“Psychoacoustics of Tinnitus: Lost in Translation,” Acoustics Today, 17(1), 35-42. https://acousticstoday.org/psychoacoustics-of-tinnitus-lost-in-translation-christopher-spankovich/
Authors: Christopher Spankovich, Sarah Faucette, Celia Escabi, and Edward Lobarinas
Published: Spring 2021
In this episode, we speak with Christopher Spankovich of the University of Mississippi Medical Center about his article, “Psychoacoustics of Tinnitus: Lost in Translation,” which appeared in the Spring 2021 issue of Acoustics Today. In this interview, we discuss what tinnitus is, how it is (or isn't) measured, treatments for the disorder, and current research in animals and humans.
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Kat Setzer (KS)
Welcome to Across Acoustics, the official podcast of the Acoustical Society of America’s Publications office. On this podcast, we will highlight research from our four publications, The Journal of the Acoustical Society of America, also known as JASA, JASA Express Letters, Proceedings of Meetings on Acoustics, also known as POMA, and Acoustics Today. I'm your host, Kat Setzer, Editorial Associate for the ASA.
Joining me today is Christopher Spankovich of the University of Mississippi Medical Center. We'll be discussing his article, “Psychoacoustics of Tinnitus: Lost in Translation,” which appeared in the spring 2021 issue of Acoustics Today. Thanks for taking the time to speak with us today. Chris, how are you?
Christopher Spankovich (CS)
Good. Happy to be here.
First, tell us a bit about yourself.
Sure, my name is Chris Spankovich. I am the vice chair of research for the Department of Otolaryngology and Head and Neck Surgery at the University of Mississippi Medical Center in Jackson, Mississippi. And I'm also a clinical audiologist that sees patients every week, specifically devoted to patients with complaints of tinnitus and sound sensitivity.
Awesome. Very cool. So what is tinnitus?
That's a good question. So a better question would be, “What is not tinnitus?” So tinnitus is the perception of ringing, buzzing, humming, that does not have an external source. Now, that being said, probably a given number of individuals in the audience have experienced a brief perception of ringing or buzzing/humming that lasts a few seconds and goes away. And that might happen randomly a few times a year. That is not truly tinnitus. Rather, we refer to that as a transient ear noise or sometimes a phrase, “spontaneous tinnitus,” is used. However, for it to be considered tinnitus, a clinical type of tinnitus, we get more of a definition of experiencing ringing/buzzing/humming at least five minutes one time in the past year. So it has to have that five minutes of duration to be considered a true tinnitus. Now, that being said, as well, the vast majority of patients that come to see us are experiencing tinnitus more often than one time for five minutes in the past year. The vast majority of individuals with tinnitus that have bothersome tinnitus or that pursued some type of intervention are the individuals with more chronic forms of tinnitus that have a more consistent pattern where they experienced it at least monthly, daily, weekly, or even constantly.
Oh, yeah, that seems pretty intrusive. What causes tinnitus?
So the most common cause of tinnitus is going to be reduced input into the auditory pathway. So though our ears are mechanism of getting sound to be able to hear, really we hear with our brain, and so our ears sort of serve as transformers taking an acoustic form of energy and converting it to the language the brain speaks, which is electrochemical. So when there's the disruption in that input, that now the brain is not getting its normal type of ambient sound and the sound that it used to get, the brain changes. It tries to compensate for that lack of peripheral input. And that is what in turn creates the changes that underlie the perception of tinnitus. Now, a person can experience transient tinnitus if we place them in a sound-treated room, or with this audience, an anechoic sound chamber. If you put an individual in that room and leave them in there for five minutes, the vast majority of individuals, even if they've never had tinnitus before or have completely normal hearing, will experience likely a tinnitus-like perception in that environment. Now, that doesn't mean we caused permanent damage to their auditory pathway or created chronic central changes that are going to create a sustained perception of tinnitus, but they will experience tinnitus in that very quiet environment because we disrupted normal input to the brain. We put them into an artificial environment, and their brain is trying to hear over that silent environment, in a quiet environment. Once they've come out of that sound-treated room or come out of that anechoic sound chamber, they're no longer experiencing tinnitus.
