The contributions of lesion laterality and lesion volume to decision-making impairment following frontal lobe damage

Lesions to prefrontal cortex (PFC) in humans can severely disrupt everyday decision-making, with concomitant effects on social and occupational functioning. Forty-six patients with unilateral lesions to prefrontal cortex and 21 healthy control subjects were administered three neuropsychological measures of decision-making: the Iowa Gambling Task, the Cambridge Gamble Task, and the Risk Task. Magnetic resonance imaging (MRI) scans were acquired from 40 patients, with region of interest (ROI) mapping of prefrontal subregions. The frontal patients showed only limited damage in medial and orbital prefrontal cortex, but greater damage in lateral prefrontal regions of interest. Patients with right frontal lesions preferred the risky decks on the Iowa Gambling Task, and differed significantly from left frontal and control subjects. Within the right frontal group, the preference for the risky decks was correlated with the total lesion volume and the volume of damage outside of the ventromedial prefrontal region. Right and left frontal groups did not differ significantly on the Cambridge Gamble Task or the Risk Task, and performance was not associated with lesion volume. The results indicate a laterality effect on the Iowa Gambling Task, and the contribution of prefrontal regions outside the ventromedial region to task performance. The Cambridge Gamble Task and Risk Task were less sensitive to the effects of unilateral frontal lobe lesions, and may be more selectively associated with ventral prefrontal damage.