ASYMMETRIC EFFECTS OF OVARIAN HORMONES ON HEMISPHERIC ACTIVITY - EVIDENCE FROM DICHOTIC AND TACHISTOSCOPIC TESTS

Previous studies have suggested a role of endogenously cycling ovarian hormones in the modulation of perceptual asymmetries. In the present investigation, participants were given perceptual asymmetry tests incl uding verbal and nonverbal tachistoscopic and dichotic listening tasks during the menstrual and midluteal phases of the menstrual cycle. Sal ivary levels of estrogen and progesterone were also measured. Analyses of performance on the tachistoscopic tests revealed that left visual field, but not right visual field, accuracy was significantly lower fo r both verbal and nonverbal tasks at the midluteal phase than at the m enstrual phase. Right ear performance on the nonverbal dichotic test w as significantly reduced at the midluteal phase. Results suggest suppr ession of right hemisphere processing areas and possible reduction in callosal transfer efficiency at higher levels of ovarian steroids.