And that's different than someone that has some type of chronic change to the status of their hearing system. So a person that has noise-induced hearing loss or has age-related hearing loss has some type of damage to the peripheral auditory pathway that's now going to result in chronic sustained central changes that are going to underlie this more chronic version of tinnitus.
Okay, I see. So in your article, you mention that there's a critical difference between the perception of tinnitus versus the reaction to it. Can you explain?
Yes, so here, where we're using the term “perception,” really, we're referring to the awareness that there is tinnitus there now, and it was not there previously. And at some level, the interpretation of that tinnitus. When an individual develops ringing/buzzing in their ears, their first reaction is unlikely, “Oh, this is good. This means that I'm going to live longer,” or, “Did I just develop superhearing?” You hear ringing/buzzing in your ears, your first reaction is, “Well, I didn't have this previously. This is not my normal. This is a sign that something is off or something is wrong.” And that makes sense. So that's our really the perception of our tinnitus. Ultimately, how the brain categorizes that tinnitus as being something negative, then can lead to the reaction to the tinnitus, which is the tinnitus becomes something that the brain begins to attend to it can't really figure out where it's coming from, because it doesn't have an external source. This begins to increase some stress within the individual, which increases the attention, which increases the loudness of the tinnitus, which increases the volatile nature of the tinnitus. That can lead to behavioral changes that are negative in how they manifest, further sort of creating this vicious cycle that the tinnitus is something bad and not good, and that it is having a significant impact on that person's quality of life.
Okay, so you're like concerned with the psychological impact from the tinnitus, essentially?
Correct. So that's also part of the perception as well, though, you know. You're perceiving something, but ultimately, the reaction is the more significant issue. If a person just has tinnitus, but they aren't bothered by it, then it's not as big of a deal, versus someone that has it, and they are extremely bothered by it.
Right. Right, that makes sense. So that leads into our next question, is there a cure for tinnitus?
So, for most forms of tinnitus, no. You know, when we're talking about tinnitus, there's more than one type of tinnitus. The most common type of tinnitus individuals experience we call “primary tinnitus,” and that's usually experienced as the ringing/buzzing/humming/eeeeee type of sound. And that is usually due to, again, some type of damage at the level of the peripheral auditory pathway: noise-induced hearing loss, drug-induced hearing loss, something to that effect. There's other forms of tinnitus as well. For example, secondary tinnitus, where a person hears their heartbeat in their ear, and that might be related to hypertension or something. So we get their hypertension under control, you can resolve the pulsetile tinnitus perception that person has. Some forms of primary tinnitus, for example, if tinnitus is due to the person's ears being occluded with wax, and now ear wax has created enough of a change in their hearing sensitivity like putting their ears in a sound-treated room briefly. Well. Now they’re experiencing tinnitus while their ears are occluded with that wax. But once the wax is removed, they no longer perceive the tinnitus because their system’s flooded again, with the natural ambient sound that it expects.
However, those aren’t the more common forms of tinnitus, right? We're talking more about chronic volatile tinnitus, and when we're talking about chronic forms of tinnitus. Unfortunately, no, there is no cure for that; there's no surgery, there's no drug that we’ve been able to identify that can consistently turn off the perception of tinnitus in any type of sustained way. That being said, there are management tools to help an individual with tinnitus, and that often involves some level of counseling on what tinnitus is, what it's not, and applications of sound to help modulate the perception of tge tinnitus. Ultimately, the two things that hopefully helping the individual manage their tinnitus is learning ways to reduce their attention to the tinnitus and using sound to help reduce that perception as well, to ultimately lead to habituation, where the brain may notice this once in a while, but is otherwise able to put it to the backburner.
