Sex differences in material-specific cognitive functions related to language dominance: an intracarotid amobarbital study in left temporal lobe epilepsy.

Population-based studies of material-specific cognitive functions yield evidence of sex differences: women are superior on verbal tasks whereas men are superior on figural and visuo-spatial tasks. Although there is still no direct evidence, these sex differences have been assumed to be related to a different cerebral organisation of language and nonlanguage functions, i.e. language in women is suggested to be more bilaterally organised than in men. We investigated this issue with respect to verbal/nonverbal memory functions in 42 men and 43 women with left temporal lobe epilepsies who all underwent intracarotid amobarbital testing for language dominance. The results indicate that atypical language dominance is not significantly more frequent in women than in men (44% vs 33%). Atypical dominance was related to an onset of epilepsy before puberty and appeared to be a consequence of the left hemisphere pathology rather than being naturally predisposed. Furthermore, women indeed showed the expected advantage with respect to verbal memory, and men showed an advantage in figural memory. With consideration of language dominance, however, the sex difference in verbal memory was observed particularly with atypical dominance, whereas the sex difference in figural memory was observed with left dominance.