Abstract
Purpose: :
When grating patterns moving in opposite directions are presented to each eye dichoptically, alternating monocular periods of movement in opposite direction are perceived; binocular rivalry (BR). During BR dominant eye always follows the motion stimulus. However, it is not known whether the suppressed eye is responsive to motion stimulus during BR. Our purpose was to study the effect of BR suppression on early ocular following responses (OFR).
Methods: :
Dichoptic stimuli were established using a mirror haploscope with two computer monitors which subtend 40 x 30 deg at 47 cm from each eye. Stationary horizontal grating pattern for right eye and vertical for left eye were presented to subjects to generate BR. Psychophysical duration and frequency of BR alternation with stationary stimuli was recorded by taking subject’s input from a push–button. In eye movement paradigm, the stationary orthogonal stimuli were the same. Subjects pressed a button to trigger an onset of brief horizontal movement (750 ms) of vertical gratings and an offset of stationary horizontal gratings as soon as there was a perception of a vertical or horizontal grating during BR. Eye movements were recorded using an infrared eye tracking system. All data were analyzed off–line.
Results: :
The duration of BR alternations were consistent with a Gamma distribution. The latencies of early OFR in the psychophysical suppressed phase were significantly longer than in both the psychophysical dominant phase and monocular condition. Velocities of EM’s in the psychophysical suppressed phase were significantly slower than in the psychophysical dominant phase and monocular condition in an open–loop time window but not in a closed–loop window.
Conclusions: :
OFR are suppressed during the psychophysical suppressed phase of BR in an open–loop window but not in a closed–loop window. Objective measurement of BR suppression using OFR may provide a useful approach for evaluating binocular function.
Keywords: eye movements • binocular vision/stereopsis • ocular motor control