Frontal Cortex Control of Gaze Shifts

注视转移是一个重要的视觉运动过程，涉及眼睛和头部的协调运动，用于学习视觉环境。注视移位不仅涉及移动视线以使视觉目标成中心凹，而且还涉及使头部位置与注视对准以使眼球运动灵活且具有高视敏度。这个过程被认为涉及额叶皮层和脑干的神经网络，以协调连贯的运动。最近，对脑干的研究表明，许多以前被认为是“纯动眼器”的结构实际上控制着眼睛和头部的运动。这些发现对我们目前对额叶皮层中动眼运动控制的理解提出了严重的挑战，即皮层是否像“动眼运动”这个名字所声称的那样单独编码眼球运动，或者凝视（即，眼睛和头部的协调运动），如在上级丘和其他脑干部位。这些假设将大大推进我们对运动控制的理解。由于这些问题尚未得到彻底的调查，部分原因是缺乏令人满意的方法来区分眼睛和头部的贡献，在凝视转移，我们将尝试在拟议的实验中使用的技术，分离的眼睛和头部的凝视的贡献。电微刺激、可逆失活/激活和慢性单单位记录的结果将与预定义的变量相关，从而可以充分阐述每个运动的贡献。在特定目标1下，我们将研究额眼场（FEF）和辅助眼场（SEF）在控制眼睛和头部运动中的作用。根据以往研究的建议和我们的初步发现，FEF和4 SEF是额叶皮层中最相关的动眼区。我们要求：FEF和SEF神经元都产生控制眼睛和头部运动的信号，还是每个区域都产生控制部分运动的单独信号？我们将训练头部不受限制的猴子完成任务，将眼睛和头部的贡献与凝视分开，以评估这些可能性。在具体目标2中，我们将研究在注视变化后保持注视/头部对齐的机制。我们假设，一个新发现的区域附近的SEF参与控制这一过程，唤起头部（而不是眼睛）的运动，以中心的眼睛在轨道上，无论初始的凝视位置在空间中。我们将使用上述技术在拟议的实验中评估这一假设。拟议中的研究不仅将提供有关额叶皮层如何控制注视转移的新信息，而且还将揭示与现在皮层和脑干的神经网络共同控制注视转移有关的重要见解。

Gaze shift is an important visuomoter process involving coordinated movements of the eyes and head for learning about the visual environment. A gaze shift involves not only moving the line of sight to foveate visual targets, but also aligning the head position with the gaze to permit2 flexible oculomotor movements with high visual acuity. This process is thought to involve the neural networks of the frontal cortex and those of the brainstem in order to orchestrate coherent movements. Recently, studies in the brainstem have shown that many of the previously assumed "pure oculomoter" structures in fact control movements of both the eyes and the head. These findings pose serious challenges to our current understanding of oculomoter control in the frontal cortex as to whether t he cortex encodes eye movements alone, as the name "oculomoter" claims, or gaze (i.e., coordinated movements of the eyes and head), as in the superior colliculus and other brainstem sites. Verifying these hypothesis will significantly advance our understanding of movement control. Because these issues have not been thoroughly investigated in part due to a lack of satisfying methodology to differentiate the contribution of eye and head during gaze shifts; we will attempt in the proposed experiments to use techniques that separate the contribution of the eyes and head to gaze. The results of electrical microstimulation, reversible inactivation/activation, and chronic single-unit recording will be related to predefined variables, such that the contribution of each movement can be sufficiently elaborated. Under Specific Aim 1, we will study the function of the frontal eye field (FEF) and the supplementary eye field (SEF) on the control of movements of the eyes and head. Based on suggestions of previous studies and our preliminary findings, the FEF and the4 SEF are the most relevant oculomoter areas in the frontal cortex. We ask: both the FEF and the SEF neurons generate signals that control the movements of both the eyes and head, or does each region generate separate signals that control part of the movements? We will train head-unrestrained monkeys in tasks that separate the contribution of the eyes and head to gaze to assess these possibilities. Under Specific Aim 2, we will study the mechanism of maintaining gaze/head alignment following changes in gaze. We hypothesize that a newly discovered region near the SEF participates in the control of this process by evoking head (not eye) movement to center the eyes in the orbit, irrespective of initial gaze positions in space. We will assess this hypothesis in the proposed experiments using the techniques mentioned above. The proposed studies will not only provide new information about how the frontal cortex controls gaze shifts, but also reveal important insights relating to now the neural networks of the cortex and brainstem together control gaze shifts.