Consciousness

There are several circadian rhythms.  Variations in your heart rate, blood sugar, and body temperature correlate with what time of day it is.  In AP Psychology, the circadian rhythm we care about the most is the sleep wake cycle.

You may have noticed that you tend to feel sleepy and wake up around the same time of day.  You may find that during some parts you are more alert, and during other parts of the day you are sleepier.  Your brain helps coordinate a series biological changes as the day progresses.

This creates a predictable pattern of sleepiness and wakefulness.  Yet, sleep disruptions and sleep disorders are common.  Both of these issues can disrupt the normal 24 cycle that governs sleep.

This also makes up one of the most profound changes in consciousness that we experience on a daily basis.  When we are awake, we are aware of external events and our own conscious thoughts.  We are also aware of how our own internal states change over the day.  For example, you may feel hunger or thirst.  When we are asleep, we are not aware of external events or our internal states.

There are exceptions. Some people do have conscious thoughts while dreaming. This is a lucid dream. Lucid dreams are common, but they not everyone has them. Also, the transition between states can create states of awareness that are unique. Hypnogogic hallucinations are odd perceptions that occur during these transitional states. We'll talk about them in more detail later, but they are unique experiences that occur during this transition.  ​

Your body goes through four predictable stages of sleep each night.  These stages of sleep are NOT a circadian rhythm.  They do follow a pattern, but that pattern doesn't repeat itself over a 24 hour period.  Instead, it repeats over a period of about two hours.  This means the average person will have several sleep cycles each night.

Each of these stages has distinct characteristics.  There are specific observable behaviors and subjective experiences that occur in these stages.  Furthermore, the brain releases specific brain waves during each stage.  The invention of the EEG allowed scientists to measure these brain waves. Scientists classify the sleep stages into two groups based on data from the EEG. The two categories are Rapid Eye Movement (REM) sleep and Non-Rapid Eye Movement Sleep (NREM).

There is much we do not know about sleep.  Sleep is difficult to study because many technologies are loud or invasive. This prevents people from falling asleep. Even if people do sleep, they may wake up or have worse sleep than the usually do. Human limitations also make studying sleep challenging. We are not conscious during sleep and forget our experiences wile sleeping. This eliminates survey and structured interviews for many topics related to sleep.

A quick note on the curriculum changes: AP Psychology used to cover all the sleep stages. Students also had to know each stage's distinct traits and brain wave patterns.  They also had to know the order these stages occurred in.  No more!  This section is simpler now, so we won't get into all the details here.  ​

Non-Rapid Eye Movement sleep (NREM) has three distinct stages. A person enters NREM sleep when they first fall asleep.

The first stage of sleep reveals some interesting things about human consciousness.  This stage occurs when we transition from being wakefulness to sleep.  As we discussed earlier, our consciousness shifts.  Hypnogogic sensations are one example of this.  One of the most common forms of this phenomenon are hypnogogic hallucinations.  This occurs when falling asleep alters our consciousness. People perceive something that is not happening.  Hypnogogic hallucinations include hearing your name or seeing geometric images in the dark. It is also common to feel like you are falling or floating.  While these experiences can be disturbing, they are also very common.  Well over half of the population experiences some form of hypnogogic hallucination.

People in the first stage of NREM sleep tend to be relatively easy to wake up.  As a person transitions into the deeper stages, their sleep gets deeper and it is more difficult to wake them up.  People also become less aware of internal and external changes.  We very rarely remember anything that happens during this time.

There are many interesting aspects of the second and third stages of NREM sleep. They are not emphasized in the new AP Psychology curriculum.  That means its time to move on to the next big shift in consciousness - REM sleep.  ​

Scientists named REM sleep after one of it's most obvious characteristics.  When a person is in REM sleep, their eyes dart around as if they are looking at something. As it turns out, we regain some consciousness during REM sleep. This is because most dreams occur during this stage.

Dreaming represents a profound shift in consciousness.  Unlike REM sleep, humans can be aware of and remember their dreams.  We may even be aware that we are dreaming. Lucid occur when the dreamer knows they are dreaming. Some people who experience lucid dreams are able to control the outcome of the dream. This could include experiences that are impossible in the real world.

At the same time, awareness during sleep has limitations. It only extends to things we have imagined to exist. Humans in REM sleep are not aware of external events or changes.  This awareness is also fleeting.  Dreams have own logic that does not make sense once we are awake. Dreams are often forgotten soon after waking up.

During REM sleep our brains emit waves that are like the ones created during wakefulness.  Unlike wakefulness, the muscles of your body don't move during this stage.  People who wake up during REM sleep may find that they cannot move.  REM sleep is sometimes called "paradoxical sleep." A paradox is something that contradicts itself. In this case, it refers to the idea that our brains look like we are awake, but our bodies are inactive.

REM sleep increases over the course of the night.  In contrast, NREM sleep decreases. REM rebound occurs when a person does not get enough REM sleep for a period of time. Their body will compensate by spending more time in REM sleep when they do sleep.  This suggests that REM sleep and/or dreaming serves an important function.  Unfortunately, there is not a clear scientific consensus on what this function is. We'll explore this debate in a future post.