Committee on Computational Neuroscience, University of Chicago, Chicago, IL, United States of America. Center for Bioelectric Interfaces, National Research University Higher School of Economics, Moscow, Russia.
J Neural Eng. 2020 Aug 17;17(4):046035. doi: 10.1088/1741-2552/ab95ea.
The hand-a complex effector comprising dozens of degrees of freedom of movement-endows us with the ability to flexibly, precisely, and effortlessly interact with objects. The neural signals associated with dexterous hand movements in primary motor cortex (M1) and somatosensory cortex (SC) have received comparatively less attention than have those associated with proximal upper limb control.
To fill this gap, we trained two monkeys to grasp objects varying in size and shape while tracking their hand postures and recording single-unit activity from M1 and SC. We then decoded their hand kinematics across tens of joints from population activity in these areas.
We found that we could accurately decode kinematics with a small number of neural signals and that different cortical fields carry different amounts of information about hand kinematics. In particular, neural signals in rostral M1 led to better performance than did signals in caudal M1, whereas Brodmann's area 3a outperformed areas 1 and 2 in SC. Moreover, decoding performance was higher for joint angles than joint angular velocities, in contrast to what has been found with proximal limb decoders.
We conclude that cortical signals can be used for dexterous hand control in brain machine interface applications and that postural representations in SC may be exploited via intracortical stimulation to close the sensorimotor loop.
手——一个由数十个自由度的运动组成的复杂效应器——使我们能够灵活、精确和轻松地与物体交互。与手部运动相关的神经信号在初级运动皮层（M1）和体感皮层（SC）中的研究相对较少，而与近端上肢控制相关的神经信号则受到了较多的关注。
为了填补这一空白，我们训练了两只猴子在跟踪手部姿势的同时抓取不同大小和形状的物体，并记录 M1 和 SC 中的单个神经元活动。然后，我们从这些区域的群体活动中解码它们的数十个关节的手部运动学。
我们发现，我们可以用少量的神经信号准确地解码运动学，并且不同的皮层区域携带关于手部运动学的不同信息量。特别是，M1 的前区的神经信号比后区的信号表现更好，而 SC 中的布罗德曼 3a 区比 1 区和 2 区表现更好。此外，与近端肢体解码器的结果相反，解码性能对于关节角度优于关节角速度。
我们的结论是，皮质信号可用于脑机接口应用中的灵巧手控制，并且 SC 中的姿势表示可以通过皮层内刺激来利用，以闭合感觉运动回路。
