Researchers from Duke University Medical Center in the US have studied male zebra finches to find out how hearing loss may affect the parts of the brain that control vocalisation. Songbirds differ from most animals in that the males' mating songs disappear when they lose their hearing.
The researchers found that portions of a songbirds brain that control how it sings began to decay within 24 hours of the animal losing its hearing.
“When hearing was lost we saw rapid changes in the areas that control song, the bird's equivalent of speech,” said Richard Mooney, Ph.D and professor of neurobiology at Duke University Medical Center.
Nerve cells visibly changed
The researchers used a protein from jellyfish that can make songbird's nerve cells glow bright green when viewed under a laser-powered microscope. Through this method, they were able to determine that deafening triggered rapid changes in the tiny connections between the nerve cells.
As the size and strength of the nerve cell connections visibly changed under the microscope, the researchers could even predict which songbirds would have worse songs in the coming days.
“I will go out on a limb and say that I think similar changes also occur in human brains after hearing loss, specifically in Broca's area, a part of the human brain that plays an important role in generating speech and also receives input from the auditory system,” Richard Mooney said.
The study has been published in the online version of the journal Neuron.