Reading and Dyslexia in Deaf Children

Many deaf children have reading difficulties but there are no reading tests designed specially for deaf children.

Research at City University London will produce scores for deaf children in Year 6 on a number of deaf-friendly reading tests.

This will hopefully be the first step in developing a standardised reading test for deaf children which teachers may use in the future to check on the reading progress of deaf children in their class.

As part of the same project, they are investigating dyslexia in deaf children which is currently difficult for teachers to spot.

This means that deaf children with dyslexia are not identified and cannot benefit from the specialist help that other dyslexic children receive.

The first stage has focused on the reading skills of deaf children who use spoken language.

The next stage of the research will look at deaf children who use British Sign Language (BSL) to communicate.

There is no written form of BSL and so deaf signers face completely different challenges when learning to read English.

Children and families who take part in the project will be contributing to a bank of data which we hope will help deaf children in the future receive the help they need at school.

Participants will also be provided with a summary of the project's overall findings at the end of the study.

The project is being run by Ros Herman, Penny Roy, Fiona Kyle and Catherine Barnett with funding from the Nuffield Foundation.

Hearing Disability Linked To Poor Touch Sensitivity

Touch and hearing are very distinct, but German scientists have found a possible genetic link between the two sensory systems.

Superficially, the two senses might seem worlds apart, but both rely on the ability to translate motions - vibrations in the ear and movement and pressure on the skin - into signals to the brain. A common set of molecules or mechanisms might be at work.

To determine if touch sensitivity can be inherited genetically, Henning Frenzel of the Max-Delbruck Center for Molecular Medicine and his colleagues first examined 100 pairs of fraternal and identical twins in a study outlined in the journal PLoS Biology.

They tested the twins on two kinds of touch sensitivity traits: "vibration detection threshold," or how low a vibration the subject could detect with their pinky finger; and "tactile acuity," or the ability to distinguish between two pressure points on the skin that are very close together.

Since the identical twins are genetically identical and the fraternal twins share up to 50 percent of the same genes, any genetic effect on touch should be more pronounced in the former.

Next, Frenzel and his team calculated the heritability of the two traits, a figure that explains the degree to which genetic variation contributed to the variation in the traits seen in the subjects. On average, 28 percent of the differences in tactile acuity and 52 percent of the differences in vibration detection could be chalked up to genetic influence.

Second Experiment
In a second experiment, the scientists found that some - but not all - of a population of young people that were born deaf also had impaired tactile acuity. But since there are about 70 known genes that are involved in hearing impairment, the researchers wanted to focus on a smaller group of genes to test the link between hearing and touch impairment.

Third Experiment - Usher syndrome
The scientists next examined patients with Usher syndrome - a hereditary condition that causes both hearing and visual impairment. They zeroed in on USH2A, one of the nine known genes that, when mutated, cause Usher syndrome.

Of the Usher patients studied, the 19 individuals that had a mutation in USH2A had both impaired hearing and poor touch sensitivity. It's possible then, that this gene may play a role in both touch and sound.

"Our next task will be to investigate some of these other cases to see if they are also correlated with problems in touch," senior author Gary Lewin said in a statement Tuesday. "This will give us a better understanding of the genetic mechanisms that underlie both types of perception."

Why Current In-the-Ear Hearing Aids Fail

Hearing aids have improved greatly over recent years, but they continue to be a surprisingly frustrating experience for new wearers.

Clearly, today’s hearing aids are tiny, nearly invisible in fact, and they amplify sound and are able to present a higher range of frequencies, but they have not yet completely solved the problem of amplifying the peripheral sounds we just don’t want, or don't need to hear.

For new wearers the crumpling of a paper bag on the other side of a room can sound like a jackhammer.

This is a huge challenge for technology because it is dependent on how the brain perceives sound and how we have learned to filter peripheral sound out of normal hearing. Andrew J. Oxenham is a psychologist and hearing expert at the University of Minnesota and an expert in psychoacoustics.

Oxenham explains: The ear works by analysing sound and breaking it into different frequencies and with many forms of hearing impairment it’s this frequency selectivity that is impaired.

What that means is that the ear doesn’t filter as well as it did before. So instead of having very sharp tuning to filter out different frequencies the filtering becomes much broader and there is no real way of compensating for that.

You can’t sharpen the filters or you can’t pre-process sound so it’s sharp. It’s like a broken TV set. You can process the signal going into the TV as much as you like but you still won’t get a clear picture of the output.

Recent hearing aids have made a lot of progress, like being able to present frequencies of up to 6000 Hz as opposed to limited frequencies up to about 4000 Hz, by using digital signal processing, and a lot more computing power on a lot smaller chip.

Another big leap forward has been made with directional hearing. They can focus the microphones toward the front and filter out a lot of the sound coming from the side and back. And although that is a fairly simple technique, it involves signal processing that wasn’t possible with earlier hearing aids.

