Label the diagrams below
Write NO MORE THAN TWO WORDS for each answer
Questions 35 – 40
Complete the summary below.
Write NO MORE THAN TWO WORDS for each answer
You will hear a lecturer giving a talk on cochlear implants. First you have some time to look at questions 31 to 40.
Now listen carefully and answer questions 31 to 40.
The topic for today’s lecture is cochlear implants, which are a relatively new form of technology for assisting people who are profoundly deaf.
First, let’s revise how normal hearing works. If you look at image 1, you will remember that the ear has three sections. The outer ear, or pinna, picks up sounds, which are then channelled through the ear canal to the eardrum, where they are transformed into mechanical vibrations. These are sent to the cochlea, or inner ear. Inside this snail-shaped tube, there are sensory hearing cells that have a variety of functions. The outer hair cells make soft sounds louder, and reduce the volume of louder sounds. The inner ear cells transfer this information to the auditory nerve, and thence to the brain, which interprets the input as sounds. This sophisticated and sensitive process allows us to process a huge variety of auditory input. For those who are profoundly deaf, the system functions poorly or not at all, and the brain does not receive the input it needs to process and interpret sounds.
Image 2 shows how a cochlear implant works. You can see that the implant has three main parts. The first, external part, behind the ear itself, is the microphone and, at the back of this, you can see its associated speech processor, which is a tiny computer. This analyses and digitises sounds and sends them to the transmitter, which is worn on the head. Those sounds need to be converted into electrical impulses so that they can be sent to the cochlea. If you look carefully at the image, you can see that just under the skin, directly behind the transmitter, is a surgically-implanted receiver. This receives the sounds from the transmitter. It converts these sounds into electrical impulses, which are sent directly to an electrode array that is implanted inside the cochlea itself, thus completely bypassing the ear canal.
As you have seen, a cochlear implant does not operate in the same way as the ear, nor, in fact, as a hearing aid. In cases of mild hearing loss, hearing aids can be very helpful. They simply amplify the normal sound waves as they travel down the ear canal. However, they generally cannot overcome severe hearing difficulties, and this is where cochlear implants come into play. So, what are the pros and cons of using a cochlear implant?
Well, firstly, cochlear implants can deliver significant improvements in hearing for some users, and some people report dramatic improvements in the perception of individual words and sentences over the weeks and months after an implant. However a cochlear implant is not a magic bullet that works equally well for all users. The sound signals that the brain receives from an implant are quite different from normal ones, and this means that the user has to relearn how to hear. Many users report that speech sounds robotic after a cochlear implant, and the degree to which people can adjust to this new kind of hearing varies hugely with each user and situation.
It is important to understand that a cochlear implant is not a cure for deafness, and that the user is still deaf. Especially for a child, an implant is a long-term commitment, involving lengthy and intensive training. The user must learn to reinterpret sounds, and will likely need to augment this with speech therapy, so that people in the community can easily communicate with them. The implants work much better in quiet situations than in noisy ones, so they still need to learn to lip-read and to use sign language. The surgery itself is not without risk, though it has greatly improved since it was first performed, and there is some possibility of damage to facial nerves. Another disadvantage of a cochlear implant, is that the surgery may remove any natural hearing that the deaf person still retains. This takes away the possibility of using a hearing aid should the implant not be effective. For this reason, many users have implant surgery performed on only one ear, the one with the least natural hearing.
So, who is best suited to receiving an implant? Many factors impact on this decision. The most significant one appears to be the duration of the deafness, and, as you would expect, those who have been deaf for a long time generally have lower success rates. The second, related factor is how old the patient was when they became deaf, and maybe more significantly, whether they had learned to speak before they became deaf. Those who become deaf post-lingually generally have better outcomes. Another factor is the health and structure of the cochlea, and how many nerve cells the user retains. This is related to the cause of the hearing loss, and recent research is exploring how the spiral ganglion, or nerve cells are affected by disease. OK, let’s now move on to discuss the long-term prognosis for …