Sensory contributions to control of human hand movements: digit representations in higher-order somatic loci and their neural interactions with primary motor cortex

这项拟议的研究将调查人类大脑中处理与手相关的感觉和运动信息的区域。感兴趣区包括初级和次级躯体感觉皮质和内侧顶上小叶。我们的目标是了解这些皮质区域如何代表感觉输入，以及当输入对任务变得重要或指示即将到来的手的运动时，它们的表示如何改变。这些目标将使用两种提供免费信息的非侵入性技术来实现，即功能磁共振成像(FMRI)和成对脉冲经颅磁刺激(TMS)。对于每个感兴趣的区域，功能磁共振成像将被用来确定哪些手指占据了最大的皮质区域，对特定类型的感觉输入的反应有多强烈，以及反应是否增加或减少取决于输入与任务或运动的相关性。利用TMS，将探索每个感兴趣区与初级运动皮质之间的相互作用，初级运动皮质是负责手运动的脊柱路径的最大贡献者。每个感兴趣的皮质区域都与初级运动皮质有直接的投射，但感觉区域何时将其信息传递到初级运动皮质，以及这些信息是如何传达的，都存在不确定性。例如，感觉投射是会减少初级运动皮质的反应，还是会增加反应？了解支持感觉引导手运动的神经机制对于开发旨在改善手功能的疗法至关重要，这些疗法旨在改善中风或运动障碍(如肌张力障碍)患者的手功能。拟议的研究计划将在健康人群中调查感觉-运动手运动的皮质机制，这是开发帮助临床人群的方法的先驱。

The proposed research will investigate the areas of the human brain that process both sensory and movement information related to the hand. The areas of interest include the primary and secondary somatosensory cortex and the medial superior parietal lobule. The goals are to understand how each of these cortical areas represent sensory input, and how their representations change when input becomes important to the task, or dictates an upcoming movement of the hand. The goals will be accomplished using two non-invasive techniques that provide complimentary information, functional magnetic resonance imaging (fMRI) and paired-pulse transcranial magnetic stimulation (TMS). For each area of interest, fMRI will be used to identify which digits occupy the most cortical territory, how intense responses are to specific types of sensory input, and if responses increase or decrease depending on how relevant the input is to the task, or movement. Using TMS, the interaction between each area of interest and the primary motor cortex, the largest contributor to the spinal path responsible for hand movements, will be probed. Each of the cortical areas of interest have direct projections with the primary motor cortex yet there are uncertainties about when the sensory area conveys its information to the primary motor cortex, and how this information is conveyed. For example, will the sensory projection reduce responses in primary motor cortex, or will it increase responses? Understanding the neural mechanisms that underpin sensory-guided hand movements is essential to developing therapies that aim to improve hand function in patients such as those have suffered stroke or with movement disorders such as dystonia. The proposed research program will investigate the cortical mechanisms of sensory-motor hand movement in healthy populations, a precursor to developing methods to assist clinical populations.