Quantitative Sleep Monitoring - Quantitative EEG Analysis Methods and Clinical Applications - page 278

ples of rapid movements during REM sleep. The frequency of the eye movements
can also be shown by transforming the EOG channel into the frequency domain
using the Fourier transform. Figure 10.16 shows the resulting power spectrum from
an epoch of EOG recording stage 1 of NREM sleep. The presence of SEMs is indi-
cated by the high spectral values in the lower-frequency ranges. Figure 10.17, which
is the resulting power spectrum from an epoch of EOG recording REM sleep, shows
a decrease in the amount of SEMs; however, no REM activity can be seen in the
resulting spectrum. Epochs of REM sleep exist that do not contain REMs. These are
referred to as tonic REM sleep.

10.14.3 EMG
The EMG measures the potential difference of electrodes placed on the chin, and
indicates the chin's muscle tone [45]. There are high levels of activity when the

Stage 1 power spectrum for LOC

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Figure 10.16 The power spectrum from an epoch of EOG showing stage 1 of NREM sleep. An
increase in the 0 to 2-Hz range is an indicator of slow oscillations.

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Stage REM power spectrum for LOC

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Figure 10.17 The resulting power spectrum from an epoch of EOG taken during REM sleep shows a
decrease in the amount of SEMs (0 to 2-Hz range).

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