A category of sleep disorders (also known as parasomnias) that includes sleepwalking and sleep terrors. Most of the symptoms are due to central nervous system (CNS) activation, specifically motor and autonomic discharge. Arousal disorders have several features in common: mental confusion and disorientation, automatic behaviors, nonresponse to external stimuli, difficulty in being fully awakened, and amnesia the following morning. They usually occur in the first third of the sleep period, at the point of transition from stage iv nrem sleep to rem sleep.