Sex differences in lateralization revealed in the posterior language areas.

It has been hypothesized that language functions are more strongly lateralized to the left hemisphere in males than in females. Previous anatomical data and patient studies have suggested that the posterior language areas should exhibit sex differences. However, neuroimaging studies to date have only provided support for differences in the anterior language areas. To look for differences in the posterior language areas, functional magnetic resonance imaging scans were obtained while male and female subjects listened attentively to a story read aloud and to the same story replayed in reverse. Comparing activation in the superior and the middle temporal gyri during a story to activation during reverse replay of the story showed lateralization to the left in males but not in females. There was no lateralization in either sex when comparing activation during random fragmentation of the story to reverse replay. In the angular and the supramarginal gyri, however, activation was lateralized to the left hemisphere in both sexes, unlike the sex-dependent activation of the posterior temporal lobes. We infer that females use the posterior temporal lobes more bilaterally during linguistic processing of global structures in a narrative than males do.