Fukushima Kikuro, Fukushima Junko, Warabi Tateo
Faculty of Health Sciences, Hokkaido University Sapporo, Japan.
Front Neurol. 2011 Dec 14;2:78. doi: 10.3389/fneur.2011.00078. eCollection 2011.
Smooth-pursuit eye movements are voluntary responses to small slow-moving objects in the fronto-parallel plane. They evolved in primates, who possess high-acuity foveae, to ensure clear vision about the moving target. The primate frontal cortex contains two smooth-pursuit related areas; the caudal part of the frontal eye fields (FEF) and the supplementary eye fields (SEF). Both areas receive vestibular inputs. We review functional differences between the two areas in smooth-pursuit. Most FEF pursuit neurons signal pursuit parameters such as eye velocity and gaze-velocity, and are involved in canceling the vestibulo-ocular reflex by linear addition of vestibular and smooth-pursuit responses. In contrast, gaze-velocity signals are rarely represented in the SEF. Most FEF pursuit neurons receive neck velocity inputs, while discharge modulation during pursuit and trunk-on-head rotation adds linearly. Linear addition also occurs between neck velocity responses and vestibular responses during head-on-trunk rotation in a task-dependent manner. During cross-axis pursuit-vestibular interactions, vestibular signals effectively initiate predictive pursuit eye movements. Most FEF pursuit neurons discharge during the interaction training after the onset of pursuit eye velocity, making their involvement unlikely in the initial stages of generating predictive pursuit. Comparison of representative signals in the two areas and the results of chemical inactivation during a memory-based smooth-pursuit task indicate they have different roles; the SEF plans smooth-pursuit including working memory of motion-direction, whereas the caudal FEF generates motor commands for pursuit eye movements. Patients with idiopathic Parkinson's disease were asked to perform this task, since impaired smooth-pursuit and visual working memory deficit during cognitive tasks have been reported in most patients. Preliminary results suggested specific roles of the basal ganglia in memory-based smooth-pursuit.
平稳跟踪眼球运动是对额状平行平面内缓慢移动的小物体的自主反应。它们在具有高敏锐度中央凹的灵长类动物中进化而来，以确保对移动目标的清晰视觉。灵长类动物的额叶皮质包含两个与平稳跟踪相关的区域；额叶眼区（FEF）的尾部和辅助眼区（SEF）。这两个区域都接收前庭输入。我们综述了这两个区域在平稳跟踪方面的功能差异。大多数FEF跟踪神经元发出诸如眼球速度和注视速度等跟踪参数的信号，并通过将前庭反应和平稳跟踪反应线性相加来参与抵消前庭眼反射。相比之下，注视速度信号在SEF中很少出现。大多数FEF跟踪神经元接收颈部速度输入，而在跟踪和躯干相对于头部旋转期间的放电调制呈线性相加。在头部相对于躯干旋转期间，颈部速度反应和前庭反应之间也以任务依赖的方式发生线性相加。在跨轴跟踪 - 前庭相互作用期间，前庭信号有效地启动预测性跟踪眼球运动。大多数FEF跟踪神经元在跟踪眼球速度开始后的相互作用训练期间放电，这表明它们不太可能参与产生预测性跟踪的初始阶段。在基于记忆的平稳跟踪任务中对这两个区域的代表性信号以及化学失活结果的比较表明它们具有不同的作用；SEF规划平稳跟踪，包括运动方向的工作记忆，而FEF尾部产生跟踪眼球运动的运动指令。要求特发性帕金森病患者执行此任务，因为大多数患者在认知任务期间报告存在平稳跟踪受损和视觉工作记忆缺陷。初步结果表明基底神经节在基于记忆的平稳跟踪中具有特定作用。
