Graded arousal responses in infants: advantages and disadvantages of a low threshold for arousal

To review studies of upper airway protective reflexes and other aspects of arousal from sleep.

Discussion of pertinent physiological studies.

Infant arousal from sleep incorporates two systems. The first comprises a group of periodically occurring reflexes serving cardiorespiratory homeostatic functions as well as providing for several aspects of normal growth and development. The second system is organized to respond to acute threats to survival during sleep. Both systems are integrated in a single arousal network originating in the brainstem. Full arousal occurs as a progression of events occurring sequentially and manifested by various innate motor and cardiovascular responses. During an arousal, rostral progression from brainstem to cortex is retarded by increasing inhibition which serves to decrease cortical arousals thereby preserving the integrity of rapid eye movement and non-rapid eye movement sleep states. Activation of brainstem arousal reflexes alone can cause recovery from obstruction sleep apnea episodes without the need for cortical arousal, a phenomenon more characteristic of infants than adults.