Sex-related differences in interhemispheric transmission time in the human brain

Many studies on hemispheric specialization for language functions and on morphology of the corpus callosum have revealed stronger lateralization and smaller splenium area in men than in women. We have tested the related prediction that interhemispheric transmission times (IHTTs) of verbal information differ in the two sexes using event-related potentials (ERPs) for determining IHTTs in male and female subjects. The IHTTs were estimated as latency differences between early components of ERPs, recorded in response to words from symmetrical sites of directly and indirectly stimulated hemisphere, i.e. the hemisphere contralateral and ipsilateral to the visual hemifield of stimulus presentation. In women, IHTTs were similar for the left-to-right and right-to-left directions, whereas in men, IHTTs were directionally asymmetrical and were considerably longer for the left-to-right direction.