Shorter sleep durations in adolescents reduce power density in a wide range of waking electroencephalogram frequencies

Sleep restriction and age effects on waking alpha EEG activity in adolescents

Study Objectives

To understand how sleep need changes across adolescence our laboratory is carrying out a longitudinal dose-response study on the effects of sleep duration on daytime sleepiness and performance. This report focuses on the relation of the waking alpha (8-12 Hz) electroencephalogram (EEG) to prior sleep duration, whether this relation changes with age, and whether decreased waking alpha power is related to changes in daytime sleepiness, vigilance, and executive functioning.

Methods

Study participants (n = 77) entered the study at ages ranging from 9.86 to 13.98 years and were studied annually for 3 years. Each year participants completed each of three time in bed (TIB) conditions (7, 8.5, or 10 h) for four consecutive nights. Waking EEG was recorded on the day following the fourth night.

Results

TIB restriction and resultant sleep loss were associated with reduced alpha power with the effect being stronger for the eyes closed condition. TIB restriction altered the power spectrum within the alpha range by increasing the frequency of maximum alpha power. Alpha power decreased with age, but the effect of TIB restriction did not decrease with age. Reduced alpha power was associated with small but significant increases in subjective and objective sleepiness but was not associated with changes in vigilance or executive functioning.

Conclusions

We interpret the alpha depression following sleep loss as incomplete sleep dependent recuperation that contributes to daytime sleepiness. The absence of a decrease in TIB effects with age indicates that this sleep need measure does not decrease over early to mid-adolescence.

Effects of sleep restriction on the sleep electroencephalogram of adolescents

STUDY OBJECTIVES

This report describes findings from an ongoing longitudinal study of the effects of varied sleep durations on wake and sleep electroencephalogram (EEG) and daytime function in adolescents. Here, we focus on the effects of age and time in bed (TIB) on total sleep time (TST) and nonrapid eye movement (NREM) and rapid eye movement (REM) EEG.

METHODS

We studied 77 participants (41 male) ranging in age from 9.9 to 16.2 years over the 3 years of this study. Each year, participants adhered to each of three different sleep schedules: four consecutive nights of 7, 8.5, or 10 h TIB.

RESULTS

Altering TIB successfully modified TST, which averaged 406, 472 and 530 min on the fourth night of 7, 8.5, and 10 h TIB, respectively. As predicted by homeostatic models, shorter sleep durations produced higher delta power in both NREM and REM although these effects were small. Restricted sleep more substantially reduced alpha power in both NREM and REM sleep. In NREM but not REM sleep, sleep restriction strongly reduced both the all-night accumulation of sigma EEG activity (11-15 Hz energy) and the rate of sigma production (11-15 Hz power).

CONCLUSIONS

The EEG changes in response to TIB reduction are evidence of insufficient sleep recovery. The decrease in sigma activity presumably reflects depressed sleep spindle activity and suggests a manner by which sleep restriction reduces waking cognitive function in adolescents. Our results thus far demonstrate that relatively modest TIB manipulations provide a useful tool for investigating adolescent sleep biology.

A roadmap for development of neuro-oscillations as translational biomarkers for treatment development in neuropsychopharmacology

New treatment development for psychiatric disorders depends critically upon the development of physiological measures that can accurately translate between preclinical animal models and clinical human studies. Such measures can be used both as stratification biomarkers to define pathophysiologically homogeneous patient populations and as target engagement biomarkers to verify similarity of effects across preclinical and clinical intervention. Traditional "time-domain" event-related potentials (ERP) have been used translationally to date but are limited by the significant differences in timing and distribution across rodent, monkey and human studies. By contrast, neuro-oscillatory responses, analyzed within the "time-frequency" domain, are relatively preserved across species permitting more precise translational comparisons. Moreover, neuro-oscillatory responses are increasingly being mapped to local circuit mechanisms and may be useful for investigating effects of both pharmacological and neuromodulatory interventions on excitatory/inhibitory balance. The present paper provides a roadmap for development of neuro-oscillatory responses as translational biomarkers in neuropsychiatric treatment development.