Brain Advance Access originally published online on April 3, 2008
Brain 2008 131(5):1311-1322; doi:10.1093/brain/awn066
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Differential effects of insular and ventromedial prefrontal cortex lesions on risky decision-making
1Behavioural and Clinical Neuroscience Institute, 2Department of Experimental Psychology, University of Cambridge, Cambridge, UK, 3Brain and Creativity Institute and Dornsife Imaging Center, University of Southern California, Los Angeles, CA, 4Department of Neurology, University of Iowa Hospitals and Clinics, Iowa City, IA, USA and 5Department of Psychiatry, University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Cambridge, UK
Correspondence to: Dr Luke Clark, Behavioural and Clinical Neuroscience Institute, Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge, UK E-mail: lc260{at}cam.ac.uk
The ventromedial prefrontal cortex (vmPFC) and insular cortex are implicated in distributed neural circuitry that supports emotional decision-making. Previous studies of patients with vmPFC lesions have focused primarily on decision-making under uncertainty, when outcome probabilities are ambiguous (e.g. the Iowa Gambling Task). It remains unclear whether vmPFC is also necessary for decision-making under risk, when outcome probabilities are explicit. It is not known whether the effect of insular damage is analogous to the effect of vmPFC damage, or whether these regions contribute differentially to choice behaviour. Four groups of participants were compared on the Cambridge Gamble Task, a well-characterized measure of risky decision-making where outcome probabilities are presented explicitly, thus minimizing additional learning and working memory demands. Patients with focal, stable lesions to the vmPFC (n = 20) and the insular cortex (n = 13) were compared against healthy subjects (n = 41) and a group of lesion controls (n = 12) with damage predominantly affecting the dorsal and lateral frontal cortex. The vmPFC and insular cortex patients showed selective and distinctive disruptions of betting behaviour. VmPFC damage was associated with increased betting regardless of the odds of winning, consistent with a role of vmPFC in biasing healthy individuals towards conservative options under risk. In contrast, patients with insular cortex lesions failed to adjust their bets by the odds of winning, consistent with a role of the insular cortex in signalling the probability of aversive outcomes. The insular group attained a lower point score on the task and experienced more ‘bankruptcies’. There were no group differences in probability judgement. These data confirm the necessary role of the vmPFC and insular regions in decision-making under risk. Poor decision-making in clinical populations can arise via multiple routes, with functionally dissociable effects of vmPFC and insular cortex damage.
Key Words: risk; uncertainty; orbitofrontal cortex; neuropsychology; emotion
Abbreviations: CT, computed tomography; fMRI, functional magnetic resonance imaging; SII, somatosensory cortex; vmPFC, ventromedial prefrontal cortex
Received December 17, 2007. Revised March 6, 2008. Accepted March 10, 2008.
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