Future Foresees Eyes In the Back of Your Head

A "blind" tadpole without its native, normal eyes is able to see using a functioning ectopic eye located on its tail.
D. Blackiston and M. Levin

Having eyes in the back of one’s head has long been the threat of mothers everywhere. But for future generations, that ability may become real. Not only could we have eyes in the back of our head, we could have them on our arms, our shoulders -– even our derrières.

For the first time ever, scientists have shown that eyes transplanted far outside the head in a vertebrate animal were capable of “seeing,” despite having no direct neural connection to the brain.

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This discovery has many implications, especially in the fields of regenerative medicine, sensory augmentation research and bioengineering, say biologists at Tufts University School of Arts and Sciences.

“One of the things that this study showed us is that connecting a sense organ as complex as the eye to the spinal cord is sufficient to confer vision,” Dr. Michael Levin told Discovery News. “So you don’t have to plug in to the actual brain.”

Levin is a professor of biology and director of the Center for Regenerative and Developmental Biology at Tufts University. Along with Douglas Blackiston, a post-doctoral associate in Levin’s lab, the two co-authored the study “Ectopic Eyes Outside the Head in Xenopus Tadpoles Provide Sensory Data For Light-Mediated Learning,” recently published in the Journal of Experimental Biology.

For the experiment, biologists surgically removed the eyes of donor tadpoles and grafted them onto the posterior of recipient tadpoles, which induced the growth of ectopic -– or abnormally placed –- eyes. Recipient tadpoles had their natural eyes removed, so only the ectopic, spinal cord-connected eyes remained.

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The team developed a computerized visual training system with quadrants of water illuminated by either red or blue LED lights. Administrators issued a mild electric shock to tadpoles swimming in the red quadrant and used a camera-equipped motion tracking system to record the tadpoles’ subsequent movements.

More than 19 percent of the tadpoles with optic spine-connected nerves showed that they had learned to swim away from the red light. Tadpoles in the blue light swam naturally.

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