Temporal lobe activation demonstrates sex-based differences during passivelistening

PURPOSE: To evaluate potential sex differences in temporal lobe activation during the performance of a functional magnetic resonance (MR) imaging pass ive-listening paradigm. MATERIALS AND METHODS: Twenty strongly right-handed volunteers (10 men, 10 women) underwent imaging with a 1.5-T machine by using a gradient-echo echo -planar sequence. The task consisted of passive listening to simple narrati ve text interleaved with same-narrative text played backward. Volumes of in terest were drawn around anterior and posterior areas of activation in bila teral temporal lobes. The peak percentage of activation and the percentage of activated voxels at single-voxel significance levels of 10(-2), 10(-3), and 10(-4) within each volume of interest were measured. An asymmetry index A was then calculated for both anterior and posterior-volumes of interest such that A = (L - R)/(L + R), where R is either the peak percentage activa tion or the percentage of activated voxels within the right volume of inter est and L is either the peak percentage activation or the percentage of act ivated voxels within the left volume of interest. The asymmetry indexes wer e compared between men and women by using a standard t test. RESULTS: Men showed a significantly higher degree of asymmetric activation than did women ih both the anterior and posterior volumes of interest by us ing peak percentage activation and at all single-voxel significance levels. The degree df activation asymmetry was greater by using single-voxel signi ficance measurements, compared with peak percentage activation measures. CONCLUSION: Women demonstrate a higher degree of bilateral language represe ntation in temporal lobe regions than do men during passive listening. Thes e findings, combined with the variable results of prior functional MR imagi ng language studies of sex differences, suggest that they may be task speci fic.