Neurons are firing at different times. A person is sleepy, already sleeping, or in a sleep transition. It can be observed in from the hippocampus. Theta rhythm is also observed in REM sleep. Therefore, the activity is synchronized.
Waves are large and slow.
Spontaneus, intermitent, high voltage peaks that appear simultaneously in the pontine structures, the lateral geniculate and occipital cortex. Both electrophysiological and neurochemical studies have exploited this phenomenon in an effort to identify the pontine structures involved in this phasic response and also to map their central pathways. The time spent in REM sleep is represented by a light-blue bar. The amount of stage 2 slow-wave sleep increases progressively until it completely occupies the slow waves period toward the end of the night.