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Estradiol-Related Variations in Top-Down and Bottom-Up Processes of Cerebral Lateralization

Objective: Natural fluctuations of sex hormones have been shown to modulate cerebral lateralization in dichotic listening tasks. Two recent studies presented contradictory notions regarding the mechanism of this effect. Specifically, whereas Hjelmervik et al. (2012) suggested that estradiol affects lateralization by enhancing top-down processes, such as cognitive control, Hodgetts, Weis, and Hausmann, (2015) suggested that the effect was attributable to estradiol-related variations in bottom-up aspects of lateralization. Method: The present study used 2 well-established left- and right-lateralized dichotic listening tasks (Grimshaw, Kwasny, Covell, & John, 2003; Grimshaw, Séguin, & Godfrey, 2009; Hugdahl, 1995, 2003), with forced-attention conditions to differentiate between these 2 ideas. Fifty-two naturally cycling women underwent both tasks, during either the menstrual, follicular, or luteal cycle phase. Saliva estradiol and progesterone levels were determined by luminescence immunoassays. Results: The results showed that sex hormones did not affect language lateralization, which may be attributable to the larger degree of lateralization yielded by the task, compared with that shown by Hodgetts et al. (2015). In the emotional prosody task, high levels of estradiol were marginally associated with a reduction in cognitive control, whereas the language task yielded no cycle effects for either top-down or bottom-up processes. Conclusions: In sum, the current study revealed weak support for the idea that estradiol affects top-down control of lateralization, as measured with dichotic listening tasks. Given that the task employed in the present study seemed less cognitively demanding than that used previously, it is suggested that estradiol-related inter- and intraindividual variations in lateralization are small when task demands are low.