Task: Class Definition Understanding (ontology: Human_Society/EmotionOntology)

Which of the following definitions best describes 'circadian sleep/wake cycle, REM sleep'?

A. All sleep stages in the circadian sleep/wake cycle other than REM sleep. These stages are characterized by a slowing of brain waves and other physiological functions.
B. The part of the circadian sleep/wake cycle where the organism is not asleep.
C. The part of the circadian sleep/wake cycle where the organism is asleep.
D. A stage in the circadian sleep cycle during which dreams occur and the body undergoes marked changes including rapid eye movement, loss of reflexes, and increased pulse rate and brain activity.

Answer: A stage in the circadian sleep cycle during which dreams occur and the body undergoes marked changes including rapid eye movement, loss of reflexes, and increased pulse rate and brain activity.