Scientists had propounded many theories and hypotheses about the cause and effect of sleep and dreams: Most of the theories were schematic and one-sided. But some of the theories contained interesting arguments which are even today considered as valid. They include vascular theory, chemical theory and sub-cortical theory.
According to the vascular theory, sleep is evoked by gradual decrease in the inflow of blood to the brain. Here too there were different opinions: A section of the proponents of the vascular theory stressed that it was not decrease in blood circulation in the brain but increase of blood flow into the brain that induces sleep. Both these theories were found baseless because natural sleep is different from sleep-like states of stupor, coma or shock that takes place either due to lack of blood circulation or excess inflow of blood into the brain.
Chemical theory says that various toxic products of metabolism accumulated in the body during waking hours cause sleep. The chemical theory of sleep was found unsubstantiated in the context of the very nature of natural sleep. Accumulation of chemical substances in the body during wakeful hours is a slow process and in that case sleep ought to have to set in slowly, but the fact is otherwise: Both sleep and waking up take place almost suddenly. Had toxicity been the reason for sleep, both the said processes were to be slow extending for hours. Another contradiction of chemical theory is the well-known fact that it is enough for some persons to sleep for only a few minutes to get back refreshed and active. That apart, tests conducted on conjoined twins who had separate nervous systems and common blood circulation, totally disproved the chemical theory. In those tests, when one of the twins was asleep, the other one was found awake and playing with its toys: If chemicals in the blood caused sleep, both the twins ought to have fallen asleep at the same time and on the same spot. That did not happen in repeated experiments on the twins.
Sub-cortical theory says that there is a specific centre in the central nervous system in the sub cortical area which controls sleep. The proponents of this theory argue that since sleep is a vital activity of the physic, there must be a special centre for sleep in the brain as in the case of all other important bodily functions like digestion and respiration. Sub cortical area of the brain contains special nerve formations through which stimuli from environs reach cerebral cortex and excitation of sensory centres takes place. The excitation leads to inhibition: To that extent sub cortical area helps induction of sleep. But it is only a contributory factor of sleep and the claim of scientists that there is a sleep centre in the cortex is baseless.
The Vascular theory, Chemical theory and Sub Cortical theory are unscientific and biased. A theory can be called scientific when it is not limited to a simple description and when it is not limited to a listing of favourable and unfavourable factors. Theory stands scientific only when it divulges the nature of the phenomena.
Living organism including humans is always engaged in some activities or the other during wakeful hours. The organism may be sitting idle or may be engaged in doing something or the other. Whatever be the case, the central nervous system of the living body would be constantly reacting to various stimuli from both the internal and external environments. These reactions would include seeing, hearing, smelling, tasting and motor activities. As a result of the continuous reaction, the nerve cells in the central nervous system would start losing its vital energy over a period of time: Then the nervous system would stop responding to the stimuli to save the nerve cells from wear, tear and possible destruction. This is an automatic reaction of the brain produced by inborn reflex actions. The reflex action creates a state of inactivity or inhibition across the nervous system. The inhibition would gradually spread to the body as a whole. The state of inactivity or inhibition provides rest to the cells and the energy lost during wakeful hours would thus be recouped. The state of restful inactivity called inhibition is what we call Natural Sleep.
Even during the inhibitory state of sleep, there arise situations that work as stimuli from environs. These stimuli frequently disturb the ongoing state of natural sleep. The situations that provide stimuli for disturbance may be body pains, heat, cold, insects, uncomfortable sleeping places and various types of mental agonies. They would reach out to the nervous system through different sensory centres. This may cause sudden waking up from sleep. Such an abrupt waking up is injurious to nervous system and it is non-conducive for recuperation of the lost energy in the nerve cells. A nervous action in the form of unconditioned reflex action would in such situations bring in certain dramatization of things, matters, events and experiences in the form of Dreams. That is the background of dreams which take place during disturbed sleep in the day to day life of living organisms.
Dreams prevent sudden waking up from sleep, even if it is for a few seconds or a fraction of a second. That short period of time will be enough for the body to prepare itself for waking up without causing harm to the central nervous system.
Dreams have no specific themes, story lines and agenda. The claim of believers that dreams reflect what is going to happen in future have no proof of evidence. Similarly the claims that dreams are indicative of the thoughts and actions of the dreamer are also baseless.
Sleep and Dreams are closely related. It is dreams that help sleep to continue its duty without sudden interruption that might badly affect good health. Dreams can rightly be called as “Close Friend and Supporter” of Sleep.
Dreams, whether good or bad, are essential part of maintaining good nervous system and healthy living. Uninterrupted sleep without frequent waking ups is the essential physiological requirement of every living organism. Dreams act as coordinator of this vital requirement of Sleep.