Indexing covert activity within the oculomotor system via recordings of neck muscle activity

人类通过快速改变视线的定向运动来探索他们的视觉环境。在没有头部运动的情况下进行的小扫视运动可以说是人类所做的最好理解的意志运动。然而，由于眼睛嵌套在移动的头部中，眼动系统进化为控制凝视，并且大的凝视移动由眼睛和头部的协调运动引起（凝视=眼在空间=眼在头部+头在空间）。眼-头凝视转移的普遍性、快速性和准确性使其成为理解大脑如何协调多节段运动的模型系统。 我们已经假设，眼动系统允许选择性招聘的头部运动没有注视转移控制神经活动相对于一个高的“凝视”阈值和一个较低的“头”阈值。在这里，我们测试这一假设在人类中，通过检查颈部肌肉记录指数以及隐蔽的眼表计划。颈部肌肉记录避开了头部运动固有的生物力学复杂性，并在逐个试验的基础上提供了神经控制的直接测量。一个目标将是记录颈部肌肉活动的任务，建立了一个反应的选择之间的竞争，因为在这样的任务过程中发展的隐蔽的眼动计划是很好的理解。这样的方法提供了一个机会，比较颈部肌肉活动的估计来自计算模型的隐蔽眼过程。第二种方法是在短暂的经颅磁刺激（TMS）脉冲后检查颈部肌肉活动。我们最近已经证明，颈部肌肉的反应是由额眼场（FEF）的TMS引起的，我们现在希望利用这一发现，通过使用这样的诱发反应作为大的凝视转移的隐蔽计划期间的FEF参与的测定。贯穿本提案项目的共同主题是，人类颈部肌肉活动为开发眼科项目提供了客观的测量，否则这些项目将因凝视轴的稳定性而被视为“隐蔽”。

Humans explore their visual environment through orienting movements that rapidly change their line of sight. Small saccadic eye movements made without head movements are arguably the best understood volitional movement made by humans. However, because the eyes are nested within a mobile head, the oculomotor system evolved to control gaze, and large gaze shifts are brought about by coordinated movements of the eyes and head (gaze = eye-in-space = eye-in-head + head-in-space). The ubiquity, rapidity, and accuracy of eye-head gaze shifts make it a model system for understanding how the brain coordinates multi-segmental motion. We have hypothesized that the oculomotor system permits selective recruitment of head movements without gaze shifts by controlling neural activity relative to a high "gaze" threshold and a lower "head" threshold. Here, we test this hypothesis in humans by examining how well neck muscle recordings index covert oculomotor plans. Neck muscle recordings circumvent the biomechanical complexities inherent to head motion, and provide a direct measure of neural control on a trial-by-trial basis. One aim will be to record neck muscle activity during tasks that set up a competition between response alternatives, as the covert oculomotor plans developing during such tasks are well understood. Such an approach provides an opportunity to compare neck muscle activity with estimates of covert oculomotor processes derived from computational models. A second approach will be to examine neck muscle activity following brief pulses of transcranial magnetic stimulation (TMS). We have recently demonstrated that a neck muscle response is evoked by TMS of the frontal eye fields (FEF), and we now look to leverage this finding by using such evoked responses as an assay of FEF engagement during covert plans for large gaze shifts. The common theme throughout this proposal projects is that neck muscle activity in humans provides an objective measure into developing oculomotor projects that would otherwise be deemed "covert" by virtue of stability of the gaze axis.