PDF(Pubmed)
Abstract：
High-frequency (>60 Hz) neuroelectric signals likely have functional roles distinct from low-frequency (<30 Hz) signals. While high-gamma activity (>60 Hz) does not simply equate to neuronal spiking, they are highly correlated, having similar information encoding. High-gamma activity is typically considered broadband and poorly phase-locked to sensory stimuli and thus is typically analyzed after transformations into absolute amplitude or spectral power. However, those analyses discard signal polarity, compromising the interpretation of neuroelectric events that are essentially dipolar. In the spectrotemporal profiles of field potentials in auditory cortex, we show high-frequency spectral peaks not phase-locked to sound onset, which follow the broadband peak of phase-locked onset responses. Isolating the signal components comprising the high-frequency peaks reveals narrow-band high-frequency oscillatory events, whose instantaneous frequency changes rapidly from >150 to 60 Hz, which may underlie broadband high-frequency spectral peaks in previous reports. The laminar amplitude distributions of the isolated activity had two peak positions, while the laminar phase patterns showed a counterphase relationship between those peaks, indicating the formation of dipoles. Our findings suggest that nonphase-locked HGA arises in part from oscillatory or recurring activity of supragranular-layer neuronal ensembles in auditory cortex.
摘要：
高频(>60Hz)神经电信号可能具有不同于低频(<30Hz)信号的功能作用。虽然高伽马活动（>60Hz）并不简单地等同于神经元尖峰，它们高度相关，具有类似的信息编码。高伽马活性通常被认为是宽带的,并且与感觉刺激的相位锁定不良,因此通常在转换为绝对振幅或频谱功率之后进行分析。然而,这些分析丢弃了信号极性，损害了对本质上是偶极的神经电事件的解释。在听觉皮层场电位的光谱时间分布中，我们显示了高频频谱峰值没有锁相到声音的开始，跟随锁相起始反应的宽带峰值。隔离包括高频峰值的信号分量揭示窄带高频振荡事件，其瞬时频率从>150到60Hz迅速变化，这可能是以前报告中宽带高频频谱峰值的基础。孤立活动的层流振幅分布有两个峰位置，而层状相位图案显示出这些峰之间的反相位关系，指示偶极子的形成。我们的发现表明，非相位锁定的HGA部分是由于听觉皮层中球状层神经元集合的振荡或反复活动而引起的。
