Consciousness, Sleep, and Altered States

Dreams

Psychoanalytic therapists use dream interpretation in therapy. Modern scientific exploration of dreams suggests they play a role in storing memories and developing neural pathways.
Dream consciousness differs from waking consciousness. Dreams evoke more intense emotions and sensations. They are characterized by illogical thought processes that allow uncritical acceptance of dream events. Experiences that would be impossible in everyday life, such as flying through the air, feel real while dreaming. Dreams are often difficult to remember.

Lucid dreaming is a phenomenon in which dreamers are aware they are dreaming, and may be able to exert some control over dreams. During lucid dreaming, higher levels of activity are detected in the frontal and frontolateral (executive) regions of the brain than during nonlucid REM sleep. Lucid dreamers typically report greater awareness about the unreality of dream objects and characters and greater awareness of their sleeping physical body.

Austrian neurologist Sigmund Freud proposed that dreams are the result of unconscious processes expressing hidden desires, fears, and wishes a person finds threatening or unacceptable while awake. Freud distinguished between a dream's manifest content (its apparent topic or superficial meaning) and latent content (its true underlying meaning). For example, a common dream among college students involves discovering they are naked while giving a presentation in a classroom full of people. The manifest content is being naked in front of a room full of people. The latent content might be fear of exposure, namely fear that people will realize the dreamer is inadequate or a fraud. The problem with Freud's theory is that it is not systematically testable and therefore lacks scientific support. Any dream can be interpreted in several ways, and it is impossible to determine which interpretation is correct.

Another dream theory is the activation-synthesis model, which proposes dreams are produced when the brain attempts to make sense of random neural activity. During waking consciousness, the brain receives input from the external world. It uses that information along with stored knowledge to assign meaning to experiences. During dream consciousness, the brain receives information from internal neural activity. That internal neural activity may be totally unrelated to external reality, yet the brain still tries to assign meaning. The side effect of this neural processing is a jumble of dream events that are not logically related.

Activation-Synthesis Theory of Dreams

According to the activation-synthesis model of dreaming, dreams arise when the logic-oriented cerebral cortex attempts to make sense of random activity in the pons, which sorts and relays messages to other brain regions.
Modern scientific exploration of dreams suggests they play a role in developing neural pathways (links in the brain) and storing memories. Research in rats shows a lack of REM sleep reduces the growth of new brain cells in the hippocampus, which can affect memory. Allowing the rats to sleep normally again does not reverse the lack of brain cell growth. In humans, REM sleep deprivation negatively affects the formation of procedural memories, which are related to knowing how to do tasks (such as riding a bike or playing a sport).