Ventromedial frontal lobe damage disrupts the accuracy, but not the speed, of value-based preference judgments

Abstract

The ventromedial frontal lobe (VMF) plays a role in decision making, but its precise function remains unclear. Several lines of evidence suggest that VMF is involved in representing the economic value of options. A prior study from our lab has shown that patients with lesions to the VMF are less consistent than controls in making simple preference judgments between stimuli presented in pairs. Here, we followed up that observation in a larger sample, using more sensitive tasks, and examining the category-specificity of this effect. Patients with damage to VMF (N=15) were compared to patients with frontal damage sparing that region (N=8) and to demographically matched healthy control participants (N=23). Five separate preference tasks were administered, requiring subjects to indicate their preference for 12 stimuli presented two at a time, in all possible combinations. Categories included fruits, vegetables, colors, landscapes, and puppies. Choices were analyzed for internal consistency, and decision times were measured. Three control tasks with the same format, but requiring perceptual judgments, were also administered. VMF patients were significantly more erratic than both non-VMF and healthy control participants in their preference judgments across all stimulus categories. However, decision times, and the relationship between decision time and relative value, were similar to that seen in control participants. The groups did not differ in perceptual judgment performance. These findings add further weight to the claim that VMF plays a critical role in simple value-based decision-making under conditions of certainty. This region appears to be necessary for consistent choices across a variety of stimulus categories, supporting the view that human VMF represents the (relative) value of decision options rather generally. That such damage impairs decision 'accuracy' without affecting reaction time has implications for theories of the role of VMF in decision-making, arguing that this region may be critical for linking a particular value to a particular option.