Influence of hormonal cycle in women on lateralization of brain activation during performing a mental rotation task

Purpose: Differences in performance or in terms of functional imaging during a spatial task are up to now described with contradicting results: there is evidence that women during mid-luteal phase perform more different than women outside this phase.

Methods and Materials: Functional MRI was performed in 24 female volunteers (within mid-luteal phase of menses, outside and with hormonal contraceptives). Active condition was mental rotation task in a standard-block-design. Second level analyses were performed with uncorrected p-values <0.001 for the known ROIs of this stimulus (BA 6, 7, 8, 19, 39, 40 and 44). Lateralization index was calculated using the equation SRi – SLi/ SRi + SLi for each area.

Results: During mental rotation tests, activation in the above mentioned areas could be revealed in all three groups during performing a mental rotation task. An enhanced lateralization was revealed in women with hormonal contraceptives to the left side, the lateralization was more pronounced during the mid-luteal phase but not only to the left side. BA 19, 39 and 44 were lateralized to the right side in both during mid-luteal and menstrual phase but not under contraceptives. The performance in this test was assessed outside the scanner revealing no significant differences between the groups.

Conclusion: Our results indicate that the hormonal changes over cycle time or contraceptive therapy have influences on the lateralisation of cerebral activity in a cognitive function like mental rotation task.