追従眼球運動発現における固視視標のオフセットタイミングの影響

抄録

Initial tracking responses were larger when smooth pursuit eye movements were executed after a steady fixation and the initial fixation target disappeared before the onset of the pursuit target motion (Miura et al. JJP, 55 (Suppl), 2005). To study whether this phenomenon is common in the genesis of visually-guided reflexive ocular behaviors, we observed human ocular following response, a reflexive eye movement elicited by the motion of a wide-field visual stimulus. At the beginning of each trial, a stationary fixation point (placed at the center of the screen) and a stationary random-dot pattern (covering the wide visual field) were presented. The subjects fixated the fixation point and immediately (no-gap condition) or 200 ms after the extinction of the fixation point (gap condition), the random-dot pattern moved briefly at 20 deg/s rightward or leftward for 0.2s, and then turned off. The latency of the ocular following responses elicited by the random-dot pattern motion was not affected by the presence of the gap. In all 3 subjects, the change in eye position during the open-loop period of the ocular following responses was significantly larger under the gap condition than under the no-gap condition. The effect of the gap on the ocular following responses started about 15 ms after the onset of the ocular following responses. This result suggests that the efficacy of visuomotor transmission for ocular following responses was facilitated by the release from the fixation before the onset of the random-dot pattern motion, as was seen in the smooth pursuit initiation. [J Physiol Sci. 2006;56 Suppl:S93]