Ventromedial frontal lobe damage disrupts value maximization in humans

Abstract

Recent work in neuroeconomics has shown that regions in orbitofrontal and medial prefrontal cortex encode the subjective value of different options during choice. However, these electrophysiological and neuroimaging studies cannot demonstrate whether such signals are necessary for value-maximizing choices. Here we used a paradigm developed in experimental economics to empirically measure and quantify violations of utility theory in humans with damage to the ventromedial frontal lobe (VMF). We show that people with such damage are more likely to make choices that violate the generalized axiom of revealed preference, which is the one necessary and sufficient condition for choices to be consistent with value maximization. These results demonstrate that the VMF plays a critical role in value-maximizing choice.

Figure 1.

Location and overlap of brain lesions of the nine subjects with VMF damage, projected on axial slices of the MNI brain. Different colors indicate the number of subjects who had damage involving a particular area in common, as indicated in the color key.

Figure 2.

a, Two examples of choices that violate GARP. Both were made by subject 6438. Left, choice 7 (red) violates GARP with respect to choice 1 (black). Right, choice 10 (red) violates GARP with respect to choice 5 (black). For each choice, the selected bundle is marked with a circle and all other bundles in the choice set are marked with crosses. A solid line connects all of the bundles in each choice set. The dotted red line illustrates how AEI is calculated in this case. b, The full set of choices made by four example subjects. The gray lines illustrate all 11 choice sets that each subject faced. Bundles that were selected are marked with circles, and those that were not selected are marked with crosses. Selections that violated GARP are shown in red, those that do not violate GARP are shown in black. The colored hashes through each circle clarify for which choice set(s) the bundle was selected. A control subject (6006) who made no GARP violations, the VMF subject (211) closest to the average number of GARP violations and AEI, the VMF subject (1403) with the most total violations, and the VMF subject (6438) with the smallest AEI are shown. c, Box-and-whisker plots of total number of GARP violations by group. The solid line shows the group mean, the surrounding boxes delimit the 25th to75th percentiles, and the whiskers the 10th to 90th percentiles.