Sex-related functional asymmetry of the amygdala: preliminary evidence using a case-matched lesion approach

We have reported previously that there appears to be an intriguing sex-related functional asymmetry of the prefrontal cortices, especially the ventromedial sector, in regard to social conduct, emotional processing, and decision-making, whereby the right-sided sector is important in men but not women and the left-sided sector is important in women but not men. The amygdala is another structure that has been widely implicated in emotion processing and social decision-making, and the question arises as to whether the amygdala, in a manner akin to what has been observed for the prefrontal cortex, might have sex-related functional asymmetry in regard to social and emotional functions. A preliminary test of this question was carried out in the current study, where we used a case-matched lesion approach and contrasted a pair of men cases and a pair of women cases, where in each pair one patient had left amygdala damage and the other had right amygdala damage. We investigated the domains of social conduct, emotional processing and personality, and decision-making. The results provide support for the notion that there is sex-related functional asymmetry of the amygdala in regard to these functions - in the male pair, the patient with right-sided amygdala damage was impaired in these functions, and the patient with left-sided amygdala damage was not, whereas in the female pair, the opposite pattern obtained, with the left-sided woman being impaired and the right-sided woman being unimpaired. These data provide preliminary support for the notion that sex-related functional asymmetry of the amygdala may entail functions such as social conduct, emotional processing, and decision-making, a finding that in turn could reflect (as either a cause or effect) differences in the manner in which men and women apprehend, process, and execute emotion-related information.