Achromatopsia seeing a gray reality, without being pessimistic

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Simon Doyle
Achromatopsia seeing a gray reality, without being pessimistic

The perception of color a merely subjective and personal experience.

"Reality cannot be seen if it is not from the point that each one occupies, fatally in the universe." J. Ortega y Gasset

Through perception we collect information from the outside through our senses and interpret it in unique ways. Therefore, even if two people are in the same space and have experiences that seem to be "the same" or similar, each one will have a different conception about what happened, since many factors that change from person to person influence this cognitive process.

Contents

  • All sensory experience is subjective
  • How is the vision given?
  • What is achromatopsia?
  • Genetics and achromatopsia
  • Brain achromatopsia
    • Other visual disorders of brain origin with respect to color are:
  • Diagnosis and treatment
    • Common treatment for Achromatopsia
    • What we see is not what it seems
  • Colors and emotions
    • Links
    • Bibliographic references

All sensory experience is subjective

The perception of color is a subjective experience lived in each person in a unique way, it could be said that color is a quality. Well the eye sees and the brain interprets what is seen.

Experiences are subjective and science defines them as a residual collateral effect, that is, they are reducible to the information processing and anatomical structure of each organism. Sight is a very valuable sense, because through this sense we can perceive and access the information found in our environment. For this reason, Aristotle affirmed that: “we arrive at knowledge through the senses”. Vision involves the almost simultaneous interaction of the two eyes and the brain through a network of neurons, receptors, and other specialized cells..

How is the vision given?

The sense of sight is given through the path of light through the interior of our eyes. Since without light, eye vision is not possible. In the first stage, light enters the eye through a series of transparent tissues, such as: the cornea, the aqueous humor and the vitreous humor. The retina contains two types of light receptor cells, called rods and cones. The image reaches the retina and that is where the sensory cells are activated, which are the ones that transform light into nerve impulses, this phenomenon is known as phototransduction, since these cells transmit visual signals from the eye to the brain through of this process. The poles provide vision in low light conditions (night vision). And the cones provide vision in bright light (day vision), including color vision.

Thus, the nerve impulses created in the retina begin their way to the brain, specifically in the cerebral cortex, through the optic nerve. Subsequently, the brain is responsible for recognizing, processing and interpreting these impulses, turning them into images that make sense to us. Visual perception is then a sensory process that begins in the retina, continues in the thalamus and ends in the cerebral cortex, where the stimuli that surround us become conscious. The human brain also makes a subjective elaboration of the world that surrounds us, making it unique in each individual.

At the level of the ganglion cells of the retina, the three-color code changes to a color opposition system. These neurons respond specifically to primary color pairs, with red opposing green and blue opposing yellow. Thus, the retina has two types of color-sensitive ganglion cells: red-green and yellow-blue..

Other ganglion cells that receive color input do not respond differentially to different wavelengths, limiting themselves to encoding relative luminosities in the center and periphery. These cells serve as detectors for black and white. Likewise, they encode information on the relative amount of light that enters the center and periphery of their receptor fields and, frequently, on the wavelength of that light. The striate cortex and visual association cortex perform further processing of this new visual information that is received from the magnocellular, parvocellular, and coniocellular layers of the dorsal lateral geniculate nucleus. Therefore, the role of the striated cortex in the analysis of color is fundamental in this process..

The magnocellular system is color blind and sensitive to movement, depth, and small differences in brightness. On the other hand, but getting involved in the same process, we find the parvocellular system, which transmits to the primary visual cortex the information necessary for the perception of color and small details, receives information only from the red and green cones. Neurons in the striate cortex send axons to the extrastriate cortex (region of the visual cortex that surrounds the striate cortex).

Laboratory animal studies indicate that neurons in a specific subarea of ​​the extrastriate cortex: V4, are involved in both shape and color analysis. The lesions of area V4 suppress the constancy of color referred to the precise perception of color under different lighting conditions, (Zeki, 1980).

What is achromatopsia?

It is a non-progressive condition, characterized by a partial or total absence of color vision. People with complete achromatopsia cannot perceive colors other than black, white, and gray scales. Incomplete achromatopsia is a milder form of the condition, which allows some degree of color discrimination, also known as color blindness. These vision problems develop in the first months of life, when it is not as a result of another triggering event.

It also involves other vision problems, such as: increased sensitivity to light and glare, known as photophobia; involuntary eye movements (nystagmus); in some the visual acuity is significantly reduced. Subjects with achromatopsia may also have farsightedness and, less commonly, myopia..

