NEURAL SUBSTRATES FOR CONTROL OF REACHING IN HUMANS

这个项目的目标是在人类中定位靶向触觉的神经底物。15-O正电子发射断层扫描(PET)脑功能图将被用来成像正常人志愿者局部脑血流量(RCBF)与任务相关的变化，而经颅磁刺激(TMS)将被用来可逆地扰乱执行各种靶向到达任务的受试者选定皮质区域的功能。虽然运动学习的基础已经有了一些详细的描绘，但关于在线纠错、长期感觉运动适应以及视觉和运动控制信号的协调的基础还知之甚少。与这些问题相对应的有三个具体目标：具体目标1：描述目标性到达的视觉和运动控制各自的神经基础。三个实验将解决这一目标，每个实验都有一组单独的受试者(每个实验10个受试者)，使用将视觉和动觉目标与轨迹控制分离的定向到达范式。实验1.1：视觉和动觉靶向的PET研究和伸展的指导。实验1.2：在线纠错过程中视觉指导与运动指导的PET研究。实验1.3：棱镜适应过程中视觉与运动轨迹引导的PET研究。具体目标2：确定在线纠错和运动错误诱导的运动感觉运动适应的神经底物。计划了四个实验，每个实验都将涉及一套目标到达范式，以分离在线纠错和运动错误诱导的感觉运动适应。实验2.1：在线纠错与运动错误诱导的感觉运动适应的PET研究。实验2.2：运动错误诱导的感觉-运动适应的肢体与眼动成分的PET研究。实验2.3：有意识与潜意识在线纠错的PET研究。实验2.4：TMS研究顶后对在线纠错的贡献：显性与潜在性目标移位以及到达轨迹的视觉与运动指导。具体目标3：确定在靶向到达过程中由知觉扭曲(感觉失配和再传入失配)引起的感觉运动适应的神经基础。计划进行四个实验。每一项都包括一套有针对性的到达范式，这些范式分离了与长期感觉运动适应有关的三个因素：感觉失配、再传入失配和运动错误。实验3.1：主动与被动棱镜适应的PET研究。实验3.2：有和没有视觉运动错误的棱镜适应的PET研究。实验3.3：棱镜适应中认知因素的PET研究。实验3.4：TMS研究侧面前额叶与后顶叶对棱镜适应的影响。

The goal of this project is to localize the neural substrates of target-directed reaching in humans. Functional brain mapping with 15-O positron emission tomography (PET) will be used to image task-related changes in regional cerebral blood flow (rCBF) in normal human volunteers, and transcranial magnetic stimulation (TMS) will be used to reversibly disrupt the functioning of selected cortical areas of subjects performing a variety of targeted reaching tasks. While the substrates of motor learning have been mapped in some detail, much less is known about the substrates of on-line error correction, long-term sensorimotor adaptation, and coordination of visual and kinesthetic control signals. There are three specific aims, corresponding to the issues: Specific Aim 1: To delineate the respective neural substrates for visual versus kinesthetic control of targeted reaching. Three experiments will address this aim, each with a separate group of subjects (10 subjects per experiment), using targeted reaching paradigms that dissociate visual and kinesthetic targeting and trajectory control. Exp. 1.1: PET study of visual versus kinesthetic targeting and guidance of reaching. Exp. 1.2: PET study of visual versus kinesthetic guidance during on-line error correction. Exp. 1.3: PET study of visual versus kinesthetic trajectory guidance during prism adaptation. Specific Aim 2: To identify the neural substrates for on-line error correction and motor error-induced sensorimotor adaptation in targeted reaching. Four experiments are planned and each will involve set of targeted reaching paradigms to dissociate on-line error correction and motor error-induced sensorimotor adaptation. Exp. 2.1: PET study of on-line error correction versus motor error-induced sensorimotor adaptation. Exp. 2.2: PET study of limb versus oculomotor components of motor error-induced sensorimotor adaptation. Exp. 2.3: PET study of conscious versus subliminal on-line error correction. Exp. 2.4: TMS study of posterior parietal contribution to on-line error correction: overt versus subliminal target displacements and visual versus kinesthetic guidance of reaching trajectory. Specific Aim 3: To identify the neural substrates for sensorimotor adaptation induced by perceptual distortions (sensory mismatch and reafference mismatch) during target-directed reaching. Four experiments are planned. Each will involve a set of targeted reaching paradigms that dissociate the three factors implicated in long-term sensorimotor adaptation: sensory mismatch, reafferance mismatch, and motor error. Exp. 3.1: PET study of active versus passive prism adaptation. Exp. 3.2: PET study of prism adaptation with and without visual motor error. Exp. 3.3: PET study of cognitive factors in prism adaptation. Exp. 3.4: TMS study of lateral prefrontal versus posterior parietal effects on prism adaptation.