CEREBRAL CORTICAL MECHANISMS FOR EYE MOVEMENTS AND VISUAL ATTENTION

两条线索被用来确定大脑是如何 皮质及其传出区域控制眼球运动和 视觉空间注意力。 单神经元记录被用来探索通过这种机制 猴子的顶叶皮质分析空间。以前的实验 在这个实验室里证明了顶叶皮质的神经元 描述坐标系中的视觉环境，其原点为 是人们凝视的中心。然而，在猴子进行扫视之前， 将通过以下方式进入神经元感受场的刺激 即将到来的眼跳可以兴奋神经元，即使它们是 目前不在视网膜位置，在那里刺激可以正常 刺激神经元。这种坐标系移动的现象 已经扩展到减缓眼球运动。猴子被训练成 通过平稳的追逐来跟随缓慢移动的视觉刺激，或者 动物旋转时对前庭眼球反射的抑制 以与刺激计划相同的速度。在两种情况下，当眼睛移动时 最近消失的刺激的空间位置进入 神经元的感受野，许多顶神经元放电 尽管当刺激计划闪现时，它并不在他们的 可接受的领域。这种感受场机制现在发生了变化 解释了大脑如何在以下情况下产生空间精确的运动 人类或猴子在其周围环境中移动，而不必 等待视网膜代表在视网膜内重建 眼睛在空间移动后的大脑皮层。 尽管顶叶皮质中的神经元在 视觉引导的眼球运动，目前还不清楚这是否 响应与扫视目标唤起的注意力有关， 或进行扫视的意图。为了区分这一点 有可能，猴子们接受了一项反扫视任务的训练。猴子 开始任务时，先看一个可以是红色的凝视点 或者是绿色的。当注视灯变红时，猴子们随后 进行了一次扫视以获得一个闪光的目标。当凝视灯亮起时 是绿色的，猴子们朝相反的方向快速跳跃 闪光的目标，但与目标的距离相同。这个 大多数顶神经元对视觉刺激是否有反应 它口述了一个朝向或远离它的扫视。几个细胞有反应 刺激，但当相反的刺激指示扫视时 刺激的空间位置。最不常见的细胞类型 只有关于扫视方向的信息。这些数据表明 顶叶皮质的大多数神经元描述了一种视觉 刺激以及人们对这种刺激的关注。几个细胞 唯一地描述运动方向。

Two lines of inquiry were followed to determine how the cerebral cortex and its efferent regions control eye movements and visuospatial attention. Single neuron recording was used to probe the mechanisms whereby the parietal cortex of the monkey analyzes space. Previous experiments in this laboratory demonstrated that neurons in parietal cortex describe the visual environment in a coordinate system whose origin is the center of gaze. Before a monkey makes a saccade, however, stimuli that will enter the receptive field of a neuron by virtue of the impending saccade can excite that neuron even though they are currently not in a retinal location in which stimuli can normally excite the neuron. This phenomenon of the coordinate system shift has been extended to slow eye movements. Monkeys were trained to follow a slowly moving visual stimulus by smooth pursuit, or by suppression of the vestibuloocular reflex when the animal is rotated at the same speed as the stimulus. In both cases when the eye moves the spatial location of a recently vanished stimulus into the receptive field of the neuron, many parietal neurons discharge despite the fact that when the stimulus flashed it was not in their receptive fields. This mechanism of receptive field shifts now explains how the brain can generate spatially accurate movements when a human or monkey moves through its environment, without having to wait for the retinal representation to reestablish itself in the cerebral cortex after the eyes have moved in space. Although neurons in the parietal cortex discharge before visually-guided accadic eye movements, it has not been clear if this response is related to the attention that the saccade target evokes, or the intention to make the saccade. To distinguish between this possibility, monkeys were trained on an anti-saccade task. Monkeys began the task by looking at a fixation spot that could be either red or green. When the fixation light was red, the monkeys subsequently made a saccade to acquire a flashed target. When the fixation light was green, the monkeys made a saccade in the opposite direction from the flashed target, but of the same distance as the target. The majority of parietal neurons responded to the visual stimulus whether it dictated a saccade toward or away from it. A few cells responded to the stimulus but also when an opposite stimulus dictated a saccade to the spatial location of the stimulus. The least common cell type only had information about the saccade direction. These data show that the majority of neurons in the parietal cortex describe a visual stimulus and the attention drawn to that stimulus. Few cells describe movement direction uniquely.