I lost all my hearing after contracting meningitis when I was 19 months old. When I was three, I was lucky enough to be one of the first 50 children in the UK to receive a unilateral cochlear implant. By the time I was eight, I could speak fluently and had caught up with my hearing peers. That was when I decided that, when I was older, I wanted to be able to study at the best universities, so that I could do my bit for cochlear implant research one day.
I graduated from Oxford University with a First Class Honours degree in Physiology and Psychology, and also an MSc in Neuroscience. Now, thanks to funding from Action on Hearing Loss and Cochlear Ltd, I’ve just successfully completed my PhD at UCL (University College London). I’ve been working with Professor Stuart Rosen and Dr Tim Green to research the best way to develop an accurate tool to assess listening effort.
A common (often underestimated) problem for people with hearing loss – even when it’s mild – is that listening can be hard work. This is because their listening effort has increased. Listening effort is a natural consequence of hearing, and is the amount of brain processing required to pick out what we want to hear from the noisy world of sound. If listening becomes difficult, then listening effort increases.
This problem applies to cochlear implant users, too. However, this fact often takes people by surprise, because they may have gained the impression that, as soon as the implant is well established, the patient has few major listening problems. This is not actually true. Although cochlear implant users’ audiograms can become very similar to that seen in someone with only minimal hearing loss, the cochlear implant produces an artificial sound that’s different to what’s normally heard. This can increase their listening effort.
Clinical assessments following an implant mainly focus on speech understanding (particularly when noise is present in the background), with no actual measurement of the listening effort required for that individual.
This lack of objective measurement of listening effort is worrying because, although the cochlear implant is fantastic technology, it is not a cure for deafness. So, there are still gaps in the sound information provided by the cochlear implant, which the brain has to compensate for. As a result, the brain is having to put in ‘overtime’ to ensure that the cochlear implant user can understand what they’re hearing. This creates a greater ‘cognitive load’ for the brain. Now, the brain can cope with the missing information very well (which is why we have all the success stories), but this extra cognitive load can become a burden. This is especially true if the cognitive load is greater than usual for a sustained period of time.
What’s particularly concerning is that this extra cognitive load (caused by increased listening effort) can increase the risk of debilitating, long-term health consequences, both physical and mental, including tiredness (even to the point of exhaustion) and depression. This is because the brain is more likely to become so overloaded with the extra processing that it ends up beingoverwhelmed.
It’s important to understand that cochlear implant users, even when they’re performing well (in terms of speech perception), may still be experiencing stress because of the extra listening effort involved. This is why a clinical test should be developed, so that we can keep a careful eye on listening effort levels.
As part of my research, I used a behavioural test where the participant had to multi-task by simultaneously listening to spoken sentences (with or without noise in the background) and counting numbers (which flashed up on a computer screen). By asking the participant to multi-task, you can measure how the brain is managing the cognitive load. From this, you can calculate the listening effort.
The results suggest that cochlear implant users are, indeed, experiencing extra listening effort compared to normal hearing controls. Not only this, but the cochlear implant users’ listening effort is significantly higher even when the listening conditions are as good as they can be (such as a quiet room with no background noise whatsoever).
It was previously assumed that implant users only really experience difficulty in noisy situations. But this may only be part of the story: it seems possible, from my results, that their brains are working harder from the moment they switch on the implant, even when there is no noise present at all.
Cochlear implant users should not only hear well, they should also hear healthily. Listening effort needs to be monitored, by clinicians and also by the cochlear implant users themselves. Schools and workplaces, too, need to be more aware of the extra burden a cochlear implant user is having to cope with. They also need to support the cochlear implant users in finding ways to control their listening effort levels. Every cochlear implant user is unique in how they process sound, how they’re affected by listening effort, and also how they cope with listening effort.
Potential ways to keep listening effort manageable could include taking more breaks (during a meeting, for instance), having short periods of quiet during the day, or finding time each day to carry out an activity which is relaxing (such as ‘mindfulness’ exercises, ‘mindful’ colouring, or a craft such as knitting). Essentially, the brain just needs the opportunity each day to relax, recover and generally de-stress.
I owe a debt to the incredible, life-changing cochlear implant technology. I wouldn’t be where I am today, with the opportunities I’ve had and my academic achievements, without it. I believe my debt is best repaid (at least, in part) by finding ways of further improving the outcomes for other cochlear implant users. I hope that, with my personal experience of living with the implant, I’ll be able to use my additional insight and understanding to make a positive contribution. Ultimately, I want to help other cochlear implant users gain maximum benefit from the technology so that they can fulfil their own true potential.
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