Pretty much every single night, we all go through an incredible change: we go from being fully conscious and spend hours each night in a semi-conscious states, drifting through a strange dream state, moving through cycles of brain activity. As we wake in the morning, we barely remember the hours we have spent asleep, except for those rare moments when the dream is so vivid we cannot forget it. We all sleep, but most of us do not really know what happens when we sleep.
Physiologically, when we sleep, our temperature and blood pressure drop, our body elongates as the muscles relax and functions such as brain activity, breathing and heart rate will change dramatically as we go through the different sleep cycles.
Brain activity is one of the keys to understanding what happens when we sleep. For years, scientists believed that sleep was a period of zero brain activity but in the last half century, research has shown that our brain activity changes drastically when we go to sleep and during sleep.
Sleep is divided into two particular types, rapid eye movement (REM) and non-REM. These are characterised by different levels of brain activity. REM is a period of high brain activity and is the time of vivid dreaming, while non-REM is a period of lower brain activity.