In complex living organisms, the internal clock that modulates the activity phase during the day sunlight, and the night is finely regulated. Sleep is defined as a natural reversible state of unconsciousness and decreased responsiveness to external stimuli with relatively low activity.
It is accepted the hypothesis that the timing of sleep in humans is regulated by two processes:
1) Homeostatic Process S: increased during wakefulness and dissipates during sleep. It is reflected in the duration and quality of sleep.
2) Process C: controlled by the circadian pacemaker which is encompassed with Earth day-night cycles thanks to the melatonin secretion. It restricts sleep to a determined time of the day.
Rest-behavior maintenance is essential for the growth and the nervous system. Sleep loss affects human behavior in a different manner and some persons are more vulnerable to sleep loss than others. Many researches have been conducted to properly understand genetic influences in sleep parameters variability among individuals and the underlying biological mechanisms in sleep associated disorders.
Sleep duration is a regulated process, when sleep is lost there are mechanisms that compensate it by extending subsequent sleep. Another sleep characteristic is sleep depth or sleep intensity, which varies according to the previous waking period duration. Deep sleep is the phase of sleep when the electrical activity delta waves on the brain show a slow frequency, and as much slow are the waves activity deeper is the sleep.
Deep sleep, often referred to as slow-wave sleep (SWS), is fundamental for memory consolidation and involves the incorporation of acquired hippocampal memories into the neocortex brain network for long-term storage.
Here is evaluated a genetic marker located in the ADA gene which encodes for an enzyme involved in adenosine production, a substance that it is accumulated during awake and regulates sleep pressure (need of sleep) and sleep depth.
Gene or region studied