Different contributions of the human amygdala and ventromedial prefrontal cortex to decision-making

The somatic marker hypothesis proposes that decision-making is a process th at depends on emotion. Studies have shown that damage of the ventromedial p refrontal (VMF) cortex precludes the ability to use somatic (emotional) sig nals that are necessary for guiding decisions in the advantageous direction . However, given the role of the amygdala in emotional processing, we asked whether amygdala damage also would interfere with decision-making. Further more, we asked whether there might be a difference between the roles that t he amygdala and VMF cortex play in decision-making. To address these two qu estions, we studied a group of patients with bilateral amygdala, but not VM F, damage and a group of patients with bilateral VMF, but not amygdala, dam age. We used the "gambling task" to measure decision-making performance and electrodermal activity (skin conductance responses, SCR) as an index of so matic state activation. All patients, those with amygdala damage as well as those with VMF damage, were (1) impaired on the gambling task and (2) unab le to develop anticipatory SCRs while they pondered risky choices. However, VMF patients were able to generate SCRs when they received a reward or a p unishment (play money), whereas amygdala patients failed to do so. in a Pav lovian conditioning experiment the VMF patients acquired a conditioned SCR to visual stimuli paired with an aversive loud sound, whereas amygdala pati ents failed to do so. The results suggest that amygdala damage is associate d with impairment in decision-making and that the roles played by the amygd ala and VMF in decision-making are different.