Genetic determination of sleep EEG profiles in healthy humans.

The contribution of slow brain oscillations including delta, theta, alpha, and sigma frequencies (0.5-16 Hz) to the sleep electroencephalography (EEG) is finely regulated by circadian and homeostatic influences, and reflects functional aspects of wakefulness and sleep. Accumulating evidence demonstrates that individual sleep EEG patterns in non-rapid-eye-movement (NREM) sleep and rapid-eye-movement (REM) sleep are heritable traits. More specifically, multiple recordings in the same individuals, as well as studies in monozygotic and dizygotic twins suggest that a very high percentage of the robust interindividual variation and the high intraindividual stability of sleep EEG profiles can be explained by genetic factors (> 90% in distinct frequency bands). Still little is known about which genes contribute to different sleep EEG phenotypes in healthy humans. The genetic variations that have been identified to date include functional polymorphisms of the clock gene PER3 and of genes contributing to signal transduction pathways involving adenosine (ADA, ADORA2A), brain-derived neurotrophic factor (BDNF), dopamine (COMT), and prion protein (PRNP). Some of these polymorphisms profoundly modulate sleep EEG profiles; their effects are reviewed here. It is concluded that the search for genetic contributions to slow sleep EEG oscillations constitutes a promising avenue to identify molecular mechanisms underlying sleep-wake regulation in humans.