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

拟议的研究将调查人脑中处理与手相关的感觉和运动信息的区域。 感兴趣的区域包括初级和次级体感皮层以及内侧顶叶上小叶。目标是了解每个皮质区域如何表示感觉输入，以及当输入对任务变得重要或指示即将进行的手部运动时，它们的表示如何变化。这些目标将使用两种提供补充信息的非侵入性技术来实现，即功能性磁共振成像（fMRI）和配对脉冲经颅磁刺激（TMS）。 对于每个感兴趣的区域，功能磁共振成像将用于识别哪些数字占据了最多的皮质区域，对特定类型的感觉输入的反应有多强烈，以及反应是否根据输入与任务或运动的相关程度而增加或减少。 使用 TMS，将探测每个感兴趣区域和初级运动皮层之间的相互作用，初级运动皮层是负责手部运动的脊髓路径的最大贡献者。 每个感兴趣的皮层区域都与初级运动皮层有直接投影，但感觉区域何时将其信息传递到初级运动皮层以及如何传递该信息存在不确定性。 例如，感觉投射会减少初级运动皮层的反应，还是会增加反应？ 了解支撑感觉引导手部运动的神经机制对于开发旨在改善中风患者或肌张力障碍等运动障碍患者手部功能的疗法至关重要。拟议的研究计划将调查健康人群感觉运动手运动的皮层机制，这是开发协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.