Institut de Neurosciences Cognitives de la Méditerranée, CNRS-Aix-Marseille University, France.
Cereb Cortex. 2012 Sep;22(9):2148-59. doi: 10.1093/cercor/bhr299. Epub 2011 Oct 20.
The local field potential (LFP) is a population measure, mainly reflecting local synaptic activity. Beta oscillations (12-40 Hz) occur in motor cortical LFPs, but their functional relevance remains controversial. Power modulation studies have related beta oscillations to a "resting" motor cortex, postural maintenance, attention, sensorimotor binding and planning. Frequency modulations were largely overlooked. We here describe context-related beta frequency modulations in motor cortical LFPs. Two monkeys performed a reaching task with 2 delays. The first delay demanded attention in time in expectation of the visual spatial cue, whereas the second delay involved visuomotor integration and movement preparation. The frequency in 2 beta bands (around 20 and 30 Hz) was systematically 2-5 Hz lower during cue expectancy than during visuomotor integration and preparation. Furthermore, the frequency was directionally selective during preparation, with about 3 Hz difference between preferred and nonpreferred directions. Direction decoding with frequency gave similar accuracy as with beta power, and decoding accuracy improved significantly when combining power and frequency, suggesting that frequency might provide an additional signal for brain-machine interfaces. In conclusion, multiple beta bands coexist in motor cortex, and frequency modulations within each band are as behaviorally meaningful as power modulations, reflecting the changing behavioral context and the movement direction during preparation.
局部场电位（LFP）是一种群体测量指标，主要反映局部突触活动。β振荡（12-40Hz）出现在运动皮层的 LFP 中，但它们的功能相关性仍存在争议。功率调制研究将β振荡与“静息”运动皮层、姿势维持、注意力、感觉运动绑定和运动规划联系起来。频率调制在很大程度上被忽视了。我们在这里描述运动皮层 LFP 中与上下文相关的β频率调制。两只猴子执行了一个带有两个延迟的伸展任务。第一个延迟要求在时间上注意，以期待视觉空间线索，而第二个延迟则涉及到视觉运动整合和运动准备。在期望线索时，两个β频带（约 20 和 30Hz）的频率比视觉运动整合和准备时低 2-5Hz。此外，在准备期间，频率具有方向性选择性，首选和非首选方向之间存在约 3Hz 的差异。用频率进行方向解码的准确性与用β功率相同，当将功率和频率结合起来时，解码准确性显著提高，这表明频率可能为脑机接口提供额外的信号。总之，多个β频带共存于运动皮层中，每个频带内的频率调制与功率调制一样具有行为意义，反映了不断变化的行为背景和准备期间的运动方向。
