A Stanford neurobiologist teamed with child-development specialists at the University of Maryland to see if children with cochlear implants were able to meld their newly acquired hearing capability with their ability to read lips. In other words, did their brains process speech the same way as people who are born with the ability to hear?
In the Dec. 5 online edition of the Proceedings of the National Academy of Sciences, the researchers discuss how they used a simple auditory test and found that some children with cochlear implants fuse the visual and auditory aspects of speech - just like people with normal hearing. But the effect was only seen in children who received their implants before the age of 30 months, adding to the body of evidence suggesting that the earlier a hearing-impaired child receives a cochlear implant, the better.
"I see this as a fascinating experiment that reveals the tremendous capacity for plasticity in the developing brain," said Eric Knudsen, PhD, the paper's senior author and the Edward C. and Amy H. Sewall Professor at the Stanford University School of Medicine.
Most people don't appreciate that speech is a product of both hearing and vision, explained Knudsen, who is also chair of Stanford's Department of Neurobiology. The brain has learned that in conversation, the lips and face make certain gestures that always occur together with certain sounds. "The brain is always combining what it sees with what it hears and making the best guess at what was said," he said. In most situations, hearing speech alone is just fine - that's why we can talk on telephones. But in noisy situations, when hearing is poor, our brains rely heavily on lip and facial movements to figure out what someone is saying.
Knudsen has a long history of studying the abi
Source:Stanford University Medical Center