Genetics and achromatopsia

It affects approximately 1 in 30,000 people worldwide. complete achromatopsia occurs frequently in the population of the inhabitants of Micronesia, since between 4 and 10% of the people of this population have a total absence of color vision, in this population mutations have been found in the gene CNGB3. Mutations in the genes NGA3, CNGA3, CNGB3, GNAT2, PDE6C and PDE6H are found in the world population.

It is an autosomal recessive disorder, which means that for the disease to develop, both copies of the gene must be mutated. Thus, the person who has only one carrier gene will not develop the disease, because the other copy is working well. For a person to develop it, both parents must be carriers. This gives a family with an affected child a 25% (1 in 4) risk for each pregnancy. There would also be a 50% chance that the child is a carrier.

In people with complete achromatopsia, the cones are not functional. The loss of function of the cones leads to a total lack of color vision and in turn generates other vision disorders. People with incomplete achromatopsia have limited color vision, as well as other vision problems.

In some people with this condition, mutations in the genes that commonly affect the other population with achromatopsia have not been identified. In these individuals, the cause of the disease is unknown. Other genetic factors that have not been identified and likely contribute to this condition.

Proportion of pathogenesis detected by this method

GENPROPORTION OF ACROMATOPSY ATTRIBUTED TO PATHOGENIC VARIANTS IN THIS GENESEQUENCE ANALYSISANALYSIS OF THE ELIMINATION / DUPLICATION OF GENES
CNGA35% -23% in Europeans

28% in Israelis and Palestinians

80% in Chinese

~ 100%No reports
GNAT2Families~ 100%Family
PDE6CFamilies~ 100%No reports
ATF6Families~ 100%No reports
PDE6HFamilies~ 100%No reports
A strangerFamiliesDoes not applyNo reports

Achromatopsia is inherited in an autosomal recessive manner. At conception, each sibling of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not being a carrier. “Carrier” testing for at-risk relatives and prenatal testing for higher-risk pregnancies are possible if pathogenic variants have been identified in the family.

Brain achromatopsia

Achromatopsia is one of the specific visual disorders of brain origin, which involves the specific loss of the ability to see the world in color. Those who suffer from it tend to perceive a monotonous world, mainly in terms of color, since colors, as mentioned, can produce emotions and modify our perception at times, some patients describe their vision as "dirty shades in gray scale", their vision is similar to an old black and white film. It is important to mention that when one sense is partially or totally reduced, others tend to develop, it is the wonder of the brain, which always seeks and finds ways for us to be functional and adaptable to our environment!!

From the point of view of functional specialization, the degree of specificity is assessed. Patients with achromatopsia can write, read, differentiate shapes and depths generated from movement. In fact, some can see better when there is not as much light, which gives them excellent night vision skills or when there is little light, such as fishing for certain species, which is best done at night, as they "see better in the shadows." . Thus demonstrating that although they are "limited" in this sense, they can take advantage of their different capacities in other areas, with an exercise of self-knowledge, acceptance and will.

On the other hand, functional magnetic resonance imaging studies in humans (fRMN) show that there is a color-sensitive region in the inferior temporal cortex: V8. Lesions that cause achromatopsia or colorless vision damage the V8 area or other brain regions that provide V8 input. In addition to losing color vision, people affected by this injury cannot even imagine colors or remember those of the objects they saw before the brain damage occurred..

Other visual disorders of brain origin with respect to color are:

  1. Color anomie: colors cannot be named although they can be recognized.
  2. Color agnosia: colors cannot be recognized.
  3. Hemiachromatopsia: it is a state in which only half of the visual field is perceived as colorless, while the other half is assimilated with colors in a normal way
  4. Transient achromatopsia: A unique case study revealed the case of a 54-year-old man who suffered from repeated seizures which were accompanied by a sudden and transient loss of the ability to see the world in color.
  5. Achromatopsia of carbon monoxide poisoning: it is a phenomenon in which color vision is preserved or is much less affected than other attributes of vision and is caused by injury to the ventral pathway.

Diagnosis and treatment

It is established through medical and family history, examinations for nystagmus, visual acuity tests, evaluation of color vision, and fundus examination. If achromatopsia is suspected, additional tests may include an optical coherence tomography, fundus autofluorescence, visual fields, electroretinogram (ERG), optical coherence tomography (OCT), and psychophysical tests among others..

Carrier testing for at-risk relatives and prenatal diagnosis for higher-risk pregnancies are possible if pathogenic variants have been identified in the family.

Common treatment for Achromatopsia

Very specialized dark filter lenses are used as red-scale contact lenses to reduce photophobia, to enhance and improve visual acuity; special graduation for low vision; it is advisable to have an ophthalmological examination every 6 to 12 months in children who suffer from it and every two or three years for adults.

