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.