Sex differences in the persistence of the amygdala response to negative material

Abstract

Previous studies have indicated that men and women have different amygdala responses to novel (vs familiar) and valenced (positive vs negative) material. It is not known, however, whether these affective sex differences are related. In this study, we tested whether women have more persistent amygdala responses to familiar, negative material than men do. During fMRI, male and female participants viewed evocative images that varied in novelty and valence. Women and men showed equivalent responses to novel negative material, but women showed a sustained amygdala response to familiar negative material relative to men, indicating that women's amygdala responses were more persistent over multiple repetitions of negative material. Individuals with more persistent amygdala responses also reported greater levels of negative effect. These findings have implications for sex differences in the incidence of affective disorders.

Keywords: amygdala; habituation; sex.

Fig. 1

Average amygdala % signal change from baseline vs fixation to familiar (a,b) and novel (c,d) stimuli in the left (a,c) and right (b,d) amygdalae. * = P < 0.05.

Fig. 2

Clusters in bilateral amygdalae showing significantly greater signal change between novel negative and familiar negative items for men relative to women (blue). The only region where novel-familiar signal difference is greater in women, right insula, is also visible (red).

Fig. 3

Relationship between STAI scores and the signal change difference between novel and familiar negative items in (a) left and (b) right amygdalae. A smaller signal change difference represents a more persistent amygdala response.

Fig. 4

Relationship between CES-D scores and the signal change difference between novel and familiar negative items in (a) left and (b) right amygdalae. A smaller signal change difference represents a more persistent amygdala response.