Understanding Action Selection in the Tool Use Network

项目摘要： 工具的熟练使用是人类认知的一个决定性成就，并通过存储特定于工具的动作记忆来实现。许多工具与多个操作相关联，大多数日常任务与多个工具相关联。肢体失用症是一种常见的、致残的、令人困惑的左半球疾病，其特征是在激活和选择任务适当的工具动作方面存在显著缺陷。对于在神经系统完好的大脑中进行这种选择的认知机制和大脑区域，以及这些过程在失用症中是如何出错的，我们知之甚少。在其他几个认知领域，有人建议，适当的反应选择发生通过偏见的竞争，也就是说，优先竞争传入的信息，使适当的反应选择。利用这样的框架的承诺，我们已经开发了一个新的功能神经解剖模型的偏见的竞争在一个特定的左半球工具使用网络。被称为“两个行动系统加”（2AS+），该模型产生可检验的假设的主要原则，决定工具的行动选择，以及他们的缺陷失用症。具体来说，我们假设：1）工具动作之间的竞争受到工具动作表征的等级相似性的影响，主要由左后颞叶皮层（pTC）实现，2）竞争过程的结果受到工具动作表征激活的强度和时间的影响，并取决于左后颞叶皮层和顶叶的动态相互作用，3）结果还受到一种机制的影响，这种机制使竞争偏向于适合目标和背景的工具行为，如左额下回（IFG）及其与边缘上回（SMG）的连接所实现的，以及4）有两种亚型的失用症，其特征在于竞争选择过程中的明显失败：前亚型的特征在于不能适当地解决工具动作竞争，后亚型反映了减弱的竞争。这些假设将使用一些互补的方法与健康和脑损伤的参与者进行测试，包括基于体素的病变症状映射，静息功能连接，功能磁共振成像与多体素模式分析，和眼动追踪。通过指定视觉信息何时以及如何在工具表征中发挥作用，拟议的实验承诺严格约束“具身”认知理论，声称工具自动唤起他们的行动。拟议的研究还将通过将相关结构锚定在认知神经解剖模型中来推进对工具动作的理论理解，阐明动作表征是如何组织和激活的，并提高我们对影响失用症中错误和再学习的机制的理解，并对康复产生影响。

Project Summary: Skilled use of tools is a defining achievement of human cognition, and is enabled by the storage of tool-specific action memories. Many tools are associated with more than one action, and most everyday tasks are associated with more than one tool. Limb apraxia is a common, disabling, and puzzling left-hemisphere disorder characterized by prominent deficits in activating and selecting task-appropriate tool actions. Little is known about the cognitive mechanisms and brain regions enabling such selection in the neurologically intact brain, or how these processes go awry in apraxia. In several other cognitive domains, it has been suggested that appropriate response selection occurs via biased competition—that is, the prioritization of competing incoming information to enable appropriate response selection. Capitalizing on the promise of such frameworks, we have developed a new functional-neuroanatomic model of biased competition in a specific left hemisphere Tool Use network. Called “Two Action Systems Plus” (2AS+), the model generates testable hypotheses about the major principles determining tool action selection, and their deficiencies in apraxia. Specifically, we hypothesize that 1) Competition between tool actions is influenced by the graded similarity of tool action representations, as implemented primarily by the left posterior temporal cortex (pTC), 2) The outcome of the competitive process is affected by the strength and timing of activation of tool action representations, and depends on the dynamic interplay of left pTC and the parietal lobes, 3) Outcome is further influenced by a mechanism that biases competition towards the tool action that is appropriate to goals and context, as implemented by the left inferior frontal gyrus (IFG) and its connections with the supramarginal gyrus (SMG), and 4) There are two subtypes of apraxia characterized by distinct failures in the competitive selection process: an anterior subtype characterized by inability to appropriately resolve tool action competition, and a posterior subtype reflecting weakened competition. These hypotheses will be tested using a number of complementary methods with healthy and brain-lesioned participants, including voxel-based lesion symptom mapping, resting functional connectivity, fMRI with multi-voxel pattern analyses, and eyetracking. By specifying when and how visuomotor information plays a role in tool representations, the proposed experiments promise to critically constrain “embodied” cognition theories claiming that tools automatically evoke their actions. The proposed research will also advance the theoretical understanding of tool action by anchoring relevant constructs in a cognitive-neuroanatomic model, clarify how action representations are organized and activated, and improve our understanding of the mechanisms affecting errors and re-learning in apraxia, with implications for rehabilitation.