Sing Helen C, Kautz Mary A, Thorne David R, Hall Stanley W, Redmond Daniel P, Johnson Dagny E, Warren Kimberly, Bailey Joshua, Russo Michael B
Walter Reed Army Institute of Research, Division of Psychiatry & Neuroscience, Silver Spring, MD 20910-7500, USA.
Aviat Space Environ Med. 2005 Jul;76(7 Suppl):C114-35.
High-frequency EEG (HFE) as a potential predictor of alertness/drowsiness was first proposed by Kaplan and Loparo. Sampling EEG at 950 Hz, they established an HFE bandwidth of interest ranging from 100-475 Hz. We extend their work by applying discrete Fourier transform (DFT) of HFE signals sampled at 1000 Hz and partitioned into spectral bands along specific frequency ranges for the assessment of sleep-wake state transition, sleep, and active cognitive engagement.
There were 13 volunteers (6 men, 7 women, 30 +/- 3 yr) who participated in a 40-h sleep-deprivation study, during which time they performed multiple cognitive tasks. EEG, in synchrony with other physiological signals, was collected at a sampling rate of 1000 Hz. EEG and task performance results from two volunteers are discussed in this preliminary analysis of the C3-C4 region data. Spectral components obtained from DFT are delineated into five main frequency bands: low, (LFB, 1-15 Hz); intermediate (IFB, 16-50 Hz); and 3 high frequency bands: HFB1 (51-100 Hz); HFB2 (101-200 Hz); and HFB3 (201-500 Hz) for analysis purposes.
LFB in the 1-15 Hz range at 0.40 spectrum proportion indicated declining alertness; LFB above 0.50 signals transition to sleep; and LFB at 0.70 indicates Stage 2/3 sleep. HFB3 in the 201-500 Hz range at 0.25 and above was a marker of cognitive function and/or capacity.
HFE may provide a quantitative measure of cognitive function capacity. LFB may provide a measure for awake, asleep, or awake-sleep transition, and HFB3 an estimate of cognitive task engagement. HFE may be applied for electroencephalographic monitoring of cognitive performance.
高频脑电图（HFE）作为警觉性/嗜睡的潜在预测指标最早由卡普兰和洛帕罗提出。他们以950赫兹的频率采样脑电图，确定了一个100 - 475赫兹的感兴趣的HFE带宽。我们通过对以1000赫兹采样的HFE信号应用离散傅里叶变换（DFT）并将其沿特定频率范围划分为频谱带，以评估睡眠 - 觉醒状态转换、睡眠和积极的认知参与，从而扩展了他们的工作。
有13名志愿者（6名男性，7名女性，30±3岁）参与了一项40小时的睡眠剥夺研究，在此期间他们执行了多项认知任务。脑电图与其他生理信号同步，以1000赫兹的采样率采集。在对C3 - C4区域数据的初步分析中讨论了两名志愿者的脑电图和任务表现结果。从DFT获得的频谱成分被划分为五个主要频段：低频（LFB，1 - 15赫兹）；中频（IFB，16 - 50赫兹）；以及三个高频段：HFB1（51 - 100赫兹）；HFB2（101 - 200赫兹）；和HFB3（201 - 500赫兹）用于分析目的。
在1 - 15赫兹范围内，频谱比例为0.40时的LFB表明警觉性下降；LFB高于0.50表明向睡眠过渡；LFB为0.70表明处于2/3期睡眠。在201 - 500赫兹范围内，频谱比例在0.25及以上的HFB3是认知功能和/或能力的一个标志。
HFE可能提供一种认知功能能力的定量测量方法。LFB可能提供一种用于清醒、睡眠或清醒 - 睡眠转换的测量方法，而HFB3可用于估计认知任务参与情况。HFE可应用于认知表现的脑电图监测。
