Sex differences in language processing: functional MRI methodological considerations

PURPOSE: To evaluate the influence of both analysis methods and tasks used in the determination of language related sex differences. Previous neuroimaging studies evaluating sex differences in language processing have been inconsistent. MATERIALS AND METHODS: The current study compared FMRI activation between men and women on a variety of language tasks using different types of individual (laterality and activation volume) and group analyses to evaluate the effects of task and methodology. Forty subjects completed five language tasks, 19 men and 21 women. RESULTS: Group analyses revealed greater activation for men compared with women in the left pars orbitalis while women showed greater activation within the right insula. With individual analyses, there were no significant sex differences in laterality using two large regions of interest (ROIs) covering the inferior frontal and temporoparietal regions; however, there were significant sex effects within small, specific ROIs (insula, middle temporal and pars opercularis, triangularis, and orbitalis). When holding the task constant, some methods (for example different ROIs within individual analyses) revealed sex differences while others methods did not, indicating a dependence on methodology. CONCLUSION: The results partly explain why FMRI studies evaluating language related sex effects have been inconsistent.