Are dreams a representation of inner conflicts, of hidden desires, ambitions and fears? Do they have their own logic? Are they a way that the brain can recalibrate circuits and synapses? Is there a dream world?
Dreams have been a source of fascination for thousands of years and are prominent in literature and religious writings. Many spiritual leaders, such as the great Sioux leader Black Elk had vivid prophetic dreams. Everyone dreams and at times is affected by the emotional content of a dream. They appear to be an important part of human experience. Unfortunately, it is not at all clear what dreams are or how to interpret them.
Dreaming is just one aspect of sleep, and it is one of the supposed three basic different types of consciousness: waking, dreaming, and deep sleep. This post will discuss some general aspects of sleep and mental states as they relate to sleep, and then consider what is known about dreaming and deep sleep.
Dreaming is a Stage of Sleep
Sleep is a complex series of changes in brain states and subjective mental experiences. In the most general terms, there is dreaming and deep slow wave sleep, which are referred to as rapid eye movement (REM) and NREM (non REM) sleep, respectively.
Deep sleep is broken into four stages, I through 4, each having distinct brain waves. We gradually rotate through the stages in cycles of approximately 90 minutes. After the four stages there is a period of REM before another cycle starts. The deepest stage IV is associated with increased learning and memory consolidation. As the night progresses, however, there is less of the stage IV.
Waking consciousness is marked by a vivid continuous sense of reality, both internal and external. It is associated with low cholinergic brain activity and normal activity of amine brain neurotransmitters, the well-known serotonin, norepinephrine, adrenaline, dopamine, and histamine. When awake there are high frequency low amplitude brain waves. Daydreaming has its own EEG signature.
The four deep sleep stages and REM each have their own type of brain waves but they tend to be slow waves. In deep sleep there are muscular movements, including turning over in various ways, but no purposeful movements unless there is a sleep disorder such as sleep walking. In stage one, the lightest slow wave sleep, there are prominent theta waves. Deep sleep is associated with increased learning, and the consolidation of memory. Learning is best if practiced just before sleep. A recent study shows that playing a tune to sleeping musicians during slow wave sleep improves the ability to know that song afterward.
REM sleep, which includes most of the dreaming, has brain waves similar to the lightest deep sleep, stage I. But, very significantly in REM sleep there is a paralysis of the muscles so that no one can physically act out dreams. In REM there is an opposite neurotransmitter profile of low amine neuronal activity, and high cholinergic neuron activity.
In REM sleep there are vivid internally generated scenes, which are bizarre and not logical.
A much smaller amount of dreaming also occurs in stage one deep sleep near the beginning of the night’s sleep, where it occurs in small dream fragments, and also in stage II closer to morning, where it is experienced more as thinking.
Most nightmares come from REM, except for night terrors that come as bursts from deep sleep. It was mentioned above that REM generally has lower levels of amine neuronal activity, which includes norepinephrine. But, in abnormal nightmares (associated with traumatic flashbacks) experienced in Post Traumatic Brain Injury (PTSD) there seems to be higher norepinephrine and a medication that blocks norepinephrine is effective in treatment.
Children have a large amount of sleep, and REM sleep, both of which gradually decrease with age. If we consider the amount of time spent in dreaming, it comes to an average of 2 hours per night, and six years per lifetime, based on sleeping eight hours per night.
Dreaming and REM
Dreams are images, ideas, emotions, and sensations that occur during a time in sleep when the brain is very active, as if awake, but disconnected to the muscles, unless there is a sleep disorder such as sleepwalking. Since there is no current way to measure dreams, the association with REM has arisen through awaking subjects during different parts of sleep and asking them to remember what they were experiencing at that moment.
Dreams can be very short, or long, reaching fifteen minutes or more. The subjective experience of how long it is doesn’t always correlate with the actual length. There can be multiple different scenes in a dream. Since there is less deep sleep, and more REM or lighter sleep as the night progresses, it is thought that dreaming increases later in the sleep.
It is not clear which parts of the brain are used in dreaming. Some important neurotransmitters are muffled during dreams including norepinephrine, serotonin, and histamine. The REM in the first cycle of the night is 10 minutes and the second and third increases to 20 minutes. The later dreams appear more vivid and there is more retention of the storyline. Dreams often include experiences from the last day or week. They often include blended scenes of different locations, and exaggerations of events. Anxiety is the most prominent emotion but all emotions are possible. Negative dreams are more common than positive, and only 8% appear to be sexual, mostly in young people.
Animals also dream. Opossums have more REM and dolphins less REM than humans. Most mammals have been observed dreaming, as well as birds and reptiles.
Sleep, in general, seems to be very important for physiological functioning and many diseases can be triggered by too little sleep. A recent study showed that sleep deprivation causes an immune response equivalent to that of severe stress.
Dreams seem to provide necessary psychological function, but it is not certain what this is.
Lucid Dreaming: a Type of Concentration
A lucid dream is when one feels in control of his actions in the dream and appears to be aware that he is dreaming. Lucid dreaming is recognized as a unique physiological state involving a change in the brain waves to synchronization of mostly 40 Hz in the frontal part of the brain.
It appears that the ability to have lucid dreams can be trained. This training involves practicing concentration on certain tasks while awake, and then attempting to practice them in the lucid dream. An important skill for lucid dreaming is remembering dreams. This is a facility that can increase with effort. It is essential to be prepared to take notes when half asleep upon waking in the morning. Regular practice will greatly increase remembrance of dreams, often from one simple scene to multiple detailed sequences. Another trick noted is to awaken earlier than usual, then go back to sleep. Because there is more REM dreaming late in the sleep cycles, the person often quickly falls back to a light dreaming sleep. This appears to enhance dreaming, and remembering.
