A canonical microcircuitry for visuomotor transformations in the primate brain

为了执行以目标为导向的动作，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肌肉的运动命令，最终执行动作。在灵长类动物中，以前的研究发现了一种复杂的电路，用于将视觉信号转换为特定类型的运动动作，即凝视转移到空间中的物体上。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，这些神经元横跨所谓的动眼神经网络的几个大脑区域，即顶内外侧(LIP)、额叶眼场(FEF)、补充眼场(SEF)以及最近的FEF前面的8A区。该提案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大脑区域中是连续发生的，并且这种转换受皮质组织的两个基本原则支配：a)皮质柱内的垂直加工，其跨过灰质厚度遵循单向偏向(从上层到下层：视觉到运动)，以及b)相邻柱之间的水平加工，主要是在皮质浅层(II和III)。我们进一步假设，水平加工是由一组兴奋性锥体神经元介导的，这些神经元通过抑制性中间神经元(例如，小蛋白细胞)相互作用。当有多个刺激可用时，这种动力学对于选择目标物进行凝视转移是关键。这些计算的结果随后被传递到颗粒下层(V-VI)，在那里锥体神经元将“运动”命令发送到下一个处理阶段(例如，皮质区下游或上丘)。我们将通过记录常见绒猴(Challitrix Jacchus)不同皮质层LIP和FEF区神经元的反应来验证这一假设，这些神经元执行需要将视觉信号转换为凝视命令的任务。我们将使用由多个触点组成的线性探测器，这些触点通过大脑导航技术植入大脑皮质的整个深度，并确定皮质柱内、皮质柱之间和不同区域之间的视觉运动处理是如何发生的。这一结果将揭示灵长类动物大脑中凝视的视觉运动转换的回路和机制。

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.