Investigating a dual-pathway framework for praxis

项目摘要 执行熟练的动作依赖于两个基本的能力：模仿动作，以快速学习新的 行为，并使用工具来更有效地操纵我们的环境。模仿和工具的使用至关重要 对于许多日常生活活动;在肢体失用症的临床障碍中这些能力的丧失，经常 在许多神经系统疾病中观察到，包括约50%的左半球卒中患者， 是增加照顾者依赖性和卒中后恢复不良的最强预测因子。尽管公认的 虽然这些能力的重要性，但模仿和工具使用背后的加工机制仍不清楚， 这在很大程度上是由于与研究它们相关的挑战。模仿和工具使用都涉及翻译 概念认知目标（即，知道如何发球）转化为复杂的运动指令集（即， 用球拍准确地击打网球）。因此，模仿和工具使用的研究需要融合许多 认知和运动神经科学的概念。这项提议旨在通过以下方式弥合这种认知运动鸿沟： 提出了一种新的理论，解释了支持模仿和工具使用的共同机制， 概念性的目标实际上变成了运动指令。 该理论建立在我们先前的研究基础上，假设两个相互作用的加工途径：（1）A 根据末端执行器的轨迹指定动作的路线（例如，写信），提供 以抽象（与身体无关）的方式定义期望的工具或手运动的有效手段，以及（2） 路线，指定行动方面的身体配置，提供了一个更详细的，但仍然计算 在整个动作中对整个肢体（和工具）位置的易处理的描述。虽然这两条路线 通常一起工作，但由于任务需求，它们可能在不同程度上参与（例如，专注于球拍 轨迹或肩肘腕位置）或当不同的大脑区域 支持这些不同的处理路线被中断。因此，这两条路线的证据将是 通过健康个体的新型任务转换模式建立，测量行为障碍 由于使用经颅磁刺激对相关脑区域的瞬时破坏，或者通过量化 左半球中风患者的慢性缺陷。我们将应用新的严格的运动学分析， 评估行为，将患者损伤与失用症的临床测量相关联，并使用最近开发的 多变量病变症状映射方法，以确认这些路线的神经解剖学基础。 总之，这些努力将确定和描述轨迹和身体配置规划如何支持 模仿和工具使用行为的生产和感知。结果不仅会促进我们对 失用症，强调替代代偿途径，可能有针对性的康复治疗，但 可以作为更广泛地研究认知运动相互作用的模型。

PROJECT SUMMARY Performing skilled actions relies on two fundamental abilities: imitating movements to quickly learn new behaviors, and using tools to more efficiently manipulate our environments. Imitation and tool use are critical for many activities of daily living; loss of these abilities in the clinical disorder of limb apraxia, frequently observed in many neurological disorders including in ~50% of individuals with left-hemisphere stroke, is the strongest predictor of increased caregiver dependence and poor post-stroke recovery. Despite the recognized importance of these abilities, the processing mechanisms underlying imitation and tool use remain unclear, in large part due to the challenges associated with studying them. Imitation and tool use both involve translating conceptual cognitive goals (i.e., knowing how to serve a tennis ball) into intricate sets of motor commands (i.e., accurately hitting a tennis ball with a racket). Hence, the study of imitation and tool use requires merging many concepts from cognitive and motor neuroscience. This proposal aims to bridge this cognitive-motor divide by developing a new theory of the common mechanisms supporting imitation and tool use that explains how conceptual goals are actually turned into motor commands. The proposed theory builds on our prior research by hypothesizing two interacting processing routes: (1) A route that specifies actions in terms of the trajectory of the end-effector (e.g., writing letters), affording an efficient means of defining desired tool or hand motion in an abstract (body-independent) manner, and (2) A route that specifies actions in terms of body configurations, providing a more detailed but still computationally tractable description of the positioning of the entire limb (and tool) throughout an action. While these two routes typically work together, they may be engaged to different extents due to task demands (e.g., focusing on racket trajectories or shoulder-elbow-wrist positions during a tennis serve) or when the different brain regions supporting these distinct processing routes become disrupted. Thus, evidence of these two routes will be established through novel task-switching paradigms in healthy individuals, measuring behavioral impairments due to transient disruptions of relevant brain regions using transcranial magnetic stimulation, or by quantifying chronic deficits in patients with left-hemisphere strokes. We will apply novel rigorous kinematic analyses to assess behavior, correlate patient impairments with clinical measures of apraxia, and use recently-developed multivariate lesion-symptom mapping approaches to confirm the neuroanatomical bases of these routes. Together, such efforts will identify and characterize how trajectory and body-configuration planning support the production and perception of imitation and tool use actions. Results will not only advance our understanding of apraxia, highlighting alternative compensatory pathways that might be targeted for rehabilitation treatment, but serves as a model for studying cognitive-motor interactions more broadly.