The Cortical Representation of Oculomotor Proprioception

描述（由申请人提供）：我们必须知道一个物体相对于身体在视觉空间中的位置，以便看它，靠近它或远离它，伸手触摸它，抓住它，甚至向它扔东西。视觉信息通过视网膜进入大脑，但由于视网膜在轨道上运动，知道物体在视网膜上的位置并不能自动告诉大脑它在空间中的位置。为了计算物体在空间中的位置，大脑不仅要知道它在视网膜中的位置，还要知道视网膜在空间中的位置。大脑通过来自内耳前庭系统和颈部肌肉传感器的信号知道头部在空间中的位置。在大脑的视觉关联皮层中有一些信号可以报告眼睛在眼眶中的位置，但是这些眼睛位置信息的来源是未知的。一种可能性是，眼睛位置信号的来源是作为运动系统的必然放电而产生的，因为控制眼睛运动的肌肉的信号有一个发出眼睛位置信号的成分。我们之前已经发现了这样一种必然信号，它向皮质神经元报告即将发生的眼动的大小。另一种可能是眼外肌肉中的传感器向大脑发送信号，描述眼睛在眼眶中的位置。猴子和人类的眼外肌有许多传感器，看起来像骨骼肌中的传感器，用来表示肌肉的长度。这些传感器通过丘脑投射到初级体感皮层（SI）的3a区，以及第二体感皮层（Sll）。在非常初步的实验中，我们在3a区和Sll区发现了细胞（通过磁共振成像识别），它们描述了眼睛在眼眶中的位置。这个提议有两个目的：1)表征眼睛位置信号，观察它的动眼力、视觉和注意力特性。2)通过麻醉一只眼的眼眶来确定该信号是否具有本体感受性或衍生性来源。这些实验将深入了解大脑分析感知和行动空间的机制，并将帮助我们理解和设计空间行为缺陷的康复策略，例如中风后发生的涉及顶叶皮层的空间行为缺陷，其中SI和Sll是一个组成部分。

DESCRIPTION (provided by applicant): We have to know where an object is in visual space relative to the body, in order to look at it, move towards it or away from it, reach out and touch it, grasp it, or even throw something at it. Visual information enters the brain via the retina, but because the retina moves in the orbit, knowing where something is on the retina does not automatically tell the brain where it is in space. In order to calculate where something is in space, the brain must know not only where it is in the retina, but where the retina is in space. The brain knows where the head is in space from signals from the vestibular system in the inner ear, and from sensors in the neck muscles. There are signals in the visual association cortex of the brain that report where the eye is in the orbit, but the source of this eye position information is unknown. One possibility is that the source of the eye position signal arises as a corollary discharge from the motor system, because the signal controlling the muscles that move the eye has a component signaling the position of the eye. We have previously discovered such a corollary signal which reports the dimensions of an impending eye movement to cortical neurons. The other possibility is that sensors in the extraocular muscles send a signal to the brain describing the position of the eye in the orbit. Monkey and human extraocular muscles have many sensors which look like the sensors in the skeletal muscles that signal muscle length. These sensors project through the thalamus to area 3a in primary somatosensory cortex (SI), and to the second somatosensory cortex (Sll). In very preliminary experiments we have found cells in both area 3a and Sll (as identified by magnetic resonance imaging) which describe the position of the eye in the orbit. This proposal has two aims: 1) to characterize the eye position signal, looking at its oculomotor, visual, and attentional properties. 2) to determine by anesthetizing the orbit of one eye, if the signal has a proprioceptive or a corollary origin. These experiments will provide insight into the mechanisms by which the brain analyzes space for perception and action, and will help us understand and design rehabilitative strategies for deficits in spatial behavior such as occur after strokes involving the parietal cortex, of which SI and Sll form a component.