On average, we sleep one-third of our lives. Completely defenseless and paralyzed, we drift into the world of dreams. We need sleep, but despite the dynamic development of neuroscience, we still do not know why. Scientists are inclined to the theory that sleep has a primarily regenerative function. Then we use less energy. Sleeping at night has been an evolutionary advantage.
During sleep, the brain is in various states of electrical activity. In the REM phase, we experience dreams. Even if you do not remember them, you can be almost certain that you took part in the nighttime performance. There were probably several such performances and each of them lasted about 1.5 hours. In this phase, the eyeballs move very fast.
DOES A BLIND PERSON DREAM?
It is puzzling how blind people dream. It depends on the time when the blind person has lost sight. If this happens very early or from birth the blind person experiences the activity of the posterior occipital lobe (largely responsible for seeing, visual associations, analysis of shapes, depth, movement, colors) while touching or listening. Blind people experience different ideas about objects. They can describe them, know the shapes of objects, smell, temperature, taste, or texture. They are also dreams, but it is impossible to tell how they differ from the dreams of seeing people. This is one of many puzzles of awareness. It turns out that the later a person loses sight (at the age of 7), the more visual content they experience in dreams.
NEUROPLASTICITY OF THE BRAIN
The visual cortex in blind people is taken over by other senses. In turn, in one of the tests on cats after their birth, their eyelids were sewn on. After some time from the removal of the blindfold, they were not able to see. Their brains did not develop the neuronal circuits responsible for seeing.
The visual cortex in the posterior occipital lobe shows dynamic changes due to the loss of vision. It is then very quickly absorbed by other senses. Hence we are talking about sharpening the senses of sound or touch. The activity of the occipital cortex while touching or listening could be seen as early as 40-60 minutes after artificially cutting off visual stimuli. After such a short time the visual cortex was taken over by other senses. Likewise, better results in learning Braille were achieved by people who had their eyes covered for 5 days than by people who were not introduced to this everyday obstacle.
This is one example of brain neuroplasticity. If the brain can be more efficient, it uses the available areas. It is like a graphic card. Basically it is used to visualize images but you can use it for calculations as a crypto vault digger does.
THE VISUAL CORTEX IN FIGHT
In their latest, but not yet peer-reviewed research, Don Vaughn and David Eagleman (you may associate him as a well-known promoter of brain knowledge) present the theory of defensive activation. They assume that dreams defend the visual cortex from being seized by other senses. They noted a correlation between brain neuroplasticity in 25 primates depending on age and sleep time in the REM phase when they experience dreams.
As we grow older we need less sleep because the brain is less plastic. For example, an infant, as it sleeps for up to 16 hours in the first 15 days of its life, experiences sleep dreams for half that time. In turn, at the age of 70, dreaming for less than 8 hours, dreams do not appear for even 2 hours. The decrease in plasticity with age makes it more difficult to recover from damage like a stroke at a later age.
Sleep in the REM state would therefore protect the visual system from being taken over by other senses. This is supposed to happen because the visual cortex remains active and significantly simplifying – it shows not reality, but dreams.
If the brain does not receive information about the objects, it will somehow earn such information on its own. This is especially visible during the so-called sensory deprivation. Reports of visual or auditory hallucinations appear in the accounts of Alcatraz prisoners punished by a stay in a dark isolation room. A similar effect can be achieved in the deprivation chambers, known as floating chambers (such a marketing name is more encouraging to use). The client immersed in the salt solution rises and remains cut off from most senses. Interestingly, there may be experiences of itching, scratching, even though there is actually nothing like that. This is an example of hallucinations, but not visual. It seems that in states of sensory deprivation in the absence of stimuli, the brain itself creates visual, auditory, or visual impressions.
It is very possible that it is the same defense mechanism that the brain uses during REM sleep to protect a particular area of the brain from being taken over by another sense.
WE KEEP AN EYE ON RESEARCH
Although the research has not yet been reviewed by the scientific community, the concept presented is very convincing. We will follow the comments and certainly mention David Eagleman.
Remember that this article does not encourage experiments with temporary blindness. You must remember that the experiments are carried out under controlled conditions. By doing so, you are putting yourself in danger, especially if you do it without the support of another person who cares about your safety. Instead of experimenting in this way, go to The Invisible Exhibition.
David M. Eagleman, Don A. Vaughn, The Defensive Activation theory: dreaming as a mechanism to prevent takeover of the visual cortex, https://doi.org/10.1101/2020.07.24.219089