Okay, so it's not really a cure, but you're helping people learn to cope and thus have a solution for the problem.
So currently, there isn't a widely accepted method of identifying or quantifying primary tinnitus. Does there need to be one? What are the options for measuring tinnitus?
So that's depending on what you are attempting to quantify. Going back to what we were just mentioning about perception versus reaction—we can indeed quantify the reactions to tinnitus. There are there are numerous validated scales, such as the tinnitus functional index, the tinnitus handicap inventory, that can help clinicians quantify how tinnitus is impacting a person's function and their quality of life. We can also quantify the qualities of the tinnitus perception, such as performing pitch match, and loudness match. Of course, this is dependent on the subjective feedback of the patient.
What we do not have is the ability through some type of imaging or electrophysiological measure to provide an objective measure of tinnitus. Now, that being said, we do have objective measures of cochlear and auditory neural function such as otoacoustic emissions, auditory evoked potentials, that can objectively show evidence of auditory pathology that underlies the eventual tinnitus perception and that we can correspond to the personal tinnitus perception. But currently, we do not have the capability of objectively going in and showing, “Oh, here is the tinnitus. This is where it's happening in the brainstem of brain and this is the source of that signal.
Okay, I see. So in your article, you mentioned that animals can experience tinnitus. How do researchers measure tinnitus in animals?
So, my colleague and one of the co-authors on the article, Edward Lobarinas, would say that you have to learn to speak rat. Just kidding. But in reality, we use very common approaches in animal behavioral studies—operant-conditioning strategies, reflex-based strategies-- to try to determine the likely presence of tinnitus or not. If you have tinnitus, if you have a perception of ringing/buzzing in your ears, then your noise floor has changed, your experience of quiet has changed. Now, there's no such thing as the absence of sound in the real world, or even in an anechoic sound chamber, because a person's making sound. So there's no such thing as silence, truly. But when you have tinnitus, now what you perceived as quiet has now changed because you have this new perception of this constant, ringing/roaring type of sound in your ears.
So what we can do is use animal models to determine if they are, if what their perception of quiet has changed to now involve a sound. So you can train an animal, for example, to drink or not to drink when they hear a sound. And you can then give the animal tinnitus and once the animal has tinnitus, and they're placed in the testing environment, they stop licking because now they have this constant perception of sound in the environment. Or we can use more of a reflex-based strategy, a common one has been using a startle reflex. So this is gap prepulse inhibition to a startle—a startle that's created by an acoustic signal or a startle created by air puff to the back of the animal's neck. So, for example, if someone snuck up behind you and yelled, that would cause you to startle, right?
But if I told you right before that person came up behind you, “Hey, that guy's gonna come up behind you and yell,” you’d start a little bit, but it would be less because I just told you about it. So we can use that to our advantage in animal models where we can have a startle signal. We play the startle signal states allows them and we measure how much the animal startles. And that can be using some type of piezoelectric transducer in terms of how much the animal presses on it. And then we could put a little gap right before, a little gap silent gap in the background noise, right before that startle sound comes at the person, the animal detects the gap, then that can now attenuate the amount of startle response just like you would experience if I told you someone was coming behind the door to scream. If the animal has tinnitus, the idea is that they can't detect that gap as well, because that silent gap is being filled by the tinnitus, and so their startle is not suppressed.
Okay, I see. So I guess the follow up question then is how do findings related to animal tinnitus translate to human tinnitus?
Well, you know, you can gain a great deal of insight on environmental and genetic implications for auditory pathology from animal models. Animal models have been very critical to our understanding of the auditory and the vestibular system. And indeed, we can induce tinnitus in animal models that show reliable evidence that an animal is perceiving a sound. However, there are inherent limitations. One is sort of a mixed bag of, you know, is that what we're using to induce tinnitus, is that also creating hearing loss? Is that also creating sound sensitivity or hyperacusis? How do you differentiate those things in that model? Is it the hearing loss creating temporal issues that is more affecting the gap detection, rather than the tinnitus filling that sound? Yeah. And there are inherent limitations, specifically for the most problematic element for humans, which is the affective reaction, the emotional component, and the affective reaction that the individual has to the tinnitus. That is the element that we are not able to succinctly or consistently or reliably demonstrate through some type of animal.
