Ivana Hromatko

The activational effects of sex hormones on spatial ability have been well documented. It has been suggested that these effects might be related to hormonally induced changes in interhemispheric communication. In this EEG study, we opted to explore menstrual cycle-related changes in the efficacy of solving mental rotation tasks and laterality indices while participants were engaged with the tasks. We compared 2D and 3D mental rotation tasks, as they differ both psychometrically and in terms of lateralization. A group (n = 39) of healthy young women was tested twice, once during the mid-luteal (high estrogen and progesterone) and once during the early follicular (low levels of sex hormones) phase of menstrual cycle. The differences in power within the same frequency band on homologous sites of the left and right hemispheres were then calculated. Participants were faster, more accurate, and showed higher laterality scores when solving 3D mental rotation tasks in the early follicular phase compared to the mid-luteal phase. This indicates a higher lateralization of this specific spatial function when the levels of sex hormones are low. However, for 2D mental rotation tasks, participants showed neither shifts in efficacy nor in hemispheric laterality as a function of the menstrual cycle. This pattern of results provides further support for the notion that fluctuations in sex hormones affect laterality, and consequently, the expression of lateralized cognitive abilities.