High-frequency EEG as measure of cognitive function capacity: a preliminary report.
BACKGROUND
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Sing
Helen C
HC
Walter Reed Army Institute of Research, Division of Psychiatry & Neuroscience, Silver Spring, MD 20910-7500, USA. helen.sing@na.amedd.army.mil
Kautz
Mary A
MA
Thorne
David R
DR
Hall
Stanley W
SW
Redmond
Daniel P
DP
Johnson
Dagny E
DE
Warren
Kimberly
K
Bailey
Joshua
J
Russo
Michael B
MB
D000328:Adult; D001143:Arousal / Q000502:physiology; D001288:Attention / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D004569:Electroencephalography; D005260:Female; D005583:Fourier Analysis; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D012890:Sleep / Q000502:physiology; D012892:Sleep Deprivation / Q000503:physiopathology; D013647:Task Performance and Analysis; D014796:Visual Perception / Q000502:physiology