LearnHub

Feel the hot summer sun on your face. Feel your muscles relax when you breathe in and out. This is all part of consciousness. Consciousness is the awareness we have of ourselves and our environment. Different states of consciousness are associated with different brain wave patterns. Brain waves indicate electrical activity in the brain, measured using an electroencephalograph (EEG). The EEG monitors electrical activity by placing electrodes on the scalp.

There are four main types of brain waves: alpha, beta, theta, and delta.

WHY do we sleep?

• People conserve energy by sleeping periodically.
• Sleep has a protective function because it keeps people tucked away at night, safe from predators.
• Sleep restores body tissues that are depleted during daily activities.

Sleep Research Sleep research has provided a lot of information about what happens to the brain and body during sleep. Researchers study sleep by monitoring subjects who spend the night in labs, and they use various instruments for different purposes: Electroencephalographs (EEGs): record brain waves Electromyographs (EMGs): record muscle activity Electrooculographs (EOGs): record eye movements Electrocardiographs (EKGs): record the activity of the heart.

Stages of Sleep

There are five distinct stages: 1, 2, 3, 4, and REM.
When you’re about to sleep, you will show mostly alpha waves.

• Stage 1: Falling sleep. This lasts a few minutes (beta waves). Heart rate, breathing rate, and body temperature drop, and muscles relax. Fantasies or bizarre images may float around in the mind.
  
• Stage 2: 20 minutes long, characterized by short bursts of brain waves called sleep spindles.
  
• Stages 3 and 4: slow-wave sleep, last 30 minutes altogether (delta waves). Characterized by slow breathing and pulse rates, limp muscles, and difficulty in waking up.

  
  

  At the end of stage 4, people go back through the stages in reverse. When they reach stage 1 again, instead of waking up they go into REM – Rapid Eye Movement.
  

  Here’s an example of a typical single cycle:

  1

  2

  3

  4

  3

  2

  REM

  
  

  REM is a stage of deep sleep, but the brain wave activity resembles that of an alert person. REM is also known as paradoxical sleep because of this. Pulse rate and breathing become irregular, eyes move rapidly under closed lids, and muscles remain very relaxed. Dreams are most vivid and frequent during REM sleep. People typically go through about four sleep cycles during one night. The REM stage of sleep gets longer as the night passes, while stage 3 and 4 sleep gets shorter and shorter. During a night’s first cycle, the REM stage lasts about 10 minutes. The night’s last cycle of REM may be about 40 to 60 minutes. Non-REM sleep becomes more shallow as the night goes on, and eventually the sleeper awakens.

  
  

  Sleepwalking
  

  Most people in stage 4 sleep quiet and difficult to awaken. But sleepwalkers become physically active during Stage 4. They will get up, walk around, have conversations, take baths, get into their car and do all sorts of things. But because they’re still in a deep sleep, they usually don’t remember any of their actions when they wake up.

  
  

  Sleep and Aging
  

  Sleeping patterns change as you get older. Newborn babies spend about two-thirds of their day in sleep. In babies, half of all sleep is REM sleep. When you get older, you tend to sleep less.

  
  Pittaya, Prakhar, Tambako