Biomedical Engineering Reference
In-Depth Information
Stage 1 power spectrum for EEG
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Figure 10.10
A normalized power spectrum for a segment of an EEG channel monitoring stage 1 of
NREM sleep.
Stage 2 power spectrum for EEG
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2468 012 14 16 18 20
Figure 10.11
The power spectrum for stage 2 of NREM sleep shows a relative increase in the 12- to
14-Hz range because of sleep spindles.
0
patient enters REM sleep, the sawtooth waves are denoted by the increase in the
theta frequency band (4 to 7 Hz) (Figure 10.13).
10.14.2 EOG
The EOG measures the potential difference between the front and back of the ocular
globe and is able to detect movements of the eyes [45]. The eye movement is an indi-
cation of whether the patient is in the REM sleep stage or NREM sleep. SEMs
appear in stage 1 of NREM sleep and are usually gone by stage 2 of NREM sleep.
NREM stages 3 and 4 do not contain any eye movement. REMs, which appear as
much sharper impulses, show up in wakefulness and REM sleep. Figures 10.14 and
10.15 have been adapted from Geyer et al. [43]. Figure 10.14 shows an example of
slow eye movements in stage 1 of NREM sleep, whereas Figure 10.15 shows exam-
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