulate cortex) impair rats’ ability to overcome a particular type of cost, namely effort, to gain a greater benefit when there is a smaller, more obtained reward available (Walton et al, 2003; Schweimer & Hauber, 2005; Rudebeck et al, 2006; Floresco & Ghods-Sharifi, 2007). A similar finding has been observed in the T-maze choice task after disrupting dopamine (DA) transmission systemically or by targeted dopaminergic lesions in NAc (Salamone & Correa, 2012). In one study, Hauber & Sommer (2009) showed that disconnection of the NAc and anterior cingulate cortex, using an asymmetrical (contralateral), excitotoxic
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