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In detail

Achromatopsia: seeing a gray reality, without being pessimistic

Achromatopsia: seeing a gray reality, without being pessimistic

The perception of color a purely subjective and personal experience.

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

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

Content

  • 1 All sensory experience is subjective
  • 2 How is vision given?
  • 3 What is achromatopsia?
  • 4 Genetics and achromatopsia
  • 5 Cerebral achromatopsia
  • 6 Diagnosis and treatment
  • 7 Colors and emotions

All sensory experience is subjective

The perception of color is a subjective experience lived in each person in a unique way, one could say that color is a quality. For the eye sees and the brain interprets the seen.

Experiences are subjective and science defines them as a residual side effect., that is, they are reducible to the processing of the information and anatomical structure of each organism. The view is a very valuable sense, because through this sense we can perceive and access the information that is in our environment. Therefore, Aristotle said that: "we come to 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 eyesight It occurs through the path of light through the inside 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, aqueous humor and 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, because these cells transmit visual signals from the eye to the brain through this process. The canes provide vision in low light conditions (night vision). And the cones provide vision in bright light (daytime 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 around us, making it unique in each individual.

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

Other ganglion cells that receive the input of the colors do not respond differentially to the different wavelengths, limiting themselves to encoding relative luminosities in the center and the periphery. These cells serve as black and white detectors. Likewise, they encode the information on the relative amount of light that enters the center and the periphery of its receiving fields and frequently, on the wavelength of that light. The striated cortex and the visual cortex of association perform the additional processing of this new visual information that is received from the magnocellular, parvocellular and coniocellular layers of the dorsal lateral geniculate nucleus. Thus, The role of striated cortex in color analysis is essential 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 color perception and small details, receives information only from the red and green cones. The neurons of the striated cortex send axons to the extra-striated cortex (region of the visual cortex that surrounds the striated cortex).

Studies with laboratory animals indicate that the neurons of a specific sub-area of ​​the extra-striated cortex: V4, are involved in both shape analysis and color analysis. The lesions of the V4 area suppress the constancy of the color referred to the precise perception of the 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 them some degree of color discrimination, it is also known as color blindness. These vision problems develop in the first months of life, when it is not a consequence of another detonating event.

It also involves other vision problems, such as: increased sensitivity to light and glare, known as photophobia; involuntary eye movements (nystagmus); in some, 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 all over the world. Complete achromatopsia occurs frequently in the population of the inhabitants of Micronesia, since between 4 and 10% of people in this population have a total absence of color vision, in that population mutations have been found in the gene CNGB3 Mutations in the NGA3, CNGA3, CNGB3, GNAT2, PDE6C and PDE6H genes are found in the world population.

Is a autosomal recessive disorder, which means that for the disease to develop, the two 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 of 4) risk for each pregnancy. There would also be a 50% chance that the child will be a carrier.

In people with complete achromatopsia, the cones are not functional. The loss of the 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 no mutations in the genes that commonly affect the other population with achromatopsia have been identified. In these individuals, the cause of the disease is unknown. Other genetic factors that have not been identified and probably contribute to this condition.

Proportion of pathogenesis detected by this method

GENPROPORTION OF ACROMATOPSY ATTRIBUTED TO PATHOGEN 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
UnknownFamiliesDoes not applyNo reports

Achromatopsia it is inherited in an autosomal recessive way. In conception, each brother 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" tests for at-risk relatives and prenatal tests for higher-risk pregnancies are possible if pathogenic variants have been identified in the family.

Cerebral achromatopsia

Achromatopsia is one of the specific visual disorders of cerebral origin, which implies the specific loss of the ability to see the world in colors. Those who suffer from it usually perceive a monotonous world, mainly in terms of color, because the colors as I mentioned, they can produce emotions and modify our perception at times, some patients describe their vision as "dirty shades in grayscale", 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 so much light, which gives them excellent nighttime visual skills or when there is low light, such as fishing for certain species, which is best done at night, because “look better in shadows" Proving so even though 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, studies of functional magnetic resonance imaging in humans (fRMN) show that there is a color sensitive region in the inferior temporal cortex: V8. Lesions that cause achromatopsia or colorless vision are injured in the V8 area or other brain regions that provide V8 interference. In addition to losing color vision, people affected by this injury cannot even imagine colors or remember those of the objects they saw before brain damage occurred.

Other visual disorders of cerebral 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. Passive Chromatopsia: A single case study revealed the case of a 54-year-old man who suffered repeated attacks which were accompanied by a sudden and temporary 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 ventral lesion.

Diagnosis and treatment

It is established through clinical and family history, exams 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 other.

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

Common treatment for achromatopsia

Dark and highly specialized filter crystals are used as contact lenses with red scales to reduce photophobia, to enhance and improve visual acuity; special graduation for reduced vision; It is advisable to have an ophthalmological exam every 6 to 12 months in children who suffer from it and every two to 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 whatever we can when they require it and it is in our possibilities.

What we see is not what it seems

"In this world nothing is true, nothing is a lie, everything depends on the glass with which you look". Popular saying

The things and colors we perceive are not exactly as we 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 types of qualities. The primary, which are inseparable from a body, regardless of its state, which we they produce simple ideas, such as solidity, extension, figure, movement or rest and size, that is, that knowledge can be expressed in mathematical terms. Instead, the secondary qualities, they are those that do not exist in the things themselves, and, in a sense, are subjective, such as heat, color, sounds and taste, because these sensations depend on the subject that 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 speaks of colors, he could carry out a whole series of investigations until he obtained a complete description of the laws of Wavelength processing. I could try to completely decipher the laws of color vision. However, and despite having all this information, I still wouldn't know what red is or what blue is, because they are part of the real and ineffable experience of color (indescribable). Therefore, the color is a which one, that is, color is an intuitive, immediate and indescribable knowledge, it is a personal and unique experience, for all that it evokes, that is why it is a intrinsic and direct process.

Dennett, talk about the vision as follows:

“We do not see, hear or feel the complicated neural machinery turning 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 indubitable and intimate of all ”.

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

Colors and emotions

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

It may interest you:Psychology of color and function of colors in Chromotherapy

The colors express moods and emotions of very specific psychic significance, they also exert a physiological action. For example: In general, warm colors are considered as stimulants, cheerful and even stimulants; Colds are generally perceived as relaxants, concentration inducers and tranquilizers, in some cases depressing. Recall that the 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.

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

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Links

Bibliographic references

  • Carlson, N. (2006). Behavioral physiology. Madrid: Pearson Education.
  • Coren, S., Ward, L. and Enns, J. (2001). Sensation and perception. Mexico: McGrawHill.
  • Dr. Oliver Sacks, The island of the blind to color. Alfred Knopf editor. USA: Vintage Press Editor.
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