- Published on 25 March 2014
Recently the insight has grown that rehabilitation of audibility in children does not lead to the same level of comprehension of speech as it does in adults. This goes especially for noisy situations. The adult’s brain processes are better capable of filling in gaps in audibility. This is an important fact for auditory training of children with hearing aids, ARC program lecturer Jessica Sullivan Ph.D. underlines. “Comprehension of speech in hearing impaired children is my motivation.” She will be giving the lecture Hearing aids and the brain: bridging the gap between audibility and comprehension for little ears .
“My starting point is the aural rehabilitation and auditory training of children with hearing aids, aimed at improved speech perception in noise”, Sullivan explains. She is Assistant Professor in the Department of Speech and Hearing Sciences of the University of Washington (WA). “It turns out that a lot of auditory training research is conducted on children with cochlear implants, but there is little recent research about children with hearing aids.””
There is emerging evidence on improved sound quality and features like digital noise reduction and directional microphones in hearing aids on speech intelligibility in children with hearing loss. Sullivan: “Only recently we have evidence that indicates that some hearing feature benefits to children are not the same as in the adult population.”
The explanation may lie in cognitive factors, which are better developed in adults. Kids just don’t have as much experience with language and are still developing more complex auditory skills well into adolescence. Sullivan: “Speech is a very redundant system. When fragments are cut out in noisy environments, adults are able to put these together and fill in the gaps thanks to their experience; they have better ability to ‘glimpse’. So my starting point was not to assume that children will perform the same as adults on speech recognition in noise – this is only the case above age eleven. The comparison of children with adults is one of apples and oranges.”
Improving speech reception is tightly linked to comprehension. One of the links is the auditory working memory, Sullivan states. “It turns out that normal hearing children, when they are confronted with a signal-tonoise ratio of -5 dB during test situations, show a reduced working memory function. Hearing impaired children experience the same amount of reduction in working memory. What we need to know is how this affects their everyday life.”
The effect of training
These notions put together led Sullivan’s thoughts in a certain direction: “One, the explanation for less comprehension of speech in children lies in a lack of experience with language. Second, normal hearing children with a deteriorated signal-to-noise ratio, like hearing impaired children, show an even larger gap with adults when it comes to their auditory working memory function. Could training make up for the lack of experience and strengthen this vital working memory function?”
Sullivan is therefore curious about how the performance of these children with all kinds of auditory training will work out. “I can say something on computer based auditory training with interrupted noise. After training hearing impaired children show not only an improvement on comprehension of speech in interrupted noise, but also a similar improvement in continuous noise. Furthermore, this improvement not only generalized to other noise types but is maintained at least three months after the training.”
Sullivan’s research, as the whole series of lectures of the Academy Research Conference during AudiologyNOW! 2014, witnesses the growing attention for the brain in hearing research and hearing care. “Ultimately it is the bridge between hearing aid technology and the brain which defines the overall understanding of speech performance of hearing impaired people. This is what defines the outcomes in the classroom and other situations in day to day life. I think the whole series of lectures is great, not only for fellow-researchers but also for parents, teachers and educational audiologists. It is important that these individuals collaborate as a group, understand each other and are on the level with the latest developments in research.”
The ARC 2014 conference "Hearing Aids and the Brain" takes place on Wednesday, march 26, 8:00 AM - 5:30 PM (room 330D).
Leendert van der Ent