Activation-synthesis hypothesis

The activation-synthesis hypothesis, proposed by Harvard University psychiatrists John Allan Hobson and Robert McCarley, is a neurobiological theory of dreams first published in the American Journal of Psychiatry in December 1977. The differences in neuronal activity of the brainstem during waking and REM sleep were observed, and the hypothesis proposes that dreams result from brain activation during REM sleep. Since then, the hypothesis has undergone an evolution as technology and experimental equipment has become more precise. Currently, a three-dimensional model called AIM Model, described below, is used to determine the different states of the brain over the course of the day and night. The AIM Model introduces a new hypothesis that primary consciousness is an important building block on which secondary consciousness is constructed.

With the advancement of brain imaging technology, the sleep-waking cycle can be studied as never before. The brain can be objectively quantified and identified as being in either one of three states: awake, REM sleep, and NREM sleep due to these advanced methods of measurement. It has been shown that global deactivation of the brain from waking state to NREM sleep occurs, and a subsequent reactivation during REM sleep, to a degree greater than during waking.Consciousness and its substates, primary consciousness and secondary consciousness, play a part in identifying the state of the brain. Primary consciousness is the simple awareness of perception and emotion; that is, the awareness of the world via advanced visual and motor coordination information your brain receives. Secondary consciousness is an advanced state that includes both primary consciousness and abstract analysis, or thinking, and metacognitive components, or the awareness of being aware. Most animals show some stages of primary consciousness, but only humans have been experimentally shown to experience secondary consciousness. The cycle of waking-NREM-REM sleep is essential to mental health of mammals. It has been shown through experimentation that animals subjected to inability to enter REM sleep show an immediate attempt to quickly enter REM stages and long-term effects on motor coordination and habitual motor habits, eventually leading to the death of the animal. It has also been shown that homeothermic animals might require sleep to maintain body weight and temperature.

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