Cortical Representation of Mechanical Problem Solving in Tool Use

熟练而精确地操作工具的能力已成为现代人类生活的重要组成部分。由于失用症，神经系统患者经常表现出使用工具的缺陷。除了工具功能和工具操作的知识受损外，机械问题解决（MPS）的缺陷似乎是工具使用失用症的重要原因。如果使用以前未知的工具来实现机械目标，了解物体的物理和机械特性尤为重要。然而，当与熟悉的工具交互时，MPS似乎也是一个重要的认知组成部分。各种各样的范式来评估MPS发展，但潜在的皮层表征远不清楚。因此，拟议项目的中心目标是使用两种互补的脑成像技术建立行为范式，以更好地理解神经组织和神经网络的基本组成部分。我们计划使用“新颖工具测试”（NTT），它要求用户选择一个新颖的工具，并通过从工具和对象的结构中推理来使用它来操作对象。我们计划在功能磁共振成像（fMRI）期间使用先前研究中建立的设置来检查健康参与者的NTT执行情况，该设置可以在MRI环境（“工具旋转木马”）中实际执行手部动作。这种设计将使我们能够区分行动的计划和执行，我们计划测试双手，以便更好地分析神经表征的横向性。以前对熟悉工具使用的功能磁共振成像研究表明，左侧额颞顶叶网络被激活。此外，初级视觉和感觉运动区域也起作用。我们希望找到相同的激活加上额外的模式是MPS特异性的。在新工具中进行选择可能会激活枕颞区。对于选择和执行，我们预计在左侧顶叶下小叶和顶叶上小叶以及左侧旁回有强烈的激活，并且根据不同的条件有明显的激活差异。作为补充方法，我们计划使用相同的设置和经颅磁刺激（TMS）来确定与MPS相关的关键区域的不同功能，正如之前的fMRI实验所揭示的那样。在刺激这些区域后，我们预计从视频评分和运动学分析中可以明显看出健康参与者的行为下降。我们假设在选择新工具的过程中，反应时间延长，执行速度减慢。对于使用条件，我们还期望更高的运动变异性和降低的运动流畅性与TMS刺激特定的大脑区域有关。我们的研究将促进对MPS在工具使用中的神经机制的理解，这是允许人类快速熟练地使用工具的主要先决条件之一。

The ability to operate tools skilfully and precisely has become an essential component of modern human life. Neurological patients often show deficits in using tools due to apraxia. Apart from im-paired knowledge of tool function and tool manipulation, deficits in mechanical problem solving (MPS) seem to contribute significantly to tool use apraxia. Understanding the physical and mechan-ical properties of objects is particularly important, if previously unknown tools are used to achieve a mechanical goal. However, also when interacting with familiar tools, MPS seems to be an important cognitive component. A variety of paradigms to assess MPS evolved, but the underlying cortical representations are far from clear. The central objective of the proposed project is therefore to use an established behav-ioural paradigm with two complementary brain imaging technologies to gain a better understanding of the neural organisation and the essential components of the neural network.We plan to use the “Novel Tool Test” (NTT) that requests users to select a novel tool and use it to manipulate an object by reasoning from the tool’s and object’s structure. We plan to examine the execution of the NTT in healthy participants during functional magnetic resonance imaging (fMRI) using a set-up established in previous studies, which enables actual execution of hand actions in the MRI environment (the “tool carousel”). The design will allow us to distinguish between planning and execution of the action, and we plan to test both hands for a better analysis of the laterality of the neural representation. Former fMRI studies of familiar tools use showed that a left-sided fronto-temporo-parietal network is activated. Moreover, primary visual and sensorimotor areas contribute. We expect to find the same activations plus additional patterns that are MPS specific. Choosing among novel tools presumably activates occipito-temporal areas. For both the selection and execu-tion, we expect strong activations in the left inferior and superior parietal lobule and in the left su-pramarginal gyrus with distinct differences in the activations depending on the condition. As the complementary method, we plan to use the same set-up and transcranial magnetic stimula-tion (TMS) to determine the distinct functions of key areas associated with MPS as revealed by the former fMRI experiment. After stimulation of these areas, we expect behavioural decrements in the healthy participants obvious from video scoring and kinematic analysis. We hypothesize prolonged reaction times and slowed executions during the selection among novel tools. For the use condition, we additionally expect higher movement variability and decreased movement fluency associated with TMS stimulation of specific brain areas.Our studies will foster the understanding of the neural mechanisms of MPS in tool use, which is one of the major prerequisites allowing humans to use tools promptly and skillfully.