Revisiting cortical language and praxis representations in males and females

Although the past few decades have seen numerous researchers questioning the nature of sex differences in cognition, the answers remain surprisingly unclear. For example, there is evidence against the long-standing hypothesis that women have more bilateral language representation than men. Indeed, the nature and extent of sex differences in language representation remain largely controversial. So are potential sex differences in praxis representation. In this study, functional magnetic resonance imaging (fMRI) data obtained from 64 females and 61 males during word generation and tool use pantomime were analyzed. The majority of participants had typically organized functions. Whole-brain activity maps and laterality indices (LIs) from regions of interest (ROIs) were examined, using both voxel count and signal intensity. The fMRI results for the language task indicated significantly different activity only for a small region within the female's left occipital cortex. Additional exploratory statistical analysis revealed some, but weak evidence for significant sex difference in the lateralization of the fusiform gyrus. Meanwhile, the statistical analysis of LIs obtained during the praxis task, as well as the whole-brain activity contrasts suggested no sex differences in praxis representation. Moreover, the results from both tasks did not differ depending on the LI calculation method, despite voxel-count based LIs being consistently larger than those based on signal intensity. In conclusion, this study provides new insights into sex differences in cognitive functions, challenging the long-standing assumptions about their nature and extent.