Cortical Representation of Mechanical Problem Solving in Tool Use

熟练而准确地操作工具的能力已经成为现代人类生活中不可或缺的组成部分。由于失用症，神经科患者经常表现出使用工具的缺陷。除了缺乏工具功能和工具操作方面的知识外，机械问题解决(MPS)方面的缺陷似乎也是导致工具使用失用的重要原因。如果使用以前未知的工具来实现机械目标，了解对象的物理和机械属性尤其重要。然而，在与熟悉的工具互动时，MPS似乎也是一个重要的认知成分。评估MPS的范例多种多样，但基本的皮质表现还远不清楚。因此，拟议项目的中心目标是使用已建立的行为范式和两种互补的脑成像技术，以更好地了解神经组织和神经网络的基本组件。我们计划使用“新颖工具测试”(NTT)，要求用户选择一个新工具，并使用它通过从工具和对象的结构进行推理来操作对象。我们计划在功能磁共振成像(FMRI)期间检查健康参与者的NTT的执行情况，使用先前研究中建立的一种设置，该设置能够在MRI环境中实际执行手动作(“工具旋转木马”)。这种设计将允许我们区分行动的计划和执行，我们计划测试两只手，以便更好地分析神经表示的侧向性。以前对常见工具使用的功能磁共振研究表明，左侧的额颞顶网络被激活。此外，主要的视觉和感觉运动区也起了作用。我们希望找到相同的激活加上MPS特定的额外模式。在新工具中进行选择可能会激活枕颞区。对于选择和切除，我们预计在左侧顶下小叶和顶上小叶以及左侧缘上回都会有强烈的激活，激活程度因情况而异。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，如先前的fMRI实验所揭示的那样。在刺激这些区域后，我们预计健康参与者的行为减少从视频评分和运动学分析中明显可见。我们假设在选择新工具的过程中，反应时间延长，执行速度变慢。对于使用条件，我们还预计TMS刺激特定脑区会导致更高的运动变异性和更低的运动流畅性。我们的研究将促进对MPS在工具使用中的神经机制的理解，这是使人类能够迅速和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.