A voxel-by-voxel parametric fMRI study of motor mental rotation: hemispheric specialization and gender differences in neural processing efficiency.

Differences between men and women in brain size, cognitive performance and lateralization of brain activation have been perennial and controversial issues. Here we show that in a motor mental rotation task where women and men performed equally well, the slope of the functional magnetic resonance imaging (fMRI) blood oxygenation level dependent (BOLD) signal per degree of mental rotation was overall 2.4x higher in men than in women. This was attributed to the much more inefficient engagement (i.e. higher slopes) of the right hemisphere by men (mainly the frontal lobe). These findings indicate that women process information much more efficiently than men, which could offset smaller brain size.