The Mechanics of Dreaming
Written by: Michelle Belanger
Many people have no recollection of dreaming, and yet we know that everyone enters REM sleep on average four times a night. Even blind people experience REM sleep, unless the muscles of their eyes have completely atrophied. We can tell that dreaming serves a crucial physiological function only by negation: deprived of REM sleep, people have trouble thinking clearly and will begin to experience visual and sometimes auditory hallucinations.
Thanks to developments such as the EEG or electroencephalogram, modern scientists can measure the changes in brain wave patterns experienced during sleep and dreams. From this, we can identify four distinct stages of sleep. We also know that dreams occur in what is called “emergent stage one sleep,” which happens as we start to come back up from the deeper brain wave patterns known as delta waves. On the edge between sleeping and waking, our brain waves move in patterns called alpha and theta waves. The theta waves are high amplitude, low frequency waves, which means that they are slow, but have very high peaks. Those peaks begin to increase in patterns known as sleep spindles and the alpha waves drop off, until only theta waves remain. Both of these stages only last a few minutes each. Stage two, the theta waves accented with sleep spindles, gives was to deep sleep, otherwise known as delta sleep. Deep sleep is indicated by delta waves, which are very slow waves compared to alpha and theta waves. We go through two stages of deep sleep, one with mixed delta and theta waves, the other with more than fifty percent delta waves.
Dreaming does not occur directly from deep sleep. Instead, the stages quickly reverse themselves, and we emerge into REM sleep. Our first stage of REM sleep lasts approximately ten minutes. When we dream, brain activity jumps, moving in high frequency beta waves, intermixed with the occasional theta wave. Beta waves are not exclusive to sleep; our brains produce beta wave activity when we are awake as well. A full series of these stages takes about ninety minutes to complete. The average person experiences four such series in a night, with the periods of deep sleep gradually waning and the periods of REM sleep increasing to as many as thirty minutes in length. The final period of REM sleep is not only the longest, it is also the one that lingers most clearly in memory as we emerge from sleep.
And yet, as detailed as this map of brain wave patterns can seem, this is like peering into a room through thick glass block and trying to describe the interior. All EEGs provide are tantalizing bits of information that still give us no definitive look at what a person is actually experiencing in the state of dreams. For all our technological gadgets, the realm of dreams remains the solitary province of the sleeper.