Sleep and the Sleep-Wake Cycle
The defining behavioral characteristics of sleep that are used to identify sleep in many animals are: (i) a species-specific posture; (ii) reduced responsiveness to external stimuli; (iii) rebound after deprivation see .
The assessment of a species-specific posture requires around-the-clock behavioral observations. In most species, sleep will be accompanied by behavioral quiescence. In some species, such as dolphins, sleep verified by electrophysiological recordings has been observed while the animal is behaving.
Variation in responsiveness across putative sleep and wake states can be assessed by quantification of arousal thresholds for standardized tactile, auditory, or other stimuli....