School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK; MRC-Versus Arthritis Centre for Musculoskeletal Ageing Research, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK; Centre for Human Brain Health, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
School of Psychology, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK; Centre for Human Brain Health, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
Brain Stimul. 2020 May-Jun;13(3):707-716. doi: 10.1016/j.brs.2020.02.013. Epub 2020 Feb 21.
The cerebellum and primary motor cortex (M1) are crucial to coordinated and accurate movements of the upper limbs. There is also appreciable evidence that these two structures exert somewhat divergent influences upon proximal versus distal upper limb control. Here, we aimed to differentially regulate the contribution of the cerebellum and M1 to proximal and distal effectors during motor adaptation, with transcranial direct current stimulation (tDCS). For this, we employed tasks that promote similar motor demands, but isolate whole arm from hand/finger movements, in order to functionally segregate the hierarchy of upper limb control.
Both young and older adults took part in a visuomotor rotation task; where they adapted to a 60° visuomotor rotation using either a hand-held joystick (requiring finger/hand movements) or a 2D robotic manipulandum (requiring whole-arm reaching movements), while M1, cerebellar or sham tDCS was applied.
We found that cerebellar stimulation improved adaptation performance when arm movements were required to complete the task, while in contrast stimulation of M1 enhanced adaptation during hand and finger movements only. This double-dissociation was replicated in an independent group of older adults, demonstrating that the behaviour remains intact in ageing.
These results suggest that stimulation of distinct motor areas can selectively improve motor adaptation in the proximal and distal upper limb. This also highlights new ways in which tDCS might be best applied to achieve reliable rehabilitation of upper limb motor deficits.
小脑和初级运动皮层（M1）对于上肢的协调和精确运动至关重要。也有大量证据表明，这两个结构对上肢近端和远端的控制有不同的影响。在这里，我们旨在通过经颅直流电刺激（tDCS）来调节小脑和 M1 对运动适应过程中近端和远端效应器的贡献。为此，我们采用了促进类似运动需求的任务，但将整个手臂与手/手指运动分离，以便将上肢控制的层次结构进行功能分离。
年轻和老年成年人都参与了视觉运动旋转任务；在该任务中，他们通过使用手持操纵杆（需要手指/手部运动）或 2D 机器人操纵器（需要整个手臂的伸展运动）适应 60°的视觉运动旋转，同时应用 M1、小脑或假 tDCS。
我们发现，当手臂运动需要完成任务时，小脑刺激可改善适应性能，而相比之下，刺激 M1 仅增强了手和手指运动时的适应性能。这种双重分离在另一组独立的老年成年人中得到了复制，证明这种行为在衰老中仍然存在。
这些结果表明，刺激不同的运动区域可以选择性地改善上肢近端和远端的运动适应。这也突出了 tDCS 可以以新的方式应用，以实现上肢运动缺陷的可靠康复。