Ambient or peripheral sound is horribly distracting for hearing aid wearers. A paper bag being crumpled across a room sounds screechingly loud.

This is common complaint of people who recently start wearing a hearing aid. Their hearing has deteriorated, often without them being completely aware of it, over a period of time.

When they are suddenly fitted with a hearing aid, they hear sounds they’ve got used to not hearing. The sounds are suddenly annoying and distracting. It’s a contrast effect.

It’s more to do with perception i.e the brain’s ability to analyse and prioritise different sounds.

It’s a complex interaction between the ear and the brain. The ear sends signals up to the brain; the brain does an awful lot of processing on top of that; then sends signals back down to the ear. These signals change the way the ear accepts input.

This is partly why hearing aids are not perfect because the hearing aid is not part of that natural feedback loop. There’s no way with current aids that the brain can interface with a hearing aid directly to change its characteristics.

Hearing Loops
To deal with background noise there are things called “hearing loops.”

These are systems that are set up within places like concert halls and churches that interface directly with the hearing aid. It’s like sending a radio signal to the hearing device.

The idea is that this hearing loop picks up the sound directly from the microphone in front of a speaker.

If you are in a conference and the speaker is talking into a microphone. Normally we hear the sound acoustically through the airwaves.

If you are wearing a regular hearing aid the microphone will pick up the sounds on the airwaves but that is together with all the background noise and reverberation in the room.

With a hearing loop it sends the signal directly from the microphone to the ear and bypasses all the acoustics in the building itself. So the ear is getting a much better, clearer and cleaner signal of what’s coming into the microphone.

Two hearing aids better than One?
It’s only recently that people have routinely been fitted with two hearing aids. Often people only got one.

Directional hearing and the way we localise sound: To know where the sound is coming from the brain compares the signals coming into the two ears. So if it’s slightly louder on one side then the brain knows the sound is coming from that side.

More importantly it’s the time of arrival difference between the two ears. If you think about a sound coming from the right. The sound will reach your right ear a little bit before it reaches your left ear.

Although we are talking about millionths of seconds, your brain needs two ears to make a distinction. If you only have one you lose that ability to localise sound and tell which direction it is coming from.

It’s also an important part of filtering out sound and noise. The brain can determine if there is speech right in front and background noise in back of and to the side. The brain can use those differences in localisation to help to make the speech more intelligible.

So the biggest technical challenge is developing hearing aids that can focus on what we really need and want to listen to. This is the current problem.

The Solution
We are hoping through even more sophisticated signal processing schemes that we’ll be able to work on artificial source segregation; i.e. analysing the signal that is coming in and figuring out what is speech and what isn’t, and only presenting to the ear the wanted signal.

Distinguishing between speech and noise
The assumption is that what you really want to listen to is speech, and so there are certain acoustical aspects of speech that we can recognise and there are certain acoustical aspects of noise that are different from speech.

So, we need to establish a suitable algorithm to be able to distinguish between speech and noise that will help you towards filtering the unwanted signal.

A more complete solutiion could mean that brain-computer interface may be part of the hearing aid systems of the future. Where the hearing aid is tapping into brain responses to pick up the specific signal the person wants to pay attention to.

This is an ongoing process with incremental steps and we will continue to see improvements over the next 15 years.

Total Hearing Aid Implant

A University of Southampton diagram of the UK's first totally implanted hearing aid.

The Otologics 'Carina' middle ear implant device consists of a rechargeable battery, a signal processor and a microphone which are all implanted under the skin.

Picture: University of Southampton

Word learning better in deaf children who receive cochlear implants by age 13 months

Word learning better in deaf children who receive cochlear implants by age 13 months

A growing body of evidence points to the importance of early auditory input for developing language skills. Indiana University Department of Otolaryngology researchers have contributed to that evidence with several projects, including their study involving 20 deaf children (22- to 40-months-old and 12 to 18 months after cochlear implantation) and 20 normal hearing children (12- to 40-months of age) that was presented Feb. 21 at the AAAS meeting.

The study's principal author, Derek Houston, Ph.D., associate professor and Philip F. Holton Scholar at the IU School of Medicine, said the study found that deaf children's word-learning skills were strongly affected by their early auditory experience.

"This research is significant because surgery at very young ages requires more expertise," said Dr. Houston. "It is important to know if the increased benefit of early auditory input warrants surgery at younger ages."

Currently, the Food and Drug Administration guidelines approve cochlear implantation at one year of age, although many children are implanted as young as 6 months of age.

Dr. Houston said the research showed that deaf children's word-learning skill was strongly affected by their early auditory experience, whether that experience was through normal means or with a cochlear implant.

Children who received the implant by the age of 13 months performed similarly to their normal-hearing counterparts while children who received a cochlear implant later performed, on average, more poorly than their normal-hearing peers.