Late-night presentation of an auditory stimulus phase delays human circadian rhythms

Abstract

Although light is considered the primary entrainer of circadian rhythms in humans, nonphotic stimuli, including exercise and melatonin also phase shift the biological clock. Furthermore, in birds and nonhuman mammals, auditory stimuli are effective zeitgebers. This study investigated whether a nonphotic auditory stimulus phase shifts human circadian rhythms. Ten subjects (5 men and 5 women, ages 18-72, mean age +/- SD, 44.7 +/- 21.4 yr) completed two 4-day laboratory sessions in constant dim light (<20 lux). They received two consecutive presentations of either a 2-h auditory or control stimulus from 0100 to 0300 on the second and third nights (presentation order of the stimulus and control was counterbalanced). Core body temperature (CBT) was collected and stored in 2-min bins throughout the study and salivary melatonin was obtained every 30 min from 1900 to 2330 on the baseline and poststimulus/postcontrol nights. Circadian phase of dim light melatonin onset (DLMO) and of CBT minimum, before and after auditory or control presentation was assessed. The auditory stimulus produced significantly larger phase delays of the circadian melatonin (mean +/- SD, -0.89 +/- 0.40 h vs. -0.27 +/- 0.16 h) and CBT (-1.16 +/- 0.69 h vs. -0.44 +/- 0.27 h) rhythms than the control. Phase changes for the two circadian rhythms also positively correlated, indicating direct effects on the biological clock. In addition, the auditory stimulus significantly decreased fatigue compared with the control. This study is the first demonstration of an auditory stimulus phase-shifting circadian rhythms in humans, with shifts similar in size and direction to those of other nonphotic stimuli presented during the early subjective night. This novel stimulus may be a useful countermeasure to facilitate circadian adaptation after transmeridian travel or shift work.

An arousing, musically enhanced bird song stimulus mediates circadian rhythm phase advances in dim light

“…27), maintained throughout all waking periods following study entry, including during exposure to the musically enhanced bird song and control stimulus. The sessions consisted of one baseline night (night 1), two stimulus/control nights (nights 2 and 3), and one poststimulus/postcontrol night (night 4; Fig.…”

“…During the stimulus session, subjects received a 2-h musically enhanced bird song stimulus (described below) from 0600 to 0800. Presentation conditions were as described previously (27). EEG was monitored online via polysomnography, with a technician present, on the administration mornings of the protocol.…”

“…For all subjects, this was the first time they had participated in a laboratory protocol. This study used a telephone and in-person screening procedure similar to that described previously (27), with identical inclusionary and exclusionary criteria. Subjects maintained a habitual, individualized bedtime and wake time of ϳ8 h for at least 1 wk before each session, verified by sleep logs and daily call-ins at bedtime and upon awakening to an answering machine with a time stamp.…”

“…The present experiment determined whether a musically enhanced bird song stimulus, which produces phase delays in the early subjective night (27), would also phase shift circadian rhythms when presented after core body temperature (CBT) minimum in the early subjective day. To measure putative phase shifts, the circadian phase of dim light melatonin onset (DLMO) and CBT minimum before and after stimulus or control presentation were assessed.…”

Addition of a non-photic component to a light-based mathematical model of the human circadian pacemaker

“…A variety of non-photic stimuli have also been studied in humans, including the effect of carbohydrate-rich meals (Kräuchi et al, 2002), auditory stimuli (Goel 2005), and exercise. Exercise was reported to facilitate phase advances to a 23.67-h sleep-wake cycle by advancing the pacemaker ~1.6 h over 12 cycles, compared to ~0.8 h delays in the nonexercise control group (Miyazaki et al, 2001).…”