A canonical microcircuitry for visuomotor transformations in the primate brain

为了执行目标导向的动作，大脑必须将传递物体在空间中的位置信息的感觉信号映射为最终执行动作的肌肉的运动命令。在灵长类动物中，先前的研究已经发现了一个复杂的电路，它将视觉信号转化为一种特定类型的运动动作，目光转向空间中的物体。一些研究已经发现了编码视觉信号的神经元，编码运动目标（凝视转移）的神经元，以及编码两种信号混合的神经元，这些信号跨越了所谓的动眼神经网络的几个大脑区域，包括侧顶叶内（LIP）、额眼场（FEF）、辅助眼场（SEF）以及最近的FEF前部的8A区。这项提议的首要目标是揭示这种视觉运动转换背后的大脑回路的细节。我们假设凝视的视觉运动转换在动眼神经网络的不同脑区连续发生，并且这种转换受皮层组织的两个基本原则支配：a)沿单向偏倚（从上层到下层）跨越灰质厚度的皮层柱内的垂直加工；视觉到运动)和b)主要在皮层表层（II和III）内相邻柱之间的水平加工。我们进一步假设水平加工是由兴奋性锥体神经元群介导的，这些神经元群通过抑制性中间神经元（如小白蛋白细胞）相互作用。当有多种刺激时，这种动态是选择注视转移目标的关键。这些计算的输出随后被传递到小颗粒层（V-VI），锥体神经元将“运动”命令发送到下一个处理阶段（例如，皮层下游区域或上丘）。我们将通过记录普通狨猴（challitrix jacchus）在执行需要将视觉信号转换为凝视命令的任务时，不同皮层区域LIP和FEF神经元的反应来验证这一假设。我们将使用由多个触点组成的线性探针，这些触点通过大脑导航技术植入皮层的整个深度，并确定皮层柱内、皮层柱之间和不同区域的视觉运动处理是如何发生的。研究结果将揭示灵长类动物大脑凝视视觉运动转换的电路和机制。

In order to perform goal oriented actions, the brain must map sensory signals conveying information about the position of objects in space into motor commands for the muscles that ultimately execute actions. In primates, previous studies have identified a complex circuit for transforming visual signals into a specific type of motor action, gaze shifts toward objects in space. Several studies have found neurons that encode visual signals, neurons that encode movement goals (gaze shifts), as well as neurons that encode a mix of the two signals across several brain areas of the so called oculomotor network, lateral intraparietal (LIP), Frontal Eye Fields (FEF), Supplementary Eye Fields (SEF) and more recently area 8A, anterior to the FEF. The overarching goal of the proposal is to reveal the details of the brain circuit underlying this visuomotor transformation. We hypothesize that visuomotor transformation for gaze occurs serially in different brain areas of the oculomotor network, and that the transformation is governed by two basic principles of cortical organization: a) vertical processing within cortical columns that span the thickness of the gray matter following a unidirectional bias (from upper layers to lower layers: visual to motor), and b) horizontal processing between neighboring columns mainly within superficial cortical layers (II and III). We further hypothesize that horizontal processing is mediated by groups of excitatory pyramidal neurons that interact via inhibitory interneurons (e.g., Parvalbumin cells). Such dynamics is key for selecting a target for a gaze shift when multiple stimuli are available. The output of these computations is then passed to the infragranular layers (V-VI) where pyramidal neurons send the “motor” commands to the next processing stage (e.g., cortical area downstream or the Superior Colliculus). We will test this hypothesis by recording the responses of neurons in different cortical layer of areas LIP and FEF of common marmosets (challitrix jacchus) performing tasks that require transforming visual signals into gaze commands. We will use linear probes consisting of multiple contacts that span the entire depth of the cortex implanted via brain navigation techniques and determine how visuomotor processing within cortical columns, between cortical columns and across different areas take place. The results will reveal the circuitry and mechanisms of the visuomotor transformation for gaze in the primate brain.