Hybrid dedicated and distributed coding in PMd/M1 provides separation and interaction of bilateral arm signals.
Hybrid dedicated and distributed coding in PMd/M1 provides separation and interaction of bilateral arm signals.
复制标题
在PMD/M1中的混合专用和分布式编码提供了双边臂信号的分离和相互作用。
DOI：
10.1371/journal.pcbi.1009615
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发表时间：
2021-11
影响因子：
4.3
通讯作者：
Carmena JM
中科院分区：
文献类型：
--
作者：
Dixon TC;Merrick CM;Wallis JD;Ivry RB;Carmena JM
在准备和执行单手运动期间，在运动皮层的两个半球中观察到明显的活动。双半球信号的组织原理及其在整个运动规划中所发挥的功能仍不清楚。通过对猴子进行指示延迟到达任务，我们确定了跨越 PMd 和 M1 的群体反应中的两个组成部分。在准备过程中，PMd 中出现了一个“专用”组件，它将各个单元级别的活动分开。当 M1 强烈参与运动时，它在运动后最为突出，并且主要涉及对侧半球。与最近的报告相反，这些专用信号仅解释了手臂特定神经子空间的分歧。另一个“分布式”组件混合了单元内每个臂的信号，并且包含它的子空间在任何阶段都不会区分臂之间的信号。人口反应的统计数据表明皮质网络有两个功能方面：一个横跨两个半球，用于支持准备和正在进行的过程，另一个主要位于对侧半球并指定单边输出。大脑的运动皮层主要控制身体的另一侧，但在任一手臂的运动过程中经常观察到该区域的神经活动。为了理解这些信号的功能意义，我们必须首先描述它们在神经网络中的组织方式。是否存在单臂独有的活动模式？是否还有其他反映共享功能的模式？重要的是，随着运动计划的制定和执行，这些功能可能会随着时间的推移而改变。在这项研究中，我们分析了运动皮层中单个神经元的反应，并对它们在整个群体中的协同活动模式进行了建模，以表征区分左臂和右臂使用的变化。在任务的准备和执行阶段，我们发现信号逐渐变得更加隔离。尽管许多神经元与任一手臂相关的调节，但那些更专用于单个（通常是对侧）肢体的神经元造成了不成比例的大量差异。然而，也存在较弱的活动模式，在任何阶段都无法区分这两个手臂。这些结果揭示了运动皮层的异质性，突出了到达信号的独立和交互成分。
Pronounced activity is observed in both hemispheres of the motor cortex during preparation and execution of unimanual movements. The organizational principles of bi-hemispheric signals and the functions they serve throughout motor planning remain unclear. Using an instructed-delay reaching task in monkeys, we identified two components in population responses spanning PMd and M1. A “dedicated” component, which segregated activity at the level of individual units, emerged in PMd during preparation. It was most prominent following movement when M1 became strongly engaged, and principally involved the contralateral hemisphere. In contrast to recent reports, these dedicated signals solely accounted for divergence of arm-specific neural subspaces. The other “distributed” component mixed signals for each arm within units, and the subspace containing it did not discriminate between arms at any stage. The statistics of the population response suggest two functional aspects of the cortical network: one that spans both hemispheres for supporting preparatory and ongoing processes, and another that is predominantly housed in the contralateral hemisphere and specifies unilateral output. The motor cortex of the brain primarily controls the opposite side of the body, yet neural activity in this area is often observed during movements of either arm. To understand the functional significance of these signals we must first characterize how they are organized across the neural network. Are there patterns of activity that are unique to a single arm? Are there other patterns that reflect shared functions? Importantly, these features may change across time as motor plans are developed and executed. In this study, we analyzed the responses of individual neurons in the motor cortex and modeled their patterns of co-activity across the population to characterize the changes that distinguish left and right arm use. Across preparation and execution phases of the task, we found that signals became gradually more segregated. Despite many neurons modulating in association with either arm, those that were more dedicated to a single (typically contralateral) limb accounted for a disproportionately large amount of the variance. However, there were also weaker patterns of activity that did not distinguish between the two arms at any stage. These results reveal a heterogeneity in the motor cortex that highlights both independent and interactive components of reaching signals.