Brain noise contains unique signature of dream sleep

Dream or REM sleep is distinguished by rapid eye movement and absence of muscle tone, but electroencephalogram (EEG) recordings are indistinguishable from those of an awake brain. Neuroscientists have now found an EEG signature of REM sleep, allowing scientists for the first time to distinguish dreaming from wakefulness through brain activity alone. This could help in determining the prognosis for coma patients, and allow study of the impact of anesthesia on dreaming. Source