Overview

Sleep is a state in which the conciousness of the mind is altered. Although sleeping is seen as a time when the body rests and turns off, the brain is very active during the sleep and both thinking and memory continue as normal during sleep, as does awareness and sensitivity to external stimuli such as sound and light. Sleep is essental to human survival and is needed to rest and repair the body and process thoughts.

Sleep Patterns

The use of electroencephalography to detect brain-waves since the mid-twentieth century has allowed researchers to indentify two different states which a brain will alternate between every 90 minutes.

The two states are:

• Non-Rapid Eye Movement (NREM): A relaxed state measured as between Stage 1 and Stage 4 depth. The body is very relaxed and at Stage 4 the body is almost inactive. This state takes up 30% of the time one sleeps and no dreaming occurs while in this state. This sleep is thought to be a time to repair the brain.
  
  
• Rapid Eye Movement (REM): A state where the body is rested but mental activity is as it would be when awake. Characteristics of REM inlude:
  
  • Rapid eye movement under the eyelids (hence the name).
    
  • Temperature and blood flow increasing.
    
  • Dreaming, which is believed to be when the mind processes thoughs and possibly stores information as long term memory.