What happens in the brain when we sleep

A night is made 3 to 6 cycles per night. Each one runs approx 90 Minutes and divided 4 phases: Falling asleep, slow-wave sleep (including light slow-wave sleep and deep slow-wave sleep), REM sleep, and latency/wake duration. During this stage of sleep, the brain remains active and reacts in various ways.

1. The brain sinks into a “fog of consciousness.”

During the day, the hypothalamus, a small region located in the heart of the brain, secretes Serotonin and small proteins “hypnosis” which inhibits neurons of the excitatory system. They help you sleep at night. Eyelids become heavy, eyes sting, yawning increases and Thoughts get confused : This is what scientists call the “fog of consciousness”. Signs that we are going to sleep. Dr. of the Neuroscience Research Center of Lyon. Helen Bastuji’s team analyzed the different brain waves that occur sequentially in the brain during sleep that reflect the activity of neurons using intracranial electrodes. These researchers showed that the thalamus (located above the hypothalamus) The cortex falls asleep firstheadquarters ConsciousnessAnd some can explain Hallucination or sensations felt (Free fall, shock) when sleepy.

2. It slows down more and more

In the second phase of the sleep cycle, “During slow-wave sleep (50-60% of the night), brain electrical activity Slows down gradually explains us Dr. Mark Ray, neurologist and president of the National Institute of Sleep and Vigilance (INSV). Then the sleeper is half asleep and can Wake up easily. In the deep slow-wave sleep phase (20% of the night), the brain’s electrical activity slows down even more, “until reaching 1 Hz While normally, when we are in a quiet waking state, the brain has electrical activity with a frequency of 8 to 12 Hz. Our interlocutor continues. Breathing and heartbeat are regular. It is at this moment that we Especially secretes growth hormone. The sleeper sinks into a state where his brain is increasingly sensitive to external stimuli such as noise or light. He wakes up with difficulty.

3. The brain produces incoherent and complex dreams

In the third phase of the cycle, “During paradoxical sleep (20% at night) The electrical activity of the brain is close to waking when we sleep Brain waves are fast. From the brain’s point of view, the sleeper rarely sleeps and “wakes up” easily. Practically, he is asleep and his muscles are paralyzed.” Describes an expert. This is why this phase is called “contradictory” sleep because the person presents simultaneously Signs of deep sleep and signs of wakefulness. “Many areas of the brain are highly activeLike the visual areas, the emotional areas… on the other hand, the “executive control” areas, active when awake, are inactive there” Dr Philippe Beaulieu, Somnologist. During paradoxical sleep,Those most productive, abundant, pictorial, inconsistent and complex dreams happens. Dream content during REM sleep “Translate the emotional struggles of the moment symbolically“, A somnologist explains.

4. When you wake up, the brain slowly reactivates

At the end of the night, the cycle consists almost exclusively of contralateral sleep. This is whyLucid dreams“Or feel more concrete More in early morning. Daylight or outside noise slowly reactivates the brain and must transition from sleep to consciousness. During this time, it’s possible (and normal) to feel a little off upset and confused. “A kind of sleep stiffness or“Sleep intoxication“, image by Dr. Andrew McHill, director of the Sleep, Chronobiology and Health Laboratory at Oregon Health & Science University.