September 21, 2012
Bilateral Cochlear Implants Possibly Aid Binaural Sound Processing
Connie K. Ho for redOrbit.com — Your Universe Online
Researchers from the Stanley Steyer School of Health Professions at Tel Aviv University (TAU) and The Hearing, Speech, and the Language Center at Sheba Medical Center recently noted that bilateral cochlear implants could possibly improve binaural sound processing in the brain.
Cochlear implants, sometimes known as bionic ears, have been used since the end of the 1980 as electronic devices in both ear lobes. They were created to help in boosting the hearing of people who were deaf or hard-of-hearing. The study by TAU showcased how the brain could process the sounds from each ear at the brainstem through “binaural processing.” Binaural processing allows for sound localization, the ability to understand speech in a noisy environment, and an easier way of listening.
"When we hear with both ears, we have an efficient auditory system," explained Dr. Yael Henkin of TAU in a prepared statement.
According to the Gibson Herald, cochlear implants function as an external speech processor. It can send a digital signal to the internal implant by changing the original sound. The hearing nerve is then stimulated by electrodes, sending out signals to the brain and sound to the wearer of the implant. With cochlear implants, less sound information is received and processed by the brain than would be done with a hearing aid.
The researchers at TAU studied children who had not been born deaf, but who had lost their hearing early on at a young age. The patients who could complete binaural processing were the few who had bilateral cochlear implants. Those who had first received cochlear implants at a young age and then a second pair long after did not have the same skills of binaural processing.
In the study, the team of investigators explained how the two ears work together in creating a complete, unified reception of sound for individuals. The two ears could integrate information and help locate the source of different sounds, so that people could tell the difference from one sound to another.
Participants had to listen to syllables “ta” and “ka” and were required to press a button upon hearing the syllable “ta.” These sounds were sent to the left ear, the right ear, as well as both ears at the same time. At the same time, the scientists studied the brainwave P300, which is linked with auditory discrimination. They discovered a binaural interaction component by comparing the P300 brainwaves during the time at which both ears were stimulated separately and also the time at which the ears were stimulated together.
Based on the findings, a binaural component was found with individuals who had not been born deaf but who had been given bilateral implants early on. Participants who had only one implant for a number of years did not have binaural processing. They believe that, if there is a long duration of auditory deprivation, the implants cannot completely restore hearing.
“Auditory experience prior to cochlear implantation is critical for binaural processing," noted Henkin in the statement.
The researchers hope that, in the future, the implants will be designed in such a way that they can synchronize with one another and provide patients the necessary elements to have binaural processing.
The study was recent published in the journal Cochlear Implants International.