Cerebral Asymmetry and Cognitive Performance Show Complementary Fluctuations across the Menstrual Cycle
Geoff Sanders and Deborah Wenmoth
Over the last decade, interest in possible biological influences on neuropsychological development and performance has focused on the possible role of hormones, specifically the gonadal steroids for which two distinct effects have been identified (for reviews, see Becker, Breedlove, & Crews, 1992; Nelson, 1995). During critical prenatal or perinatal periods, gonadal steroids exert permanent organizational effects on brain and behavior ( Collaer & Hines, 1995). In adulthood, these same hormones exert phasic activational effects ( Kimura & Hampson, 1994). One approach to the study of activational effects in humans is to look for potential changes in performance across the menstrual cycle. Such changes have been reported for cognitive performance and functional cerebral asymmetry and it is this relationship that we explore here.
In the review that follows, we shall show that reports of significant changes in functional cerebral asymmetry across the menstrual cycle reveal an inconsistent relationship between maximum asymmetry and point in cycle. However, we shall argue that this inconsistency disappears when direction of hemispheric advantage is considered. Right hemisphere tasks reveal greater asymmetry when estrogen is low, whereas left hemisphere tasks reveal greater asymmetry when estrogen is high. To support this position we describe data obtained from a dichotic listening study in which women performed two tasks at two points in their menstrual cycle. Our left hemisphere verbal task showed greater asymmetry during the midluteal phase, when estrogen is high, while our right hemisphere music task showed greater asymmetry at menses, when