Associate Professor of Biology John Kirn has spent a considerable number of years studying the brains of birds. Currently, along with several Wesleyan students, including Amy Kim ’04, Eve Harrison ’04 and Yi-Lo Yu, a fifth year graduate student, Kirn is researching the unusual capacity of songbirds to replace neurons that directly control motor function. Although very different, his results have important implications for the study of human brains as well.
Kirn began studying birds as a graduate student in 1982 at Cornell. He was originally trying to see how sex differences develop in zebra finches. Eventually he became interested in the ways in which these birds replace brain cells that have died.
Although neurons are regenerated throughout a bird’s life, its song remains relatively constant. However, somehow the brain preserves information while it is continually regenerating itself.
Another aspect of Kirn’s research concerns the implications of these findings. If a bird’s new brain cells are “taught” the information already stored in its brain, perhaps it is possible to restore the lost information in a human brain by adding new neurons.
To explore these questions, Kirn and his team have set up experiments using zebra finches and canaries. The advantage of these birds is that they have regenerative brain cells linked directly to their ability to sing (only neurons from certain areas of the brain work this way). Singing regulates the addition of new neurons, the production of which conversely helps the birds to learn new songs and continue singing old ones.
Kirn wondered what happens to the song of deafened birds, asking if the brain compensates for the changed experience of birds that can no longer hear.
The scientists first deafened adult birds and then injected them with markers that indicated the number of neurons being produced in a given area of the brain. They found that hearing and deaf birds do indeed have different neurological processes. Hearing birds have a high turnover rate of neurons that control song, while deaf birds retain their neurons for much longer. Thus, their song is “hardwired.” Since they cannot relearn as easily, they preserve the information they already have.
Kirn and his team are exploring their research and the opportunities it has given them. Most recently, they brought their findings to the Annual Society for Neuroscience in New Orleans.
He believes that reproducing the neuron replacement in birds for humans could be effective in ways that stem cell replacements are not. His innovative experiments have won him the attention of the magazine New Science and The Hartford Courant.
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