NEURAL SUBSTRATES FOR CONTROL OF REACHING IN HUMANS

这个项目的目标是定位人类目标导向到达的神经基质。使用15-O正电子发射断层扫描（PET）的功能性脑映射将用于成像正常人类志愿者的任务相关区域脑血流量（rCBF）的变化，并使用经颅磁刺激（TMS）来可逆地破坏受试者执行各种目标到达任务的选定皮质区域的功能。虽然运动学习的基础已经被详细地描绘出来，但对在线纠错、长期感觉运动适应以及视觉和动觉控制信号的协调的基础却知之甚少。有三个具体的目标，对应的问题：具体目标1：描绘各自的神经基质的视觉和运动控制的目标到达。三个实验将解决这一问题，每个实验都有一组单独的受试者（每个实验10名受试者），使用分离视觉和动觉目标和轨迹控制的目标到达范式。实验1.1:PET研究视觉与动觉的瞄准和到达的引导。实验1.2：在线纠错过程中视觉引导与动觉引导的PET研究。实验1.3:PET对棱镜适应过程中视觉与动觉轨迹引导的研究。具体目标2：确定在线错误纠正和运动错误诱导的感觉运动适应的神经基础。计划进行四个实验，每个实验将涉及一套目标到达范式，以分离在线错误纠正和运动错误诱导的感觉运动适应。实验2.1：在线误差校正与运动误差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和眼动成分的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：经颅磁刺激研究后顶叶对在线错误纠正的贡献：显性与阈下目标位移以及到达轨迹的视觉与动觉引导。具体目标3：确定目标指向到达过程中知觉扭曲（感觉错配和参照错配）诱导的感觉运动适应的神经基础。计划进行四项实验。每一个都涉及一组有针对性的达到范式，这些范式分离了长期感觉运动适应的三个因素：感觉错配、再参照错配和运动错误。实验3.1：主动与被动棱镜自适应的PET研究。实验3.2：有和无视觉运动误差时棱镜自适应的PET研究。实验3.3：棱镜适应认知因素的PET研究。实验3.4：经颅磁刺激研究侧面前额叶和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.