Understanding dreams -the comprehensive, interdisciplinary way: A review

Dreams are virtual repetitions during sleep of what we perceive and act on while awake. Sensory inputs and motor outputs are suspended during dreams, and the ascending reticular activating system is deactivated. The brain's electrical networks differ between waking and sleeping states, yet people still see images of persons and places in dreams. Dreams may be unconscious recollection and replay of past experiences, linked to memory formation, consolidation, and retrieval. The same brain parts involved in memory and emotions—hippocampus and amygdala—are involved in dreams, with higher brain centers constructing a storyline. The posterior cortical hot zone is considered the factory of dreams. Multiple theories and approaches exist, none holding the whole truth, and this article reviews neuroanatomy, electrophysiology, REM sleep changes, and related clinical entities.

Study at a glance

Abstract

Dreams are virtual repetitions during sleep, of what we perceive and act, in reality, when we are awake. The basis of wakeful state, is due to the sensory inputs from the sensory organs (through the ascending tracts) and the motor output from the respective brain centres (through the descending tracks), as well as, due to the activated ascending reticular activating system. (ARAS) and the posterior hypothalamus. In the dream state, both these sensory inputs and motor outputs are suspended and the ARAS is deactivated. Even the brain's electrical networks ie the Salience and the Default network,(DMN) are different, during working and sleeping States, respectively. Yet one can see the images of persons and places etc, in the dreams. It follows, that the dreams could be, the unconscious recollection and replay of the past experiences during the sleep. Thus, the dreams are linked to the memory formation, consolidation and it's retrieval. Truly, the parts of the brain involved in dreams, are the same as those involved in the consolidation, storage and retrieval of the memory, (Hippocampus) and emotions (Amygdala) and the attempted meaningful interpretation, in the form of a storyline, by the higher brain centers, in the neocortex (like medial prefrontal cortex, etc). In fact, the hippocampus has been shown to utilize the memory, to construct novel, imagined scenarios and simulate possible future events. An area, just above the nape of neck called the “posterior cortical hot zone", is considered to be the “factory of dreams “.The electrical waves (like the Hippocampal theta waves and pontine -geniculate -occipital waves) and the neurotransmitters, (like cholinergic, glutamatergic, adrenergic, serotonergic and GABAergic ) link the respective centres involved in the dream process. Several theories (like Freud's, Carl Jung',s, activation- synthesis theory etc),are put forward, as well as, several approaches (like Psychodynamic, behavioral and Neuroscience approaches) are followed.The multiplicity of, the theories and approaches, is a testimony to the fact that none of them, has the whole truth. A comprehensive interdisciplinary approach is attempted in this article, by reviewing the various facets of the dreams, like the neuroanatomy of the structures involved, their interconnections, the electro -physiology of the brain, the physiological changes that occur during REM sleep (during which the dreams occur), the clinical entities that mimic the dream- state but are distinct, like, Imagination, Imagery, Recall and the Hallucinations, including, the sleep hallucinations (hypnagogic and Hypnopompic), forebrain Analysis and the forebrain synthesis ete, and sleep disorders (like sleep paralysis, sleep myoclonus) etc., in search of clues, for the better understanding of the subject of dreams.