Center for Biomedical Imaging and Neuromodulation, Nathan S. Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd, Orangeburg, NY 10962, USA.
Department of Psychiatry, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA.
Cereb Cortex. 2024 Aug 1;34(8). doi: 10.1093/cercor/bhae338.
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.
高频（>60 Hz）神经电信号可能具有与低频（<30 Hz）信号不同的功能作用。虽然高伽马活动（>60 Hz）并不简单地等同于神经元放电，但它们高度相关，具有相似的信息编码。高伽马活动通常被认为是宽带的，与感觉刺激的相位锁定较差，因此通常在转换为绝对幅度或频谱功率后进行分析。然而，这些分析丢弃了信号极性，从而影响了对本质上是偶极子的神经电事件的解释。在听觉皮层的场电位的频谱时变图中，我们展示了与声音起始不锁相的高频频谱峰值，这些峰值紧随锁相起始反应的宽带峰值。分离构成高频峰值的信号分量揭示了窄带高频振荡事件，其瞬时频率从>150 Hz 快速变化到 60 Hz，这可能是以前报告中的宽带高频谱峰值的基础。分离活动的层幅度分布有两个峰值位置，而层相位模式显示出这些峰值之间的反相关系，表明偶极子的形成。我们的发现表明，非锁相 HGA 的产生部分是由于听觉皮层中颗粒上层神经元集合的振荡或周期性活动。