As part of the inclusive culture, it is advisable to always give these people preferential class seats to those who have this condition and support them in what we can when they require it and it is within our possibilities..

What we see is not what it seems

"In this world nothing is true, and nothing is a lie, it all depends on the glass you look at." Popular saying

The things and colors that we perceive are not exactly as they are shown to the senses, some features that we perceive in them belong to them as real characteristics and others do not, since they go through the process of sensation and perception..

Speaking in this sense, objects have two kinds of qualities. The primaries, which are inseparable from a body, regardless of its state, which produce simple ideas, such as solidity, extension, figure, movement or rest and size, that is, that knowledge can be expressed in terms mathematicians. On the other hand, secondary qualities are those that do not exist in things themselves, and, in a certain sense, are subjective, such as heat, color, sounds and taste, since these sensations depend on the subject who perceives them..

If a blind person wanted to study the brain of a person who can see colors to try to understand what he means when he talks about colors, he could carry out a whole series of investigations until he obtained a complete description of the laws of color. wavelength processing. You could try to completely decipher the laws of color vision. However, despite having all this information, I still would not know what red is or what blue is, because they are part of the real and ineffable experience of color (indescribable). Therefore, color is a qualia, that is, color is an intuitive, immediate and indescribable knowledge, it is a personal and unique experience, for all that it evokes us, that is why it is an intrinsic and direct process..

Dennett talks about vision as follows:

“We do not see, hear or feel the complicated neural machinery churning in our brain and we have to settle for an interpretation, a digested version, an illusion of the user, which is so familiar to us that we take it not only as real but as reality. most undoubted and intimate of all ".

Ineffable? In the strict sense of the unnameable, perhaps no more, all thanks to the technology that shows us today that even with achromatopsia, colors can be communicated or learned, through direct experience, although in ways that perhaps we never imagined, all thanks nanotechnology and cyborgs. If this sounds like a science fiction movie to you, read on and you will see that reality is even more interesting and promising.

Colors and emotions

Most of us human beings are highly visual, an aspect that is being very well used by neuromarketing and marketing with excellent results for several decades..

Colors express states of mind and emotions of very specific psychic significance, they also exert a physiological action. For example: In general, warm colors are seen as uplifting, happy, and even uplifting; colds are generally perceived as relaxing, concentration inducing and tranquilizing, in some cases depressing. Let us remember that vision involves perception and our context, as well as personal preferences, so they are also determined by their unconscious reactions, as well as by various associations that are related to their environment..

Colors evoke certain emotions, at least in most, because we remember that color is a subjective and personal experience. For example: Yellow, in most cases, is a stimulating color, it is like a radiant light, many associate it with solar energy and its benefits, it represents joy and is stimulating. Red is related to blood and fire, it suggests heat, excitement, passion, drive, action, success and aggressiveness. Blue is the color of the sky and water for many it evokes serenity, concentration and coldness. Orange, being a mixture of yellow and red, has the qualities of these, that is why it is very helpful in shops that have to do with the food industry, because it invites customers to consume the food product, through the stimulus that gives us the color. Green, a color very present in Mother Nature, is usually perceived as fresh, natural, calm and comforting. Violet is a color that we associate with questions of magical and mystical thought; in their light shades they express delicacy and tranquility. Likewise, each color has its own social construct and therefore is linked to the processes of sensation, perception, emotion and can even produce physiological reactions..

Links

  • http://micro.magnet.fsu.edu/primer/lightandcolor/humanvisionintro.html
  • https://www.ncbi.nlm.nih.gov/books/NBK1418/
  • https://ghr.nlm.nih.gov/condition/achromatopsia
  • https://ghr.nlm.nih.gov/gene/PDE6C
  • https://ghr.nlm.nih.gov/gene/CNGA3
  • https://ghr.nlm.nih.gov/gene/GNAT2
  • https://ghr.nlm.nih.gov/gene/CNGB3
  • https://ghr.nlm.nih.gov/gene/PDE6H
  • https://ghr.nlm.nih.gov/condition/color-vision-deficiency
  • https://aapos.org/terms/conditions/10

Bibliographic references

  • Carlson, N. (2006). Physiology of behavior. Madrid: Pearson Education.
  • Coren, S., Ward, L. and Enns, J. (2001). Sensation and perception. Mexico: McGrawHill.
  • Dr. Oliver Sacks, Island of the Color Blind. Alfred Knopf editor. USA: Vintage Press Editor.

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