Have you ever observed that at times you feel very tired when you wake up from sleep? Do you know why we don’t remember what happened while others claim that we were talking while sleeping? Today let us explore the mysterious work our brain does while we are asleep.
Before that we need a tool to see inside our brain. Let us take help of the EEG (electroencephalogram). It is a machine that can help monitor the brain activity by measuring the brain waves. Then what are brain waves?
Our day to day activities are governed by our brain. This is possible because of the neurons present in our brain. These neurons (nerve cells) constantly communicate with each other using electrical signals. These electrical signals (also called brain waves) are of different frequencies. Accordingly they are named delta (1-3 Hz), theta (4-7 Hz), alpha (8-12 Hz), beta (13 – 38 Hz) and gamma (39 – 42 Hz) for different frequency bands. These different bands of signals also called EEG waves / Berger waves appear in different stages of our everyday activities. Their appearances also differ from person to person. For example, person with learning disabilities have excessive theta and sometimes alpha waves. Our day to day activities are governed by our brain. This is possible because of the neurons present in our brain. These neurons (nerve cells) constantly communicate with each other using electrical signals. These electrical signals (also called brain waves) are of different frequencies. Accordingly they are named delta (1-3 Hz), theta (4-7 Hz), alpha (8-12 Hz), beta (13 – 38 Hz) and gamma (39 – 42 Hz) for different frequency bands. These different bands of signals also called EEG waves / Berger waves appear in different stages of our everyday activities. Their appearances also differ from person to person. For example, person with learning disabilities have excessive theta and sometimes alpha waves.
When we are in deep sleep, the brain produces delta waves. Theta waves are generated when we start daydreaming or just before falling asleep. These are produced when we are used to the way of doing an everyday work like combing. The alpha waves are produced during meditating or just after completing a work. They are produced in a state of relaxation and it helps in improving our memory. Beta waves are generated when the brain is actively engaged in mental activities like concentrating on studies or giving a speech. When we are intensely focused in solving a problem then gamma waves are produced.
Now you might be tempted to know if we can produce such waves in our brain in order to top the exam. I would not demotivate you because research is going on in this field and we will soon see success in this area.
Coming back to sleep, let us first know that the whole process of sleeping involves various stages of sleep and different brain waves are produced in different stages. One sleep cycle continues around 90 minutes. This means when we sleep at night we complete the sleep cycle around 4 times.
The stages of sleep cycle can be divided into two parts – NREM (Non rapid eye movement) sleep stage and REM (rapid eye movement) sleep stage. NREM stage is again divided into stage 1, 2 and 3.
When we are about to sleep, the EEG records beta waves. When we close our eyes EEG records alpha waves. Then we enter stage 1 which is a transition between wakefulness and sleep. At this stage brain starts to produce theta waves. We at times experience hallucination. For example if we have been playing a game before sleeping for a long time then in stage 1 we might feel we are still playing while we are not.
If a person is in stage 2 then it is harder to wake the person compared to stage 1. More Theta waves along with other types of waves called sleep spindles and K-complexes can be observed using EEG. These help us to be asleep even during loud noises.
In stage 3 delta waves are produced. This stage is also called deep sleep as we have almost no connection with the outer world. It is this stage where we start talking or walking in our sleep.
In REM sleep our eyes start to move very rapidly in different directions (that is why it has been named so), breathing becomes irregular and we are almost paralyzed. Most dreams occur and are registered at this stage. Though we forget most of our dreams but if a person is awaken at this stage, he is more likely to remember what he dreamt. It is interesting to observe that the brain produces beta waves at this time.
During the cycle we follow the sequence of going from N1 to N2 to N3 to N2 to REM to n1and the cycle repeats. The duration of each stage depends on our age, the duration of our sleep etc. Waking up during N3 or REM sleep makes us feel drained and tired. So the best stage to wake up is N1.
Every one of us has a different duration for sleep. Adults usually need around 7 to 9 hours of sleep while children need more. So the best duration of sleep is the one after which we wake up refreshed. So find your own by experimenting with the required duration. Be curious and keep researching.
Barnali Das, IISER, Kolkata
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