Text for video abstract of 'Tinnitus: at a crossroad between phantom perception and sleep'
Hello, welcome to this video abstract of the review article titled ‘Tinnitus: at a crossroad between phantom perception and sleep’ published in Brain Communications. My name is Linus Milinski, and I am first author of the article. In this work we bring together recent developments in the fields of tinnitus and sleep research and, in conclusion, propose a new perspective on the interaction between auditory phantom percepts and natural brain state dynamics.
Subjective tinnitus is the perception of a constant phantom sound generated by the brain. Often this comes in form of a persistent ringing or hissing percept. To give you an impression, here is a brief audio clip of what tinnitus can sound like. Please be aware that the audio clip may be unpleasant or triggering for people who have tinnitus. [tinnitus sample is played] Tinnitus affects about 15% of the world population and can be a debilitating condition that is associated with sleep problems depression, and anxiety.
While the cause of tinnitus is not always known in individual cases, the most common triggers are considered to be intense noise exposure such as in a live concert or any form of hearing loss.
Most often, tinnitus is associated with some form of hyperexcitability or spontaneous hyperactivity in multiple brain regions. And while the auditory system is often strongly involved in producing this aberrant activity, we know now that actually many brain areas show altered activity in tinnitus. This image on the left shows only a subset of regions affected. It has been suggested that it is this global representation of tinnitus in the brain that makes it such a salient percept and debilitating condition.
[Slide 4 (panel titled ‘Sleep’ appears)]
However, there is another situation where the brain shows rather widespread alteration of spontaneous activity. And this is during sleep. In particular during NREM sleep, the state we spend most time in while we are sleeping, the brain produces this very stereotypical, slow, oscillating activity, that spreads across the cortex. Importantly, this slow-wave activity is present across many regions involved in tinnitus. This spatial overlap between tinnitus activity and sleep oscillatory activity has important implications.
[Slide 5 (brain cartoon on the right changes)]
First, it could explain why interrupted sleep is such a common symptom in tinnitus patients. While a normal brain is able to express widespread sleep-like activity, a tinnitus brain might show these persistent hotspots of aberrant activity. The intense interconnectivity of the cortex could then lead to a widespread effect of this hot spot on brain wide activity and also to an interference with sleep in a substantial manner.
[Slide 6 (brain cartoon displays ‘Zzzz…’)]
On the other hand, if the sleep drive is very high, for example after a period of extended wakefulness, there is evidence to suggest that aberrant activity could be, to a degree, suppressed.
In other words, it is possible that there is a dynamic interaction between the expression of NREM slow-wave activity and tinnitus-related activity in the brain. Specifically, tinnitus activity might be reduced during intense NREM sleep. But as sleep pressure decreases and with it the drive of the brain to express slow-wave activity, aberrant brain activity could regain its potential to affect the brain on a wide scale as observed during wakefulness in tinnitus patients.
In this review, we describe the mechanisms underlying such a putative interaction between sleep and tinnitus-related activity, based on brain activity on the level of single neurons up to that of the whole brain.
Finally, the spatial overlap between brain regions where activity is modulated by sleep and by tinnitus might have an additional implication. It is now widely appreciated that the formation of persistent tinnitus requires plasticity in central brain regions. And some of the plasticity processes thought to be underlying tinnitus formation are known to be consolidated during sleep. In this review we are describing how sleep could be connected to long-term tinnitus formation and development.
We hope that this new perspective on sleep and tinnitus will stimulate discussions on harnessing natural variations in brain state to understand phantom percepts generated by equally spontaneous activities. We describe how bringing together sleep and tinnitus research could lead to a new target for understanding tinnitus and for developing treatments based on known methods of sleep manipulation. With that, I want to thank my Co-authors and the funding bodies that supported this work, in particular the royal national institute for deaf people. Thank you for your attention and for your interest in our work.