The ferrets whose eyes were wired to be ears

In an effort to test the plasticity of the brain, scientists a decade ago decided to scramble a ferret's brain so that its eyes were hooked up to its auditory cortex. So clearly the ferret was blind, right? Wrong. Find out about the experiment that lead scientists to understand exactly how adaptable our brains can be.

There are some experiments that lead you to believe that certain areas of science should be called "Practical Frankensteinology." This type of science happens when biologists do something incredibly cool, a little bit creepy, and ultimately useful. In this case, they decided to hook a ferret's eyes up to its auditory cortex. They chose ferrets because ferrets' brains develop much like human's brains, except ferrets brains do much of their developing outside of the womb. At the time, people were still mulling over exactly how adjustable human brains were. Only a little earlier it was thought that a brain 'crystallized' at birth, and didn't restructure itself past then. When evidence began surfacing that people continued making new neurons throughout their life, researchers wanted to see if the brain could change its function as well as its form.

First scientists destroyed the auditory nerve on one half of the ferret's brain. They knew from experience that, if the auditory nerve was taken out, the optic nerve would grow into the region where it went. Once the optic nerve was in position, they looked at the brain itself. Neurons in the auditory region of the brain generally line up in rows. Neurons in the optic region form pinwheels. The re-wired part of the brain arranged its auditory cortex in pinwheels. Clearly something strange was happening in there.

In time, and with experimentation, they found that the auditory cortex became the ferret's visual cortex. Although it was less sensitive than the actual visual cortex on the control side of the brain, it lit up with activity when the ferret saw lights. The modified auditory cortex also helped create mental maps by which the ferrets navigated the world. Despite being a part of the brain never, in normal biology, used for such a thing, the auditory cortex quietly and accurately took over visual function. The ferrets were seeing with the wrong part of their brain, but they were seeing all the same.

Via Journal of Neuroscience and University of Washington.