Suppression of sensitivity to surround motion during vergence eye movements

Suppression was investigated psychophysically in three human observers by measuring their loss of sensitivity to brief (20 ms) displacement of horizontal lines during 4° convergence movements. A two-alternative forced-choice procedure was used in which the stimulus was presented either in the first or second amplitude of the displacement pulse, the time of the pulse relative to convergence onset, and the half of the trial in which the stimulus was presented were randomized. The results showed that suppression began about 200 ms before and continued until 350 ms after convergence onset, with maximum loss occurring at 25-125 ms after convergence onset. The maximum sensitivity loss was about 0.25 to 0.30 log units