Abstract
Despite the existence of female sex-steroid receptors throughout the CNS, little is known about the non-reproductive effects of cycling sex steroids. Given the convergent evidence for depressive and reproductive cyclic influences on behaviors related to oculomotor physiology (e.g., Braff et al., 2001; Wichniak, et al., 2000) we measured automatic smooth pursuit eye movements (SPEM) in women (pro)retrospectively screened with PMS symptoms (N=23), as non-symptomatic controls (N=23) or as controls using monophasic contraceptives (N=16). SPEM measurements were taken during the participants' late-follicular (LF) and late-luteal (LL) menstrual phase (estradiol & progesterone levels were assessed by salivary immunoenzymometric assay). Horizontal, sinusoidal tracking was done with a 60-Hz infrared eye tracker coupled to a 200-Hz CRT. A 2°-dia "yellow" dot (89 cd/m2) was superimposed on a 23-cd/m2 gray background. Target excursion was ±13.3° from fixation with peak velocity at center. Five target frequencies (0.25 to 2.0 Hz) were presented in ascending order. Eye position and gain (ocular : target peak velocity) were averaged across five cycles. Outside of main frequency effects, we noted an interaction of menstrual cycle phase and group based on five sampled sine wave positions (0° - 360°). A series of independent samples t-tests revealed a significant increase in left-to-right amplitude with lower gain for PMS women tracking the 0.25 and 0.50 Hz target. There were no significant positional errors or saccadic intrusions, nor open-loop volitional initiation differences. Only low-frequency, automatic foveated maintenance SPEM appeared to be affected by a unique, stable estradiol-level PMS cycle. This finding points away from retinotopic or craniotopic dysregulation and focuses more on brainstem operations. Whether or not estradiol specifically modulates diffuse brainstem oculomotor circuits remains unclear; but at least with regards to PMS, it appears that behavioral tracking differences can be manifested through changes (or lack of changes) in steroid levels across the menstrual cycle.
Meeting abstract presented at VSS 2014