Reference frame coding in primate frontal cortex

背景：我们的日常行为包括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在以眼睛为中心的参照系中将进入视网膜的视觉信号映射到相对于身体部位（如头部、身体）的其他参照系中执行的运动动作。这种参考系转换背后的神经机制尚不清楚。我们之前假设额叶的皮质区域，辅助视场（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。目的：本文提出的实验将检验这一假设。这项提议有两个主要目的。首先，研究在注视转移过程中，SEF内的不同神经元是否对不同参照系的视觉和运动信息进行编码，以及这些神经元对参照系编码的时间动态。其次，确定SEF神经元是否对不同的运动系统（即凝视和手臂运动）执行参照系转换。科学方法：我们将在3D中测量警觉（头部不受约束）猴子的眼睛和头部运动，训练它们执行两项不同的任务：a)从注视点向视觉目标转移目光，b)在注视点时通过触摸屏幕发出目标位置的信号。通过分离最初的眼睛、头部和身体指向的方向，并使用植入SEF皮层表面的电极微阵列记录神经元反应，我们将确定两个任务中该区域内神经元激活的参考框架和时间动态。这将揭示参考系转换是否发生在SEF中。意义：这个项目的结果可能与神经运动假肢等快速发展的领域相关，因为它们将提供关于运动动作如何在灵长类动物额叶皮层中编码的见解。我们的结果也可以用来建立视觉运动转换的计算模型，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.