Babeş-Bolyai University, Faculty of Physics, RO-400084 Cluj-Napoca, Str. Kogălniceanu Nr. 1, Romania.
Surrey Sleep Research Centre, Faculty of Health and Medical Sciences, University of Surrey, Guildford, UK.
J Neurosci Methods. 2019 Mar 15;316:22-34. doi: 10.1016/j.jneumeth.2018.12.002. Epub 2018 Dec 17.
It has previously been reported that EEG sigma (10-15 Hz) activity during sleep exhibits infraslow oscillations (ISO) with a period of 50 s. However, a detailed analysis of the ISO of individually identified sleep spindles is not available.
We investigated basic properties of ISO during baseline sleep of 34 healthy young human participants using new and established methods. The analyses focused on fast sleep spindle and sigma activity (13-15 Hz) in NREM stage 2 and slow wave sleep (SWS). To describe ISO in sigma activity we analyzed power of power of the EEG signal. For the study of ISO in sleep spindle activity we applied a new method in which the EEG signal was reduced to a spindle on/off binary square signal. Its spectral properties were contrasted to that of a square signal wherein the same spindles and also the inter spindle intervals were permutated randomly. This approach was validated using surrogate data with imposed ISO modulation.
We confirm the existence of ISO in sigma activity albeit with a frequency below the previously reported 0.02 Hz. These ISO are most prominent in the high sigma band and over the centro-parieto-occipital regions. A similar modulation is present in spindle activity. ISO in sleep spindles are most prominent in the centro-parieto-occipital regions, left hemisphere and second half of the night independent of the number of spindles.
The comparison of spectral properties of binary event signals and permutated event signals is effective in detecting slow oscillatory phenomena.
先前有报道称，睡眠期间的脑电图 sigma（10-15 Hz）活动表现出具有 50 s 周期的亚慢波振荡（ISO）。然而，对于单独识别的睡眠纺锤波的 ISO 的详细分析尚不可用。
我们使用新的和已建立的方法研究了 34 名健康年轻的人类参与者在基线睡眠期间 ISO 的基本特性。分析集中在 NREM 阶段 2 和慢波睡眠（SWS）中的快睡眠纺锤波和 sigma 活动（13-15 Hz）上。为了描述 sigma 活动中的 ISO，我们分析了 EEG 信号的功率。对于睡眠纺锤波活动中的 ISO 研究，我们应用了一种新方法，其中 EEG 信号被简化为一个纺锤波开/关二进制方波信号。其频谱特性与方波信号进行了对比，其中相同的纺锤波和纺锤波之间的间隔也被随机置换。这种方法使用施加 ISO 调制的替代数据进行了验证。
我们确认了 sigma 活动中 ISO 的存在，尽管频率低于先前报道的 0.02 Hz。这些 ISO 在高 sigma 频段和中顶枕区最为明显。在纺锤波活动中也存在类似的调制。睡眠纺锤波中的 ISO 在中顶枕区、左半球和后半夜间最为明显，与纺锤波的数量无关。
比较二进制事件信号和置换事件信号的频谱特性在检测慢振荡现象方面是有效的。
