Economic and moral decision-making after damage to the basolateral amygdala

Prof. Jack van Honk (Utrecht University, University of Cape Town)

1 octobre 2013, 16h, Uni-Mail M5193

Present-day models hold that instrumental (calculative) and impulsive (affective) behaviors underlie human social-economic and moral decision-making. The amygdala is assumed to play a role in social and moral decision-making, but the details are poorly understood. Problematically, the human amygdala mostly is investigated and discussed as a single unit. A blind eye is turned to rodent research, which suggests that the basolateral amygdala (BLA) subserves instrumental choice behaviors and regulates the central-medial amygdala, which sub-serves impulsive choice behaviors. If these rodent data hold relevance to the human brain selective dysfunction of the human BLA should constrain instrumental economic and utilitarian moral decisions. I will present data from a group of subjects from the Northern-Cape mountain deserts of South Africa (Namaqualand), with a knock-out-of-function mutation of the ECM1 gene (Urbach-Wiethe disease; UWD). In this South-African UWD group the mutation results in selective bilateral damage to exclusively the basolateral region of the amygdala, with other amygdala regions remaining intact and functional. Our BLA- damaged subjects invest nearly 100% more money in unfamiliar others in a trust game than do control-subjects, and this generosity is not caused by the expectation of higher returns or risk-taking deviations in nonsocial contexts. Their generous investments apparently are not instrumental, but seem altruistic in nature. Furthermore, these BLA-damaged subjects also differ strongly from control subjects in moral decision-making, in that they show substantially less utilitarian decisions in life-and-death moral dilemmas. Together these findings imply that the human BLA is essential for instrumental choices in social-economic and moral decision-making.