One study showed that practicing a task during a lucid dream might increase this ability. The muscular neural circuits are the same during real movement and imagined movement, which is why athletes and performers train by visualizing their skills. A study showed that while watching a ballet performance, a knowledgeable observer uses the same muscle related regions of the brain that the ballet performer is using. This same process seems to work in lucid dreaming where a task is imagined before dreaming and then it occurs in dreaming.
Researchers have asked subjects to move their eyes in a specific way when lucid dreaming to signal that the dreamer can act with volition while in this state. There is a question of whether planning to dream certain dreams can be trained.
During one study of lucid dreams a war occurred and it was noted that those subjects who could lucid dream had less trauma effects. It has been suggested that lucid dreaming enables people to avoid nightmares by waking up earlier, more in command. Some studies have shown increased decision-making capacity in lucid dreamers. Lucid dreamers perform tasks better in waking when they have been practiced while dreaming. The brain regions that are used while visualizing tasks are the same regions used in lucid dreams.
It appears that studying dreams stimulates more lucid dreams. This is analogous to focused concentration while awake allowing increased ability to concentrate. The post on meditation shows a wide range of brain changes associated with these increased abilities from meditation practice.
Confusing Neurobiology of Dreaming
Since we really don’t know why or how we dream, all current explanations are speculative. The general question of the nature of mind and how it relates to dreaming is also speculative.
There is some evidence that the part of the brain that causes REM is not necessarily related to the part that produces the dream. Patients with damage to sensory parietal regions did not dream but those with brain stem damage still had dreams. However, other research does not associate the brain stem with dreaming. A disease called multiple system atrophy causes a state, called dissociates, which includes no traditional sleep but aspects of both sleeping and waking at the same time. Such patients without traditional sleep still have intact memory and learning functions.
It has been shown that individual neurons fall asleep; some think entire columns of neurons in the cortex fall asleep. When enough neurons are asleep a person falls asleep. A previous post on neurons showed that many neuronal activities, such as sleep, are initiated with democratic decision-making. When people are deprived of sleep long enough, enough neurons sleep to cause what is called micronaps, (sleeping for seconds). These micronaps increase until the person falls asleep.
One theory of sleeping is that it functions to transfer short-term memory to long-term memory. But, this is based on little evidence.
Unlike the clear relationship between deep sleep and learning, the relation of dreaming to learning is very confusing. After learning people generally have more REM sleep, and in studies, interrupted REM dreaming states negatively impact learning ability. This has been confounded by a case history of a patient with a disorder who did not sleep or dream for years still was able to learn. Also confounding any simple understanding is that serotonin and norepinephrine related antidepressants (SSRI and SNRI) both decrease the amount of REM sleep, but enhance learning.
The brainstem is definitely involved in sleep and orchestrates connections to the cortex and spinal cord. This center stimulates waking, and sleeping, allows sensory data flow, and modulates sensory flow. But, it is not clear that it is related to dreaming.
Another theory is that sleep loosens neural connections creating more flexible associations, sort of a shuffling of the deck of cards. A study that might give credence to this theory is that synapses seem shift, and lessen during sleep.
It is also possible, as some scientists think, that deep sleep and dreaming may just save energy and allow rest. They may have no other meaning.
States of Consciousness
In both the scientific and spiritual literature, consciousness has been considered to exist in three primary states, that is, waking, dreaming and deep sleep.
There are also other states that are intriguing in their relation to these three basic states. Hypnagogic hallucinations are vivid dreamlike experiences when we are just falling asleep or waking up. Others include hallucinations, visions, flashbacks, near death experiences, and the subjective experiences associated with psychedelic drugs. There are also very unusual mental states associated with savants, including traumatically generated savants. Thus far all of these have been analyzed as part of the three basic states. Future posts will discuss these complex subjects.
The Question of Awareness in the Three Basic States (Waking, Dreaming and Deep Sleep)
It has been clear that awareness exists in waking. But as noted previously, conscious will has to be fostered and exercised or most functioning will be unconscious (see posts on Attention, Suggestion and Free Will). In the waking state the practice of meditation seems to increase the ability to focus and concentrate (see meditation post) and helps efforts to be more conscious.
The state of dreaming was previously considered to not allow awareness and volition. But, with the research in lucid dreaming there appears to be a trained capacity to be aware in dreams. This is analogous to meditation training in the waking state, in that it fosters conscious awareness.
Science however, has not seen any evidence that there is awareness in deep sleep, the third state of consciousness.
In the ancient meditation literature, the deepest states of meditation were compared with deep sleep, except the meditative experience included a deep bodily sleep with mental awareness. The learned ability to be aware during an extremely deep relaxation, that is equivalent to deep sleep, is analogous to learning to be lucid during dreaming, and becoming more conscious during waking.
In favor of this conjecture, there is research on advanced meditation that shows the slow brain waves of deep sleep.
If it were true that, through meditation practice, awareness can exist in a state equivalent to deep sleep, then the multiple benefits of both deep sleep and meditation would be occurring at the same time. The learning, memory consolidation and energy giving properties of deep sleep would be entwined with the multiple beneficial effects of meditation.