A Different View of Color Vision Development

In summary: Color vision depends upon having different photoreceptors that maximally respond to different light frequencies. The brain then recombines the the different color inputs into the color imagery that most of us are familiar with.In summary, the study found that by manipulating thyroid hormone levels, it is possible to change a person's color vision. This could be useful for treating conditions like color blindness.
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BillTre
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I ran across an interesting little article in a trade mag e-newsletter.
I tracked down the original research article, which is sadly pay-walled-in.

Color vision depends upon having different photoreceptors that maximally respond to different light frequencies. The brain then recombines the the different color inputs into the color imagery that most of us are familiar with.
There are many fun vision tests that can diagnose vision deficits, some of which I used to have on my i-Pad (now gone). (I consider them fun because knowing how they work, I can often guess the answer for particular color blind conditions.) They are usually interpreted as to which of the color pigments in the photoreceptor cells are lacking, usually indicative of a particular genetic deficiency.

This study I discovered, has found a different way to make distort the usual mix of differeent photorecptors sensitive to different colors.
Turns out that during retinal development (in humans), retinal photoreceptors maximally sensitive to different colors develop in a sequence (first blue, then red, then green; sequencing is not too surprising) and that the changes in which cells develop is controlled by Thyroid Hormone (TH). This mechanism was confirmed by treating human retinal organoids in culture with different levels of TH so only particular color sensitive classes of photoreceptors developed. Organoids are one of the few ways to do actively manipulative human biological studies that is considered ethical.

In this way, it is proposed that TH could affect color vision without affecting the genetics of the photorecptor pigments. For example derangements of maternal TH production could lead to unusual color vision in infants.
In addition, TH is most active when it has 3 iodine atoms (T3) bound to it and less so in the T4 form. T0, T1 and T2 not so active. They bind to the TH receptor in induce actions in different cells that have the TH receptor in their surface.
Lacking the TH receptor also affects color photoreceptor development, as I might guess would iodine deficiencies and selenium deficiencies (selenium is part of another enzyme which regulates the iodine levels in TH).

Normally TH's signally function is thought of a general regulation of metabolism in a variety of ways, but it is also the trigger for metamorphosis in amphibians (tadpole to frog transition) and (some people claim) humans also.
Significant parallels can be drawn between frog metamorphosis and mammalian birth (Tata, 1993, Wada, 2008). Both frogs and mammals undergo a life history transition from aquatic (amniotic fluid or water) to terrestrial habitat with air-breathing and lung maturation, during which they (1) transition to a new food source accompanied by the maturation of the intestine to the adult form, (2) switch from the fetal or larval to adult type of hemoglobin, (3) increase production of albumin and other plasma proteins, (4) induce urea cycle enzymes in the liver, (5) undergo skin keratinization, (6) have limb elongation, and (8) experience developmental progression and restructuring of the central and peripheral nervous systems.
Also, important changes in the fetal blood circulation (such as shifting blood flow away from the placenta to the lungs) occur just prior to/during/after birth.
 
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1. What is color vision development?

Color vision development refers to the process by which an individual's ability to perceive and distinguish colors develops over time. This development is influenced by both genetic and environmental factors.

2. How does color vision develop in infants?

In infants, color vision development begins in the womb and continues to develop in the first few months of life. At birth, infants are able to perceive basic colors such as red, green, and blue, but their ability to distinguish between different shades of these colors continues to improve as they grow.

3. What factors can affect color vision development?

Genetics, age, and exposure to different colors and patterns can all play a role in color vision development. Additionally, certain medical conditions or medications can impact an individual's ability to perceive colors.

4. Can color vision development be improved?

While color vision development is largely determined by genetics, there are some interventions that can help improve color perception. For example, vision therapy exercises and color vision training programs have been shown to be effective in improving color vision in individuals with color vision deficiencies.

5. Are there any long-term effects of delayed color vision development?

In most cases, delayed color vision development does not have any long-term effects on an individual's vision. However, in rare cases, it can be a symptom of an underlying medical condition that may require treatment. It is important to consult with a medical professional if you have concerns about your color vision development.

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