Department of Neuroscience, Brown University, Providence, Rhode Island, USA.
J Neurophysiol. 2011 Apr;105(4):1603-19. doi: 10.1152/jn.00532.2010. Epub 2011 Jan 27.
A prominent feature of motor cortex field potentials during movement is a distinctive low-frequency local field potential (lf-LFP) (<4 Hz), referred to as the movement event-related potential (mEP). The lf-LFP appears to be a global signal related to regional synaptic input, but its relationship to nearby output signaled by single unit spiking activity (SUA) or to movement remains to be established. Previous studies comparing information in primary motor cortex (MI) lf-LFPs and SUA in the context of planar reaching tasks concluded that lf-LFPs have more information than spikes about movement. However, the relative performance of these signals was based on a small number of simultaneously recorded channels and units, or for data averaged across sessions, which could miss information of larger-scale spiking populations. Here, we simultaneously recorded LFPs and SUA from two 96-microelectrode arrays implanted in two major motor cortical areas, MI and ventral premotor (PMv), while monkeys freely reached for and grasped objects swinging in front of them. We compared arm end point and grip aperture kinematics' decoding accuracy for lf-LFP and SUA ensembles. The results show that lf-LFPs provide enough information to reconstruct kinematics in both areas with little difference in decoding performance between MI and PMv. Individual lf-LFP channels often provided more accurate decoding of single kinematic variables than any one single unit. However, the decoding performance of the best single unit among the large population usually exceeded that of the best single lf-LFP channel. Furthermore, ensembles of SUA outperformed the pool of lf-LFP channels, in disagreement with the previously reported superiority of lf-LFP decoding. Decoding results suggest that information in lf-LFPs recorded from intracortical arrays may allow the reconstruction of reach and grasp for real-time neuroprosthetic applications, thus potentially supplementing the ability to decode these same features from spiking populations.
运动时运动皮层场电位的一个突出特征是独特的低频局部场电位（lf-LFP）（<4 Hz），称为运动事件相关电位（mEP）。lf-LFP 似乎是与区域突触输入相关的全局信号，但它与通过单个单位尖峰活动（SUA）或运动发出的附近输出的关系尚未确定。先前在平面到达任务背景下比较初级运动皮层（MI）lf-LFPs 和 SUA 中的信息的研究得出结论，lf-LFPs 比尖峰在运动方面具有更多信息。然而，这些信号的相对性能基于同时记录的通道和单位的数量较少，或者是针对跨会话平均的数据，这可能会错过更大规模的尖峰群体的信息。在这里，我们同时记录了两个 96 微电极阵列在两个主要运动皮层区域 MI 和腹侧运动前区（PMv）中的 LFPs 和 SUA，而猴子自由地到达并抓住在他们面前摆动的物体。我们比较了末端和抓握开口运动学的 lf-LFP 和 SUA 集合的解码准确性。结果表明，lf-LFPs 提供了足够的信息来重建两个区域的运动学，MI 和 PMv 之间的解码性能差异很小。个别 lf-LFP 通道通常比任何一个单个单元提供更准确的单个运动学变量的解码。然而，在大量单元中最好的单个单元的解码性能通常超过了最好的单个 lf-LFP 通道。此外，SUA 集合的性能优于 lf-LFP 通道的集合，这与之前报道的 lf-LFP 解码优势不一致。解码结果表明，从皮质内阵列记录的 lf-LFPs 中的信息可能允许实时神经假体应用程序的重建到达和抓握，从而潜在地补充从尖峰群体解码这些相同特征的能力。
