Effects of blood estrogen level on cortical activation patterns during cognitive activation as measured by functional MRI

Modulation of the blood estrogen level as it occurs during the menstrual cy cle has a strong influence on both neuropsychological and neurophysiologica l parameters. One of currently preferred hypotheses is that the menstrual c ycle hormones modulate functional hemispheric lateralization. We examined s ix male and six female subjects by functional magnetic resonance imaging (f MRI) to image cortical activation patterns associated with cognitive and mo tor activation to determine whether these changes during the menstrual cycl e can be visualized. Female subjects, who did not use oral contraceptives, were scanned twice, once during the menses and once on the 11/12 day of the menstrual cycle. A word-stem-completion task, a mental rotation task and a simple motor task were performed by all subjects. Our data provide evidenc e that the menstrual cycle hormones influence the overall level of cerebral hemodynamics to a much stronger degree than they influence the activation pattern itself. No differences were seen between male subjects and female s ubjects during the low estrogen phase. During both neuropsychological tasks blood estrogen level had a profound effect on the size but not on the late ralization or the localization of cortical activation patterns. The female brain under estrogen showed a marked increase in perfusion in cortical area s involved in both cognitive tasks, whereas the hemodynamic effects during the motor tasks were less pronounced. This might be due to differences in n euronal or endothelian receptor concentration, differences in synaptic func tion, or, most likely, changes in the cerebrovascular anatomy in different cortical regions, (C) 2001 Academic Press.