What are common indicators of REM sleep on an EEG?

The presence of low voltage mixed activity with sawtooth waves clearly characterizes REM sleep in an EEG. During this sleep stage, brain activity is more akin to wakefulness, which is reflected in the low amplitude and mixed frequency of the brain waves. The sawtooth waves specifically, which are most commonly observed in the central and occipital leads, are a hallmark of REM sleep and signify the intense brain activity occurring during this phase, which is associated with vivid dreaming.

In contrast, high amplitude delta waves typically indicate deep sleep (Stage N3) rather than REM sleep, while continuous alpha wave activity is more commonly seen during relaxed wakefulness. A flatline brain activity would indicate a lack of brain activity, which is not characteristic of any sleep stage and is more indicative of a serious medical condition or brain death. Thus, the distinctive low voltage mixed activity and sawtooth waves are the key indicators to identify REM sleep on an EEG.