Right, that makes sense. So you discuss this paradigm that suggests the presence of tinnitus disrupts the ability of the animal to detect the silent gap, and as a result, the startle response is less suppressed. How does this translate to humans?
So the translation to humans is less consistent. You know, in the animal model, really, we're using a reflexive behavior like a startle response, some of the studies that have looked at this in humans have initially tried to look at perceptual effects. So can a human perceive a silent gap before noise, even if that silent gap or the noisy background is pitch matched to their tinnitus perception where it would make it more difficult? And the answer is yes, they can still detect the silent gap. Because we have a brain and we're pretty good at, you know, separating sound sources and doing all those things. Now, that being said, that's not really what's happening in the animal, the animal models look is looking at a reflexive behavior. So there is other work looking at reflex behaviors like an eye blink, or something like that, to a startle signal, or some other type of reflexive behavior and trying to see if that influences the model at all. And there's some evidence to support that it does, but again, it's not exactly clear. So the translation between sort of some of these animal-based models to the human condition, some of that is lost in translation, and more than likely what there needs to be as a combination of different approaches—perhaps some type of psychophysical component, along with an imaging and electrophysiological component combined, to sort of better isolate and show objective evidence.
Ah, I see. So, a multifaceted approach is obviously more helpful than just using animal models.
So, what challenges do psychoacousticians continue to face with regards to the study of tinnitus?
So, one, how can we merge objective measures of auditory function, such as auditory evoked potentials or some type of imaging, along with psychophysical approaches to try to enhance our ability to differentiate true tinnitus from someone that was, for example, trying to malinger or fake having a tinnitus reaction? How can we objectively demonstrate that they truly are experiencing tinnitus beyond them reporting it? And so again, I think that's going to have to be a merger of a combination of these different approaches, not just like a physical, but also imaging as well as some type of electrophysiological response, coming together to really be able to isolate and demonstrate that. Two, how can we more realistically represent the human condition in animal models? Again, a major component of the human condition is not necessarily the perception of tinnitus, because we can take anyone, put them in the sound-treated room or anechoic chamber, and most of them will experience tinnitus. That doesn't mean they have bothersome chronic tinnitus. And, really, the vast majority of people out there that have chronic tinnitus, even, that have constant tinnitus from whatever age-related changes or noise exposure, aren't very bothered by it. So for those individuals, you know, it is not this huge, significant issue. but for a segment of the population, yes, it is something that really, really is impacting their quality of life in a significant way. And that has to do with the affective reaction to the tinnitus and not the tinnitus itself. And that affective component is not something we capture as well in animal models, and an area that needs to be enhanced as well, so that we can better target that for some type of management approaches.
Gotcha. So, finally, for individuals with tinnitus, who are listening to this podcast, do you have any parting comments?
Yes. First of all, there is hope. You do not have to just learn to live with your tinnitus. There are ways to help with tinnitus. There are management approaches that are very effective and very helpful. Now, will they necessarily cure your tinnitus and take the signal out of your brain? No. But will they help to get you a place where it is less noticeable and less impactful on your quality of life? Yes. So my recommendation is to reach out to find an audiologist in your area. Commonly audiologists are individuals that provide evaluation and management services of individuals with tinnitus and hearing losses, again, the most common cause of tinnitus. Reach out and find an audiologist in your area that provides tinnitus evaluation and management services, and talk with them. And I think you'll find that there are things to help in that you don’t just have to sit there and just constantly deal with this.
That's a comforting message to end our discussion on. Well, thank you for giving us insight into this common hearing disorder. It's been great talking to you, and I hope our listeners appreciate it.
No problem. Thank you for having me.
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