NeuroImage
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Modulation of the blood estrogen level as it occurs during the menstrual cycle has a strong influence on both neuropsychological and neurophysiological parameters. One of currently preferred hypotheses is that the menstrual cycle hormones modulate functional hemispheric lateralization. We examined six male and six female subjects by functional magnetic resonance imaging (fMRI) to image cortical activation patterns associated with cognitive and motor activation to determine whether these changes during the menstrual cycle can be visualized. ⋯ During both neuropsychological tasks blood estrogen level had a profound effect on the size but not on the lateralization or the localization of cortical activation patterns. The female brain under estrogen showed a marked increase in perfusion in cortical areas involved in both cognitive tasks, whereas the hemodynamic effects during the motor tasks were less pronounced. This might be due to differences in neuronal or endothelian receptor concentration, differences in synaptic function, or, most likely, changes in the cerebrovascular anatomy in different cortical regions.