Dr Will Sedley provides his opinions on how to objectively ‘measure’ tinnitus – the first crucial step in developing effective treatments or even a cure – as an example of the kind of project that Action on Hearing Loss is funding
I studied medicine at the University of Nottingham and, after graduating in 2007, took up a series of positions in Newcastle and nearby hospitals. I’m fascinated by how the brain works, and why we see, hear and feel the things we do. When I came across tinnitus, I realised that this captured every fascinating aspect of perception – and, most importantly, presented a massive unsolved problem in modern medicine.
I completed my PhD into brain mechanisms for tinnitus in 2015. I currently work as a specialist registrar in neurology, and as a postdoctoral research scientist, in Newcastle University’s Institute of Neuroscience.
The search for treatment
At the time of my PhD, there were two competing schools of thought about tinnitus. All we really knew for certain was that it’s usually caused, in some way, by hearing loss.
One view was that the hearing loss causes the brain to ‘turn up the volume’ to compensate and that this inadvertently turns up the volume on spontaneous, random brain cell firing. In other words, the tinnitus sound that people hear.
The other view likened tinnitus to ‘phantom limb’ pain – the lack of hearing input in the higher frequency ranges means that the brain has to fill in the missing input from somewhere. Our brains are constantly weighing up what our senses are telling us against our predictions of what we expect to hear.
So it was thought that these predictive mechanisms were going into overdrive and making up the missing input from the brain’s memories of sound, or from sound inputs in undamaged frequency ranges.
The two accounts seemed mutually exclusive and also there were a lot of paradoxes that neither could explain. I developed a framework which incorporates aspects of both but with the fundamental difference that the brain is not using predictive mechanisms to make up the tinnitus sound.
Instead, it’s usually successful in using predictions of silence to overrule the tinnitus signal – and tinnitus occurs when these mechanisms fail to fully override it. This opens up a number of testable hypotheses about how tinnitus is caused. It might even help in the search for treatment if we can find ways to modify the relevant predictive mechanisms.
Tackling the issue of trying to come up with a convenient, accurate and objective test for tinnitus is an example of a new project, funded by Action on Hearing Loss. The lack of such a ‘biomarker’ has been a massive barrier to tinnitus research up to now. The method of examining a type of electrical brain response to sounds started out as an attempt to test my theory of how predictive mechanisms may cause, or suppress, tinnitus.
A range of different sounds are played to a volunteer, and the pattern of these responses across different conditions (such as sounds that are louder than expected versus others that are quieter than expected) can reveal whether the brain’s predictions of sounds are being skewed in a particular direction.
I’ve seen a very different pattern of results in people with tinnitus compared to people without it. The brain recordings can be used to categorise people as having tinnitus or not with fairly high accuracy. Importantly, this method is also quick, cheap, and requires no training, so it has the potential to transform the way tinnitus research is conducted internationally.
From the volunteers’ point of view, it’s really simple; they wear an electrode cap and headphones and we play some beeps to them, which they ignore while watching a subtitled film. The work so far is almost ready for scientific publication and now, with this new funding, the next stage will be to improve the accuracy and efficiency of the method (as well as learning more about the brain mechanisms of tinnitus). While it’s not in itself a treatment, an accurate and quick test for tinnitus is essential for developing effective treatments for the condition in future. If it lives up to expectation, it will be a major step towards treatment or even a cure.
Human studies of tinnitus are vital if we’re to understand it better, and for developing effective treatments. We rely heavily on the goodwill of lots of people with tinnitus who give generously of their time. Happily, almost every one of my volunteers has found the experience interesting. Often, they feel that tinnitus isn’t taken all that seriously by health practitioners, so they appreciate the experience of meeting people who are deeply interested in it.
Tinnitus can seem a very unattractive condition to study, either because the symptom can sound rather boring, or because it’s not really seen as a big problem compared to, say, cancer or dementia.
In reality, to truly understand tinnitus, you need to understand perception – which means getting to grips with a range of some of the most fascinating aspects of neuroscience, including the unsolved problems remaining. In terms of the importance of the condition, 1% of the UK population are suffering for years (or even decades), because of it. They may not talk about it much – or even at all – but we probably all know people who struggle with tinnitus.
Early on in my career, things were rather all-or-nothing. I would work on one research project at a time and commit everything to it. When things went well, it was incredibly rewarding, and when experiments or whole studies failed, it would feel like the bottom had fallen out of my world.
Now I have so many things going on at once (research, clinical work, family) that there’s just not enough hours in the day. But it’s great because I enjoy every aspect of what I do in life.
Research is one of the most rewarding long-term ‘hobbies’ to have. The feeling of being able to apply your own creativity to tackle important challenges and fascinating puzzles is wonderful. The downside is that the research progresses much more slowly than I’d like.
No telling when
I don’t want to fall into the trap of saying we’re on the cusp of curing tinnitus or speculating about when we will cure it. I think it can, and will, be cured eventually – but there’s really no telling when, or how.
Ideally, my ultimate goal would be to conclusively work out how tinnitus occurs (including, along the way, how perception in general works), and develop a cure or a safe, non-invasive and effective treatment – perhaps one that can be freely downloaded as a smartphone app. Realistically, I’d be pleased to move the field of research in any direction that eventually benefits people struggling with tinnitus.
Dr Will Sedley
Action on Hearing Loss
Tel: +44 (0)808 808 0123