Why Has Audiology Taken a Back Seat in Misophonia Research?

As misophonia research has grown over the past 10 years, the disorder has been studied in the fields of audiology, neuroscience, psychology, psychiatry, and more. This is wonderful news. Yet, how do we integrate findings across these disparate branches of knowledge, especially since each area of study contains different terminology? Psychology and audiology use vastly different language. Psychology (and mental health) terms are more accessible because they are used in everyday language. Most people know what anxiety is, for example. Audiology terms, on the other hand, are more esoteric. Neuroscience and psychology are also distinct fields, with distinct languages, but they're like long-time colleagues who are used to working together. They are familiar with one another, and researchers in each field know how to find common ground.

Audiology and mental health, however, are less intertwined, leaving some important lapses in both research and treatment for misophonia. When we speak of “auditory,” this includes what happens in the ear as well as what happens to sound in the brain. What is audiology’s contribution to the understanding of misophonia? What do we know? What needs to be studied? To fill in some of these blanks, I spoke with Dr. Julia Campbell, audiologist, professor, and researcher at The University of Texas at Austin.

Jennifer Brout: Dr. Campbell, would you briefly explain how sound travels from the outside world and through the ear, and is then perceived by the brain?

Julia Campbell: Sound waves enter the outer ear through the canal. In response, the eardrum vibrates. Vibrations are picked up by tiny bones in the middle ear, which are called ossicles, which amplify these waves and transmit them to the inner ear, specifically the cochlea [a snail-like structure filled with fluid and tiny hairs]. From the cochlea, electric signals travel to higher parts of the brain where meaning is attached to sound. Sound, like all the sensory information, only finds meaning as it moves through the perceptual process of the brain.

JB: So, the peripheral parts of the auditory system (outer ear—auditory nerve) transmit signals to the central auditory system, which includes the brain stem and the brain.

JC: Yes.

JB: Where in this process are we looking for misophonia?

JC: We have been looking in the central nervous system, mainly in the cortex, which again is where auditory information is interpreted and integrated with other brain areas. Most studies have focused on higher levels of the brain related to cognition, executive functioning, and emotions. However, there has been very little research on all levels of the auditory system, starting at the cochlea, moving through the brainstem, and up through the primary auditory cortex. So far, findings do not indicate any inner ear or auditory brainstem anomalies related to misophonia, but there are some new studies that suggest possible atypicality at the level of the thalamus [a structure deep in the brain that serves as a relay center for sensory and motor signals, regulating consciousness, sleep, and alertness] and auditory cortex.

JB: Why is this important?

JC: It is important to know if atypicality in the ear or brainstem structures may be impacting the perception of sound at higher levels of the auditory central nervous system. For instance, it could be that a deficit in the inner ear or brainstem causes downstream processing issues related to or resulting in misophonia. Therefore, the cause of the perceptual problem (located in the cortex) is occurring at a lower level, which would affect the intervention approach. This possibility should at least be ruled out before assuming the issue is only occurring in the cortex.

JB: You’ve said that you think there may be multiple causes of misophonia.

JC: Yes. Misophonia may result from various causes, but we really don’t know. How do we pinpoint a single cause when the brain is so complicated, and perception involves interaction between basic sensory processing (including visual processing), cognition, and emotions? Because of this, it is possible that we may end up with subtypes of misophonia related to etiology. One thing we do know is that the onset of misophonia typically occurs in childhood. This points to a possible role of developmental processes that may give rise to these symptoms.

JB: I am glad you mentioned visual processing because we know this is also an issue for people with misophonia, thus the term misokinesia. We always want to find “the answer,” but it is much more complicated. All the senses work together, so the idea that visual stimuli are also triggering does not mean we should stop looking at auditory processing, right?

JC: Right.

JB: Switching up the topic a bit…do you think auditory gating [the brain's ability to suppress responses to repetitive acoustic stimuli] may have anything to do with misophonia?

JC: Gating is a very interesting issue. Auditory gating happens at many different levels of the brain. I look at pre-attentive gating—how the brain modulates incoming stimuli at the nonconscious level—so, again, lower levels of the brain. If auditory gating is impaired, then the higher executive centers are flooded with too much information.

JB: Is this like filtering in central auditory processing disorder (CAPD)?

JC: Yes, it is possible that this function is important in CAPD. For instance, a hallmark characteristic of CAPD is that individuals cannot separate speech from background noise, and the result is impairment in the understanding of language, because higher levels of the brain may become overwhelmed with too much auditory information, compromising cognition.

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JB: This leads me right to my next question. Wouldn’t it help us understand misophonia if we knew if there was co-occurrence with CAPD? Wouldn’t this be easy to do?

JC: Yes, and yes. It would be easy for audiologists to give a misophonia screener to their CAPD patients—at least we would get an idea about the prevalence of the comorbidity of these disorders that could be followed up with more rigorous study.

JB: There is so much more we could talk about but my final question is—what study would you like to see next for misophonia?

JC: I would like to see more studies that include auditory EEG measures from the inner ear, through the brainstem, and up through the cortex so that we would have more specific information about the auditory pathway. MRI studies are great, again for the higher brain centers, but we really need to get a more comprehensive picture of the entire pathway.

There was a lot more that I could have discussed with Dr. Campbell. Most importantly, I realize that although audiology is so central to misophonia, the research has remained on the periphery. As an individual with misophonia, I would certainly like to see this change.