Reference frame coding in primate frontal cortex

背景：我们的日常行为涉及将视觉信息转化为执行我们动作的肌肉的运动命令。这种视觉到运动的转换需要将进入以眼睛为中心的参考系中的视网膜的视觉信号映射到在相对于身体部分的其他系中执行的运动动作（例如，头部、身体）。这种参照系转换背后的神经机制还没有得到很好的理解。我们以前曾假设，额叶的皮质区，补充眼场（SEF），其中视觉和运动信息共存，执行转换，但这一假设尚未得到验证。答：这里提出的实验将检验这一假设。该提案有两个主要目标。首先，调查是否在凝视转移不同的神经元内的SEF编码的视觉和运动信息在不同的参考帧，以及这些神经元内的参考帧编码的时间动态。第二，为了确定SEF神经元是否为不同的运动系统执行参考系变换（即，凝视和手臂运动）。科学方法：我们将测量警觉（头部不受限制）猴子的3D眼睛和头部运动，这些猴子被训练执行两种不同的任务：a）使目光从固定点转向视觉目标，以及B）通过触摸屏幕同时保持目光在固定点上来发出目标位置的信号。通过分离最初的眼睛，头部和身体的指向方向和记录神经元的反应，使用电极微阵列植入的SEF皮层表面，我们将确定的参考框架和时间动态的神经元激活的区域内的两个任务。这将揭示参考框架转换是否发生在SEF中。重要性：该项目的结果可能与神经运动假体等快速发展的领域有关，因为它们将深入了解灵长类动物额叶皮层中的运动行为是如何编码的。我们的研究结果也可用于建立视觉转换的计算模型，这将有助于理解运动控制的神经基础。

BACKGROUND: Our daily behavior involves the transformation of visual information into motor commands for the muscles that execute our actions. This visual-to-motor transformation requires mapping visual signals entering the retinas in an eye-centered reference frame into motor actions executed in other frames relative to body parts (e.g., head, body). The neural mechanisms underlying such reference frame transformation are not well understood. We have previously hypothesized that a cortical area of the frontal lobe, the Supplementary Eye Fields (SEF), in which visual and motor information coexist, performs the transformation, however this hypothesis has not been tested. OBJECTIVES: The experiments proposed here will test this hypothesis. The proposal has two main aims. First, to investigate whether during gaze shifts different neurons within the SEF encode visual and motor information in different reference frames as well as the temporal dynamics of reference frame coding within these neurons. Second, to determine whether SEF neurons perform reference frame transformations for different motor systems (i.e., gaze and arm movements). SCIENTIFIC APPROACH: We will measure eye and head movements in 3D of alert (head unrestrained) monkeys trained to perform two different tasks: a) to make gaze shifts toward a visual target from a fixation spot, and b) to signal the position of a target by touching a screen while keeping gaze on a fixation spot. By dissociating the initial eye, head and body pointing directions and recording neuronal responses using electrode microarrays implanted on the SEF cortical surface, we will determine the reference frame and temporal dynamic of neuronal activation within the area in both tasks. This should reveal whether reference frame transformations occur in the SEF. SIGNIFICANCE: The results of this project could be relevant to rapidly advancing fields such as neural motor prosthesis, since they will provide insight into how motor actions are encoded in the primate frontal cortex. Our results could also be used to build computational models of visuomotor transformations that will contribute to understanding the neural basis of motor control.