Joshi Anand C, Thurtell Matthew J, Walker Mark F, Serra Alessandro, Leigh R John
Department of Biomedical Engineering, Daroff-Dell'Osso Laboratory, Veterans Affairs Medical Center and University Hospitals, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, Ohio 44106-5040, USA.
J Neurophysiol. 2009 Jul;102(1):513-22. doi: 10.1152/jn.00045.2009. Epub 2009 May 20.
The human ocular following response (OFR) is a preattentive, short-latency visual-field-holding mechanism, which is enhanced if the moving stimulus is applied in the wake of a saccade. Since most natural gaze shifts incorporate both saccadic and vergence components, we asked whether the OFR was also enhanced during vergence. Ten subjects viewed vertically moving sine-wave gratings on a video monitor at 45 cm that had a temporal frequency of 16.7 Hz, contrast of 32%, and spatial frequency of 0.17, 0.27, or 0.44 cycle/deg. In Fixation/OFR experiments, subjects fixed on a white central dot on the video monitor, which disappeared at the beginning of each trial, just as the sinusoidal grating started moving up or down. We measured the change in eye position in the 70- to 150-ms open-loop interval following stimulus onset. Group mean downward responses were larger (0.14 degrees) and made at shorter latency (85 ms) than upward responses (0.10 degrees and 96 ms). The direction of eye drifts during control trials, when gratings remained stationary, was unrelated to the prior response. During vergence/OFR experiments, subjects switched their fixation point between the white dot at 45 cm and a red spot at 15 cm, cued by the disappearance of one target and appearance of the other. When horizontal vergence velocity exceeded 15 degrees/s, motion of sinusoidal gratings commenced and elicited the vertical OFR. Subjects showed significantly (P<0.001) larger OFR when the moving stimulus was presented during convergence (group mean increase of 46%) or divergence (group mean increase of 36%) compared with following fixation. Since gaze shifts between near and far are common during natural activities, we postulate that the increase of OFR during vergence movements reflects enhancement of early cortical motion processing, which serves to stabilize the visual field as the eyes approach their new fixation point.
人类的眼跟踪反应（OFR）是一种前注意、短潜伏期的视野保持机制，如果在扫视之后施加移动刺激，该机制会增强。由于大多数自然的注视转移都包含扫视和聚散成分，我们研究了在聚散过程中OFR是否也会增强。10名受试者在距离为45厘米的视频监视器上观看垂直移动的正弦波光栅，其时间频率为16.7赫兹，对比度为32%，空间频率为0.17、0.27或0.44周/度。在注视/OFR实验中，受试者注视视频监视器上的白色中心点，每次试验开始时该点消失，与此同时正弦波光栅开始向上或向下移动。我们测量了刺激开始后70至150毫秒开环间隔内的眼位变化。向下反应的组均值（0.14度）比向上反应（0.10度和96毫秒）更大，潜伏期更短（85毫秒）。在对照试验中，当光栅保持静止时，眼漂移的方向与先前的反应无关。在聚散/OFR实验中，受试者在45厘米处的白点和15厘米处的红点之间切换注视点，由一个目标的消失和另一个目标的出现作为提示。当水平聚散速度超过15度/秒时，正弦波光栅开始移动并引发垂直OFR。与注视后相比，当在集合（组均值增加46%）或散开（组均值增加36%）过程中呈现移动刺激时，受试者的OFR显著增大（P<0.001）。由于在自然活动中远近之间的注视转移很常见，我们推测在聚散运动期间OFR的增加反映了早期皮质运动处理的增强，这有助于在眼睛接近新的注视点时稳定视野。
