An fMRI study of sex differences in brain activation during object naming.

We present a neuroimaging experiment that examines whether males and females use distinct brain systems while performing a confrontational naming task, with specific attention to the possibility of laterality differences, as suggested by some theories of sex differences in language processing. We further address whether sex-based differences in functional brain organization might interact with object category distinctions, given that previous behavioral studies have shown some consistent processing differences between the sexes with respect to tools versus plants. Functional magnetic resonance imaging (fMRI) data were collected from 26 participants (13 males and 13 females). Main effect and interaction analyses reveal no discernable laterality differences between the sexes. All other results, however, were consistent with previous object-naming studies. Global effects revealed dominant foci in fusiform gyrus, left posterior middle temporal gyrus, left basal ganglia/thalamus, left middle/inferior frontal gyri, left frontal operculum, left supplementary motor area/dorsal anterior cingulate, and left pre-central gyrus. Main contrasts for tools versus plants were likewise consistent with previous fMRI studies. Although men and women showed no discernable activation differences, hemispheric or otherwise, when collapsed across object categories, sex-by-category analyses showed selective activation for females in dorsal anterior cingulate gyrus and left posterior middle temporal gyrus for tools, and selective activation for males in left posterior middle temporal gyrus for plants. We discuss the relevance of these sex-by-category effects to previous behavioral findings and theories that relate to vocabulary differences between the sexes.