Menstrual cycle effects on postural stability but not optokinetic function

We investigated the effects of the menstrual cycle on visual-vestibular int eraction by measuring optokinetic function and postural stability at differ ent phases of the cycle. Menstrual cycle phase had no significant effect on gaze-holding, optokinetic nystagmus slow phase velocity, amplitude or freq uency, circularvection latency or optokinetic afternystagmus frequency, amp litude or duration. While menstrual cycle phase had no significant effect o n anterior-posterior sway, it did significantly affect lateral sway (P < 0. 001), with sway on day 5 significantly greater than on days 12 and 21 (P < 0.05 and 0.01, respectively), and sway on day 25 significantly greater than that on day 21 (P < 0.05). (C) 2001 Published by Elsevier Science Ireland Ltd.