It is marked by a burst of electrical activity, known as spindles. According to some researchers, if the person is awakened at this point, he or she will deny having been asleep. This is the period most strongly associated with dreams, marked by the awakened's ability to give a narrative type story. This is the brainwave stage of deep sleep, where the dreams occur. It is considered the most dangerous part of sleep to disturb, as people who do not dream for extended periods of time are prone to waking hallucinations.
Delta sleep is also the time period where a person's body repairs itself.
Reported cases of sleep paralysis are attributed to the person somehow waking up immediately from delta while the body is still responding to hormonal signals for repair. For those who record dreams, this might suggest remembering five significant dream vignettes, if trained to remember dreamings.