Department of Neurosurgery, Stanford University, Stanford, California, United States of America.
PLoS Comput Biol. 2012;8(9):e1002655. doi: 10.1371/journal.pcbi.1002655. Epub 2012 Sep 6.
The functional significance of electrical rhythms in the mammalian brain remains uncertain. In the motor cortex, the 12-20 Hz beta rhythm is known to transiently decrease in amplitude during movement, and to be altered in many motor diseases. Here we show that the activity of neuronal populations is phase-coupled with the beta rhythm on rapid timescales, and describe how the strength of this relation changes with movement. To investigate the relationship of the beta rhythm to neuronal dynamics, we measured local cortical activity using arrays of subdural electrocorticographic (ECoG) electrodes in human patients performing simple movement tasks. In addition to rhythmic brain processes, ECoG potentials also reveal a spectrally broadband motif that reflects the aggregate neural population activity beneath each electrode. During movement, the amplitude of this broadband motif follows the dynamics of individual fingers, with somatotopically specific responses for different fingers at different sites on the pre-central gyrus. The 12-20 Hz beta rhythm, in contrast, is widespread as well as spatially coherent within sulcal boundaries and decreases in amplitude across the pre- and post-central gyri in a diffuse manner that is not finger-specific. We find that the amplitude of this broadband motif is entrained on the phase of the beta rhythm, as well as rhythms at other frequencies, in peri-central cortex during fixation. During finger movement, the beta phase-entrainment is diminished or eliminated. We suggest that the beta rhythm may be more than a resting rhythm, and that this entrainment may reflect a suppressive mechanism for actively gating motor function.
哺乳动物大脑中电节律的功能意义尚不确定。在运动皮层中，12-20 Hz 的β节律已知在运动过程中振幅会短暂降低，并在许多运动疾病中发生改变。在这里，我们展示了神经元群体的活动在快速时间尺度上与β节律相位耦合，并描述了这种关系如何随运动而变化。为了研究β节律与神经元动力学的关系，我们使用人类患者在执行简单运动任务时的硬膜下脑电描记术（ECoG）电极阵列来测量局部皮质活动。除了有节奏的大脑过程外，ECoG 电势还揭示了一个频谱宽带图案，反映了每个电极下方的神经元群体活动的总和。在运动过程中，这个宽带图案的振幅跟随个体手指的动态，在中央前回的不同部位，不同手指具有特定的躯体感觉反应。相比之下，12-20 Hz 的β节律在中央前回和中央后回的弥漫性降低幅度上是广泛的，并且在空间上是连贯的，而不是特定于手指的。我们发现，在固定期间，在中央旁皮质中，这个宽带图案的振幅在β节律的相位以及其他频率的节律上被锁定。在手指运动期间，β相位锁定被减弱或消除。我们认为，β节律可能不仅仅是一种静止节律，这种锁定可能反映了主动门控运动功能的抑制机制。
