Crone N E, Miglioretti D L, Gordon B, Lesser R P
Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Brain. 1998 Dec;121 ( Pt 12):2301-15. doi: 10.1093/brain/121.12.2301.
It has been shown in animals that neuronal activity in the 'gamma band' (>30 Hz) is associated with cortical activation and may play a role in multi-regional and multi-modal integration of cortical processing. Studies of gamma activity in human scalp EEG have typically focused on event-related synchronization (ERS) in the 40 Hz band. To assess further the gamma band ERS further, as an index of cortical activation and as a tool for human functional brain mapping, we recorded subdural electrocorticographic (ECoG) signals in five clinical subjects while they performed visual-motor decision tasks designed to activate the representations of different body parts in sensorimotor cortex. ECoG spectral analysis utilized a mixed-effects analysis of variance model in which within-trial temporal dependencies were accounted for. Taking an exploratory approach, we studied gamma ERS in 10-Hz-wide bands (overlapping by 5 Hz) ranging from 30 to 100 Hz, and compared these findings with changes in the alpha (8-13 Hz) and beta (15-25 Hz) bands. Gamma ERS (observed in three out of subjects) occurred in two broad bands-'low gamma' included the 35-45 and 40-50 Hz bands, and 'high gamma' the 75-85, 80-90, 85-95 and 90-100 Hz bands. The temporal and spatial characteristics of low and high gamma ERS were distinct, suggesting relatively independent neurophysiological mechanisms. Low gamma ERS often began after onset of the motor response and was sustained through much of it, in parallel with event-related desynchronization (ERD) in the alpha band. High gamma ERS often began during, or slightly before, the motor response and was transient, ending well before completion of the motor response. These temporal differences in low and high gamma suggest different functional associations with motor performance. Compared with alpha and beta ERD, the topographical patterns of low and high gamma ERS were more discrete and somatotopically specific and only occurred over contralateral sensorimotor cortex during unilateral limb movements (alpha and beta ERD were also observed ipsilaterally). Maps of sensorimotor function inferred from gamma ERS were consistent with maps generated by cortical electrical stimulation for clinical purposes. In addition, different task conditions in one subject produced consistent differences in both motor response latencies and onset latency of gamma ERS, particularly high gamma ERS. Compared with alpha and beta ERD, the topography of gamma ERS is more consistent with traditional maps of sensorimotor functional anatomy. In addition, gamma ERS may provide complementary information about cortical neurophysiology that is useful for mapping brain function in humans.
动物实验表明，“γ频段”（>30Hz）的神经元活动与皮层激活相关，可能在皮层处理的多区域和多模态整合中发挥作用。对人类头皮脑电图γ活动的研究通常集中在40Hz频段的事件相关同步化（ERS）上。为了进一步评估γ频段ERS，作为皮层激活的指标和人类功能性脑图谱绘制的工具，我们记录了5名临床受试者在执行视觉运动决策任务时的硬膜下皮层脑电图（ECoG）信号，这些任务旨在激活感觉运动皮层中不同身体部位的表征。ECoG频谱分析采用了方差分析的混合效应模型，其中考虑了试验内的时间依赖性。采用探索性方法，我们研究了30至100Hz范围内10Hz宽带（重叠5Hz）的γERS，并将这些结果与α（8 - 13Hz）和β（15 - 25Hz）频段的变化进行了比较。γERS（在三名受试者中观察到）出现在两个宽带中——“低γ”包括35 - 45Hz和40 - 50Hz频段，“高γ”包括75 - 85Hz、80 - 90Hz、85 - 95Hz和90 - 100Hz频段。低γ和高γERS的时间和空间特征不同，表明神经生理机制相对独立。低γERS通常在运动反应开始后出现，并在大部分运动反应过程中持续，同时α频段出现事件相关去同步化（ERD）。高γERS通常在运动反应期间或稍前开始，且是短暂的，在运动反应完成前就结束。低γ和高γ在时间上的差异表明它们与运动表现有不同的功能关联。与α和β ERD相比，低γ和高γERS的地形模式更离散且具有躯体定位特异性，仅在单侧肢体运动时出现在对侧感觉运动皮层上（α和β ERD在同侧也有观察到）。从γERS推断出的感觉运动功能图谱与临床皮层电刺激生成的图谱一致。此外，一名受试者在不同任务条件下，运动反应潜伏期和γERS起始潜伏期，特别是高γERS，都产生了一致的差异。与α和β ERD相比，γERS的地形与感觉运动功能解剖学的传统图谱更一致。此外，γERS可能提供有关皮层神经生理学的补充信息，这对于绘制人类脑功能图谱很有用。
