University Study Shows Blind Tadpoles See With Grafted Eyeballs


In an amazing feat of science, scientists have shown, even without a direct neural connection to the brain, a vertebrate can have vision through transplanted eyes located in other parts of the body other than the head. Researchers at Allen Discovery Center at Tufts University have enabled blind tadpoles to see with eyes grafted onto their tails.

Transplanting an eyeball and having it work is undeniably a daunting task, not only having it sit inside the eye sockets, nerve connections have to be attached to the central nervous system through the delicate optic nerve.

According to a research published recently in Nature Regenerative Medicine, the need to attach eyeball nerve endings to the optic nerve may not necessarily be a major obstacle at all. The research suggested that the eyes, or perhaps any other sensory organs, can be attached to any available central nervous system acting as a port and if manipulated correctly, boot the eyeball right up, Popular Science reported.

The report indicated that the project's corresponding author Michael Levin is not new to body manipulations. Last year, his work on re-wiring frogs to have them grow extra limbs were featured in Popular Science, a feat one day believes can be applied to the human body.

The latest study, led by post-doctoral associate Douglas Blackiston and contributed to by undergrad Vien Khahn, inquires how electrical signals can be adjusted to push the body to accept a new anatomy. However, when the scientists grafted eyes onto blind tadpole's tails, it began to work after a little intervention.

In a previous study, it showed that by managing the electrical state of the eyeball's new environment, the scientists were able to stimulate nerve growth and activity. However, they find a vision for the transplanted eye remains lousy.

The new study revealed the researchers took new information about how cells react to electrical signals around it. By replacing the neurotransmitter serotonin with nearby cells, and "hacking" the system, they were successful by using a migraine medication.

Levin points out that the advantage of this is that, there is an abundance of neurological and cardiological toolkit of drugs, which they say are a tremendous resource for regenerative medicine. The next step was identifying which serotonin receptor is involved and found a drug that humans take that activates it.

Accordingly, 57 percent of the tadpoles with grafted eyes were able to see and follow motion. What surprised the researchers is that the brain was able to process visual input from another spot correctly. It does, however, raise a question how the brain recognizes it as a visual information.

Levin adds their work could have weird applications in elective bioengineering. He envisions people modifying their biology beyond the standard human anatomy. People may want more eyes or different kinds of eyes, they might want to live on Mars or underwater and he said the brain would need to adjust to that.

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