Corresponding: Sex Differences In Amygdala

NEUROREPORT

MOTIVATION, EMOTION, FEEDING, DRINKING

Sex differences in amygdala activation during the perception of facial affect
William D. S. KillgoreCA and Deborah A. Yurgelun-Todd
Cognitive Neuroimaging Laboratory, Brain Imaging Center, McLean Hospital/Harvard Medical School, 115 Mill Street, Belmont,
MA 02478, USA
CA

Corresponding Author

Received 11 April 2001; accepted 5 June 2001

The cognitive and affective systems of the cerebral cortex are often more lateralized in males than females, but it is unclear whether these differences extend to subcortical systems. We used fMRI to examine sex differences in lateralized amygdala activity during happy and fearful face perception. Amygdala activation differed for men
There is some evidence of a lateralized pattern of amygdala activity during affective processing, with several studies ®nding greater left than right amygdala activation during negative emotional facial expressions such as fear [12], and sex differences in this lateralized activity may be evident as early as adolescence [13]. In contrast to negative emotions, there have been few studies examining the functional responsiveness of the amygdala to positive emotions such as happiness. The laterality of amygdala activation during the perception of happy faces has been less consistent than the ®ndings for fearful faces [12,14] and no functional imaging studies have speci®cally examined the in¯uence of sex differences on the activation of the amygdala during the perception of either happy or fearful faces. We chose to examine whether the theory of sex-dependent lateralization of function that accounts for ®ndings within the neo-cortex

Vol 12 No 11 8 August 2001

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NEUROREPORT could be extended to also account for subcortical processing of affective
The present ®ndings further suggest that the asymmetry of amygdala activation may follow a pattern of sex dependent lateralization analogous to that seen in higher regions of the cerebral cortex, with males typically showing greater lateralized function relative to females, who tend to show a more bilateral pattern of function.
The present study represents the ®rst attempt to use fMRI to characterize sex differences in amygdala responsiveness to faces expressing valence speci®c affect. Obviously, the limited number of males and females in each group temper these results and additional studies will be needed with larger samples in order to establish the generalizability of these ®ndings. Furthermore, in the present study, we employed a simple visual ®xation point as the control baseline condition rather than the use of a neutral face. While this strategy maximized our possibility of detecting signal changes for each valence condition and permitted the direct comparison of fearful and happy activation within the ROIs, we were not able to make the tighter task comparison that could be accomplished