NTT Communication Science Laboratories, Nippon Telegraph and Telephone Corporation, Atsugi, Kanagawa, Japan.
Institute of Cognitive Neuroscience, University College London, London, United Kingdom.
J Neurophysiol. 2021 Sep 1;126(3):816-826. doi: 10.1152/jn.00134.2021. Epub 2021 Jul 28.
When reaching for an object with the hand, the gaze is usually directed at the target. In a laboratory setting, fixation is strongly maintained at the reach target until the reaching is completed, a phenomenon known as "gaze anchoring." While conventional accounts of such tight eye-hand coordination have often emphasized the internal synergetic linkage between both motor systems, more recent optimal control theories regard motor coordination as the adaptive solution to task requirements. We here investigated to what degree gaze control during reaching is modulated by task demands. We adopted a gaze-anchoring paradigm in which participants had to reach for a target location. During the reach, they additionally had to make a saccadic eye movement to a salient visual cue presented at locations other than the target. We manipulated the task demands by independently changing reward contingencies for saccade reaction time (RT) and reaching accuracy. On average, both saccade RTs and reach error varied systematically with reward condition, with reach accuracy improving when the saccade was delayed. The distribution of the saccade RTs showed two types of eye movements: fast saccades with short RTs, and voluntary saccade with longer RTs. Increased reward for high reach accuracy reduced the probability of fast saccades but left their latency unchanged. The results suggest that gaze anchoring acts through a suppression of fast saccades, a mechanism that can be adaptively adjusted to the current task demands. During visually guided reaching, our eyes usually fixate the target and saccades elsewhere are delayed ("gaze anchoring"). We here show that the degree of gaze anchoring is flexibly modulated by the reward contingencies of saccade latency and reach accuracy. Reach error became larger when saccades occurred earlier. These results suggest that early saccades are costly for reaching and the brain modulates inhibitory online coordination from the hand to the eye system depending on task requirements.
当伸手去拿物体时，目光通常会注视目标。在实验室环境中，注视点会强烈地固定在伸手目标上，直到伸手完成，这一现象被称为“注视锚定”。虽然传统的解释通常强调两个运动系统之间的内部协同联系，但最近的最优控制理论将运动协调视为适应任务要求的解决方案。我们在这里研究了在伸手过程中注视控制在多大程度上受到任务要求的调节。我们采用了一种注视锚定范式，参与者必须伸手去够目标位置。在伸手过程中，他们还必须进行扫视眼动，将视线转移到目标位置以外的显著视觉提示上。我们通过独立改变扫视反应时间（RT）和伸手准确性的奖励条件来操纵任务要求。平均而言，扫视 RT 和伸手误差都与奖励条件系统地变化，当扫视延迟时，伸手准确性提高。扫视 RT 的分布显示出两种类型的眼动：快速扫视，RT 较短，以及自愿扫视，RT 较长。增加高伸手准确性的奖励会降低快速扫视的概率，但不会改变其潜伏期。结果表明，注视锚定通过抑制快速扫视来起作用，这种机制可以自适应地调整以适应当前的任务要求。在视觉引导的伸手过程中，我们的眼睛通常会注视目标，而扫视到其他地方的眼睛会被延迟（“注视锚定”）。我们在这里表明，注视锚定的程度可以根据扫视潜伏期和伸手准确性的奖励条件灵活调节。当扫视发生得更早时，伸手误差会变大。这些结果表明，早期扫视对手臂伸展是有代价的，大脑会根据任务要求在线调节从手到眼系统的抑制性协调。
