A canonical microcircuitry for visuomotor transformations in the primate brain

为了执行目标导向的动作，大脑必须将传达物体在空间中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，以前的研究已经确定了一个复杂的电路，用于将视觉信号转换为特定类型的运动动作，即凝视空间中的物体。几项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，这些神经元跨越所谓的眼球网络的几个大脑区域，外侧顶内（LIP），额眼场（FEF），补充眼场（SEF）以及最近的区域8A，位于FEF之前。该提案的总体目标是揭示这种视觉转换背后的大脑回路的细节。我们假设凝视的视觉转换是连续发生在眼神经网络的不同脑区，并且这种转换受两个基本的皮质组织原则支配：a）皮质柱内的垂直处理，其跨越灰质的厚度，遵循单向偏置（从上层到下层：视觉到运动），和B）主要在表层皮质层（II和III）内的相邻列之间的水平处理。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（例如，小清蛋白细胞）。当多个刺激可用时，这种动态是选择用于注视转移的目标的关键。然后，这些计算的输出被传递到颗粒下层（V-VI），在颗粒下层（V-VI）中，锥体神经元将“运动”命令发送到下一个处理阶段（例如，皮质区下游或上级丘）。我们将测试这一假设，记录在不同的皮质层的区域LIP和FEF的普通绒猴（绒猴jacchus）执行任务，需要将视觉信号转化为凝视命令的神经元的反应。我们将使用由多个触点组成的线性探头，这些触点通过大脑导航技术跨越植入的皮层的整个深度，并确定皮层列内、皮层列之间以及不同区域之间的视觉处理是如何发生的。研究结果将揭示灵长类动物脑中凝视的视觉转换回路和机制。

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.