Departments of Biomedical Engineering, Neurological Surgery, and Computer Science, Washington University in St. Louis, St. Louis, Missouri 63130, USA.
J Neurosci. 2011 Feb 9;31(6):2091-100. doi: 10.1523/JNEUROSCI.4722-10.2011.
High-gamma-band (>60 Hz) power changes in cortical electrophysiology are a reliable indicator of focal, event-related cortical activity. Despite discoveries of oscillatory subthreshold and synchronous suprathreshold activity at the cellular level, there is an increasingly popular view that high-gamma-band amplitude changes recorded from cellular ensembles are the result of asynchronous firing activity that yields wideband and uniform power increases. Others have demonstrated independence of power changes in the low- and high-gamma bands, but to date, no studies have shown evidence of any such independence above 60 Hz. Based on nonuniformities in time-frequency analyses of electrocorticographic (ECoG) signals, we hypothesized that induced high-gamma-band (60-500 Hz) power changes are more heterogeneous than currently understood. Using single-word repetition tasks in six human subjects, we showed that functional responsiveness of different ECoG high-gamma sub-bands can discriminate cognitive task (e.g., hearing, reading, speaking) and cortical locations. Power changes in these sub-bands of the high-gamma range are consistently present within single trials and have statistically different time courses within the trial structure. Moreover, when consolidated across all subjects within three task-relevant anatomic regions (sensorimotor, Broca's area, and superior temporal gyrus), these behavior- and location-dependent power changes evidenced nonuniform trends across the population. Together, the independence and nonuniformity of power changes across a broad range of frequencies suggest that a new approach to evaluating high-gamma-band cortical activity is necessary. These findings show that in addition to time and location, frequency is another fundamental dimension of high-gamma dynamics.
高伽马波段（>60 Hz）皮质电生理学中的功率变化是局灶性、与事件相关的皮质活动的可靠指标。尽管在细胞水平上发现了亚阈值和同步超阈值活动的振荡，但越来越多的观点认为，从细胞群体记录到的高伽马波段幅度变化是异步放电活动的结果，产生宽带和均匀的功率增加。其他人已经证明了低伽马波段和高伽马波段的功率变化是独立的，但迄今为止，没有研究表明在 60 Hz 以上存在任何这种独立性的证据。基于脑电（ECoG）信号的时频分析的非均匀性，我们假设诱导的高伽马波段（60-500 Hz）功率变化比目前所理解的更为复杂。在六个人类受试者中使用单字重复任务，我们表明不同 ECoG 高伽马子带的功能响应可以区分认知任务（例如，听觉、阅读、说话）和皮质位置。这些高伽马范围内的子带中的功率变化在单个试验内始终存在，并且在试验结构内具有统计学上不同的时间过程。此外，当在三个与任务相关的解剖区域（感觉运动、布罗卡区和颞上回）中的所有受试者中进行整合时，这些与行为和位置相关的功率变化在整个群体中表现出不均匀的趋势。总之，在广泛的频率范围内，功率变化的独立性和非均匀性表明需要采用新的方法来评估高伽马带皮质活动。这些发现表明，除了时间和位置外，频率是高伽马动力学的另一个基本维度。
