Strategy of eye-head coordination for better dynamic visual acuity

为了探讨头部旋转时眼-头协调对动态视力的贡献，我进行了以下两个实验。实验一：要求正常受试者(n=84)阅读并回答3个数字，这些数字按随机顺序呈现。在CRT显示器上，数字在自愿向右旋转时右移90度/S。共进行了30次实验，以正确答案的数量(满分；3 x 30=90)作为DVA评分。DVA得分的平均值和标准差分别为37.0和7.8。实验二：6名正常受试者重复上述实验两周。三名受试者每天进行125次试验(HT组)，另外三名受试者每天进行25次试验(LT组)。DVA评分由治疗前的39.7分提高到治疗后的50.3分。同样，LT组由41.3升至52.3。然而，DVA训练后自主头部运动的变化完全取决于受试者组。虽然LT组的峰值头速从62.1deg/S下降到30.1deg/S，但HT组的峰值速度明显增加了43.3deg/S至79.0deg/S。LT组的策略似乎是合理的，因为在这种头部条件下，左眼运动被认为是由VOR引起的，这干扰了对运动目标的跟踪。HT集团的战略是怎样的？HT组受试者OZ的数据给了我一个很大的提示。他的头部旋转可以提前开始，因此当运动目标出现时处于减速阶段。因此，我认为向左加速引起向右眼球运动就是VOR。我把这个想法命名为“反转VOR假说”。根据这一假说，向右的VOR和向右的追逐产生了向右的高速凝视速度。事实上，受试者OZ表现出80°/S的右视速度，这不能用单纯的追逐眼动来解释，这一“反转VOR假说”为更好地训练DVA提供了可能性。

To investigate the contribution of eye-head coordination for dynamic visual acuity (DVA) during head rotation, I performed following two experiments.Experiment I : Normal subjects (n=84) were asked to read and answer 3 numerals, presented sequentially at random order. The numerals moved rightward at 90 deg/s on a CRT monitor during voluntary rightward rotation. Thirty trials were carried out and numbers of correct answers (full score ; 3 x 30 = 90) were evaluated as DVA score. Mean and SD of their DVA score was 37.0 and 7.8.Experiment II : Six normal subjects repeated the same trial as above for two weeks. Three subjects conducted 125 trials a day (HT group) and another three ones did 25 trials a day (LT group). DVA score in HT group increased from 39.7 to 50.3. Similarly, that in LT group increased from 41.3 to 52.3. The changes of voluntary head motion followed by DVA training, however, completely depended on the subject group. Although the peak head velocity in LT group decreased from 62.1 to 30.1 deg/s, that in HT group apparently increased 43.3 to 79.0 deg/s. The strategy of LT group seems to be reasonable because in this head condition leftward eye movements are thought to be evoked by VOR, which disturbs tracking a moving target. How is the strategy of HT group? Data of subject OZ in HT group gave me a big hint. His head rotation could make an early start and was consequently in deceleration stage when a moving target appeared. Therefore, I considered that leftward acceleration evoked rightward eye movements as VOR. I named this idea "reversal VOR hypothesis". According this hypothesis, rightward VOR and rightward pursuit made a high-speed rightward gaze velocity. Indeed, subject OZ showed 80 deg/s rightward gaze velocity, which can not be explained by only pursuit eye movements.This "reversal VOR hypothesis" holds the possibility of making effective training way for better DVA.