Arousals in infants.

Polygraphic studies of stimulus-induced arousals from sleep in young infants have identified a highly consistent sequence of reflex responses occurring during the 2-4 second period prior to full behavioral arousal. The initial responses in this sequence are an augmented breath (sigh) coupled with a sleep startle that is then followed by stereotyped "thrashing" motor activity. Partial arousals, identified by early components of the sequence (a sigh or a sigh plus startle), were frequently elicited. Startles and thrashing activity were identified as having a significant external airway protective function during mild asphyxia induced by covering the infants' nasal and oral airways.