ONTOGENIC VARIATIONS IN AUDITORY AROUSAL THRESHOLD DURING SLEEP

Developmental variations in auditory arousal thresholds during sleep w ere investigated in four groups of normal male subjects - children, pr eadolescents, adolescents, and young adults. Arousal thresholds were d etermined during NREM and REM sleep for tones presented via earphone i nsert on a single night following two adaptation nights of undisturbed sleep. Age-related relationships were observed for both awakening fre quency and stimulus intensity required to effect awakening, with awake nings occurring more frequently in response to lower stimulus intensit ies with increasing age. Although stimulus intensities required for aw akening were high and statistically equivalent across sleep stages in nonadults, higher intensity stimuli were required in Stage 4 relative to Stage 2 and REM sleep in adults. These results confirm previous obs ervations of marked resistance to awakening during sleep in preadolesc ent children and suggest that processes underlying awakening from slee p undergo systematic modification during ontogenetic development.