The Mind at Night

Considering that we spend a third of our life asleep, it makes sense to know about what’s going on when we’re sleeping.

It all starts with a period of pre-sleep, when our mind settles down, stops trying to make decisions and plans, and enters an almost meditative state to prepare the mind for sleep.

From there, we enter light sleep, which covers the first two stages.

During the first stage, or sleep onset as it’s known, we often see flashes of disjointed images, known as hypnagogic imagery. This is the brain’s way of sorting through the day’s experiences and deciding what to trash and what to stash. Some things get forgotten, while others are deemed important enough to store in our long-term memory.

Then stage two begins and our brain winds down further to make way for the stages of deep sleep that follow.

These deep third and fourth sleep stages are characterized by slow brain waves, and we generally cycle through the first stages once again before arriving at the fifth and final stage, which is marked by REM – or rapid eye movement – sleep.

It takes between fifty and seventy minutes to get through the first four sleep stages, and the REM period can be as short as ten minutes. So, altogether, the process lasts about ninety minutes, with the combined stages of deep sleep and REM usually accounting for a quarter of our total sleep during any given night.

While all five stages have their own important functions, it’s at the fifth REM stage when we experience our most vivid dreams and when our mind goes through its internal processes.

In the blinks that follow, we’ll take a closer look at how important these dreams have been and continue to be.