CEREBRAL CORTICAL MECHANISMS FOR EYE MOVEMENTS AND VISUAL ATTENTION

研究人员进行了两条研究路线，以确定大脑皮层是如何 其传出区控制眼球运动和视觉空间 关注 单神经元记录被用来探索机制， 猴子的顶叶皮层分析空间。 以前的实验 这个实验证明顶叶皮层的神经元描述了 以中心为原点的坐标系中的视觉环境 的凝视。 然而，在猴子进行眼跳之前， 进入神经元的感受野 可以刺激神经元，即使它们目前不在视网膜中， 刺激通常可以激发神经元的位置。 这不是 这是由于感受野的非特异性扩大。 而是 当前感受野的兴奋性降低，因为 未来感受野的兴奋性增加。 既兴奋 变化在扫视之前超过150 ms开始开始。 存在两 神经元群体，每个都描述相同的刺激，这表明， 如果刺激仅在简短的时间内闪烁， 扫视前的间隔。 猴子可以准确地扫视 刺激闪烁100 ms，500 ms，然后进行干预眼跳。 如果 刺激闪烁100 ms，在扫视前150 ms开始， 他们会错误定位目标，就好像他们是在平均两个目标， 神经元群体。 单神经元记录被用来分析顶叶皮层是如何被激活的。 猴子参与了视觉注意的潜在过程。 顶叶神经元对闪光刺激的开始有反应， 感受野 若要查看此活动是否与 刺激进入感受野，或由闪光引起的注意 光，开发了一个范例，其中一个圆形八元素阵列 出现并在屏幕上停留10分钟或更长时间。 猴子 他的目光落在了田歌的身上，文龙也跟着盯着她。 出现一个外源性线索，与其中一个符号相匹配， 对稳定阵列中的匹配符号的扫视。 当猴子 使扫视阵列的中心，使一个或多个阵列 在神经元的感受野中， 顶叶皮层没有反应，尽管当刺激出现时， 在感受野中闪现 当提示指示猴子 在对阵列中的刺激进行扫视时，神经元开始 在提示出现后放电，潜伏期长于 然后继续，直到猴子做出反应， 扫视 如果线索出现在感受野， 即使眼跳是对接受者外的目标进行的， 领域 这些结果表明，顶叶神经元既需要 视觉刺激位于神经元的感受野， 猴子注意刺激。 闪烁的刺激不可避免地吸引一些 注意力，所以神经元会对它们做出反应，无论刺激是否 与动物的任务有关。 相反，神经元的反应时， 由于行为操纵，猴子注意到一个目标， 已经进入神经元的感受野，但没有引起反应 因为猴子没有注意到它。

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 the 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 is not due to a nonspecific enlargement of the receptive field. Instead, the excitability of the current receptive field decreases, as the excitability of the future receptive field increases. Both excitability changes begin more than 150 ms before the saccade. The existence of two populations of neurons, each describing the same stimulus, suggests that stimuli should be localized inaccurately if they flash only in the brief interval before a saccade. Monkeys can make accurate saccades to a stimulus flashed for 100 ms, 500 ms before an intervening saccade. If the stimuli are flashed for 100 ms, beginning 150 ms before a saccade, they mislocalize the target, as if they were averaging the two populations of neurons. Single neuron recording was used to analyze how the parietal cortex of the monkey participates in the processes underlying visual attention. Parietal neurons respond to the onset of flashed stimuli in their receptive fields. To see if this activity is related to the entry of the stimulus into the receptive field, or the attention evoked by a flashed light, a paradigm was developed in which a circular eight-element array appeared and remained on the screen for 10 minutes or more. The monkey made a saccade to the center of the array and then was instructed by the appearance of an exogenous cue, which matched one of the symbols, to make a saccade to the matching symbol in the stable array. When the monkey made the saccade to the center of the array, bringing one or more array members into the receptive field of the neuron, many neurons in the parietal cortex did not respond, although they did when the stimulus flashed in the receptive field. When the cue instructed the monkey to make a saccade to the stimulus in the array, the neurons began to discharge after the appearance of the cue with a latency longer than that of a response to a flash and then continued until the monkey made the saccade. If the cue appeared in the receptive field, the neurons discharged even if the saccade was made to a target outside the receptive field. These results suggest that parietal neurons require both that a visual stimulus lie in the receptive field of the neuron and that the monkey attend to the stimulus. Flashed stimuli ineluctably draw some attention, so the neurons respond to them whether or not the stimuli are relevant to the animal's task. Conversely, the neurons respond when, by virtue of a behavioral manipulation, the monkey attends to a target that has been in the neuron's receptive field but has not evoked a response because the monkey did not attend to it.