The effect of cycling female estradiol levels on retinal-based smooth pursuit eye movements (SPEM) and post-target offset persistence

Abstract

Estradiol has primarily been associated with the female reproductive system; however, estradiol receptors have been located in the retinas of male and female humans, as well as throughout the central nervous system (CNS) including lower brainstem areas associated with oculomotor functioning. The present study investigated the significance of estradiol in relation to smooth pursuit eye movements (SPEM) with the specific intention of localizing estradiol effects on realtime and on extrapolated SPEM tracking after target termination. This was accomplished in two ways. First, testing occurred at two opposing stages of the female menstrual cycle: the late follicular and the late luteal phases, where estradiol levels are known to be high and low respectively. Second, we selected participants symptomatically categorized into three groups: women who did not have Premenstrual Syndrome (PMS)-type symptoms and who were not using hormonal contraception within the last three months (control group), women who were hormonally sensitive due to the presence of PMS-type symptoms and were not using hormonal contraception (PMS-type group), and women who were using the hormonal contraceptive Alesse™ or the generic form Aviane™ (Alesse™ user group). Horizontal SPEMs were measured using a 60 Hz infrared eye tracker. We found deviations from nominal sinusoidal eye movement patterns between our control, PMStype and Alesse™ user groups in which the hormonally sensitive and regulated groups (PMS-type and Alesse™ users) showed shorter durations of persistence (defined as duration of movement that statistically followed an extrapolated track after target termination), greater amplitude excursions, and a left-to-right excursion bias. These findings suggest that further efforts should be made in order to better understand the modulatory interactions of stable estradiol- or low progesterone-based affective symptoms and their underlying common neural circuitry with SPEM maintenance. The relevant SPEM neural circuitry includes the cerebellar vermis and flocculus, the medial vestibular nucleus, and other areas where estradiol has been reported to exert its effects.