The auditory and visual aspects of speech can be processed much faster by the brain of a child which has a hearing impairment, if the cochlear implant is carried out at an early age, according to a study conducted on cochlear implants. About 36 profoundly deaf children aged between 5 years and 14 years were studied in the research. These children had received the cochlear implant for a period of one year. The research was aimed at seeing to what extent children with the implants were able to meld their newly acquired hearing capability with their ability to read lips.
The findings showed that the children fully able to merge the visual and the auditory effects of speech were those who had received their implants before they were 30 months old.
Eric Knudsen, PhD, the paper's senior author who headed the study along with Nathan Fox, PhD, Director of the University of Maryland's Child Development Lab, said that what people often fail to realize was that speech is a product of both hearing and vision. He added that the brain is constantly combining both the visual and the auditory aspects to come up with what is being said.
The brain always tries to combine what it hears and sees and makes the best possible judgment as to what was spoken, according to the researchers. One of the tests that were conducted was what is known as the McGurk effect. In it a listener is presented with an audio recording of a single syllable while watching a synchronized video of a speaker's face mouthing a different syllable. In most cases, this combination of the non-matching audio and visual information causes the brain to hear a completely different third syllable.
"The McGurk effect is so amazing because it demonstrates clearly that speech is not just what you hear. If I thought I heard 'ba' but the lips look like they are mouthing 'ga' then it must have been 'da. It is impossible to hear the proper sound while viewing the speaker's lips," Dr Knudsen added.
The study showed that those children who received the implant after they had crossed the 30 month age mark, relied solely on the movement of the lips, and reported that the sound they heard was the syllable being mouthed. They thus showed little evidence of the McGurk effect.
Dr Fox said that the study proved the importance of early experience on brain development and behavior. But there is not much empirical data in humans demonstrating the importance of early experience on brain development and, according to Dr Fox. (ANI)