Misophonia Breakthrough Study: An interview with Sukhbinder Kumar

 Jennifer Jo Brout, PsyD and Michael Mannino, PhD candidate

Dr. Sukhbinder Kumar, and his team from the Institute of Neuroscience at Newcastle University and the Wellcome Centre for NeuroImaging at University College London (UCL) published a groundbreaking misophonia study, which recently appeared in Current Biology.

What makes this study “ground-breaking?”

In an interview with Dr. Kumar, he explains the study and what it might mean for people with misophonia.Dr. Kumar states that his team’s findings provide "strong evidence that misophonia is a “real disorder.  Specifically, using Magnetic resonance imaging (MRI) Kumar’s team found identifiable differences in the brains of misophonic individuals. The study reveals numerous important findings.

Courtesy of Pexels
Source: Courtesy of Pexels

First, there is a notable difference in the connectivity in the frontal lobe between the cerebral hemispheres in people with misophonia. The difference appears to be due to higher myelination in the ventromedial prefrontal cortex (vmPFC). The vmPFC sits almost right above the eye-socket, the bottom middle towards the front of the brain. It is involved in processing and regulation of emotions like fear and empathy, and decision making

"The higher myelination in this area of the brain in misophonia subjects suggests abnormal connectivity"

The myelin sheath cells are surround the connecting axons of neurons, allowing for, and increasing electrical conductivity between brain cells. Without this, cells could not communicate properly.

Also, the ventromedial prefrontal cortex is central to understanding misophonia because it is part of a complicated network of connections between numerous other areas of the brain. It both receives sensory information, processes that information and influences the functioning of many other brain areas including those involved in memory, olfaction and perhaps of great importance, the amygdala (where fight/flight is mediated and where salience, or importance, is assigned to incoming sensory stimuli).

Dr. Lorenzo Díaz-Mataix (LeDoux Lab, NYU) comments: "In the study we are conducting, we explore individual different responses in rodents induced by acoustic stimuli, [which they associate with threat]. The auditory threat then triggers neural activity in the amygdala  behavioral responses (freezing), autonomic activity (increases in heart rate, blood pressure) and the release of stress hormones. These neural, behavioral, autonomic, and endocrine responses vary across individuals, with some rats consistently responding strongly and others weakly to the same stimulus. This work relates to the Kumar study since the Insula connects directly with the Amygdala. We believe that our experiments under controlled laboratory conditions will complement and will add to our understanding of brain circuits that underlie symptoms related to threat processing in psychiatric conditions, including misophonia."

The study also revealed that a major area involved in the brain’s ability to pick out what it thinks are “salient” ,or important, stimuli (the anterior insular cortex, or AIC) showed greater activation for misophonia subjects responding to trigger sounds.  The AIC  is involved in processing emotions and integrating sensory stimuli (such as sounds) from the both the outside world and from within the body. 

Here, “salient” means picking out or paying attention to something that stands out from its neighbors, like off-color in the case of vision, or in this case, an off sound. Importantly, this area also showed abnormal “functional” connectivity to other brain regions highly involved in processing emotions, including the amygdala, the vmPFC, and the posteromedial cortex (PMC), also involved in emotional regulation. 

Dr. Kumar hypothesizes that the difficulty in processing sensory information in these brain networks leads to a “mismatch between how a person perceives their physical state and what their physical state really is". This refers to an often overlooked sense “interoception”, which allows us to accurately perceive our body states. As an example, Dr. Kumar explained, “that a person may feel as though they have a dry mouth. Yet objectively there mouth is not dry”. Dr. Kumar is very interested in this finding and is continuing research on how this relates to misophonia.

The take home message here is that due to this aberrant connectivity those with misophonia misinterpret the common misophonic trigger sounds in a way that causes their bodies to respond as though they are under threat.  The amygdala is the part of all this that takes all this “mis”information, and then tells the body,  ‘lets do something about this'.

Dr. Kumar hopes that this study will help lead to treatment. Treatment possibilities include learning ways to self- regulate (or bring down the nervous system arousal). We also spoke about the potential of memory re-consolidation therapy. Memory reconsolidation therapy would involve changing the physiological response to the trigger sound. This was developed in the Joseph LeDoux lab at NYU and has been successfully trialed in rodents, and is currently being trialed successfully in human beings for Post Traumatic Stress Disorder and for phobias.

Dr. Joseph LeDoux comments: This seems like an important and well-conducted study by research team from a leading functional imaging center published in a top-tier journal implicating the insula cortex in auditory responsivity in misophonia. As the study shows, notes the insula is well situated to play a role processing sounds as threats given that it receives auditory inputs and is also connected with the amygdala and medial cortical areas.  I was surprised that the anterior insula was found to be acoustically responsive in this study since most the posterior insula is usually found to be the sensory (including auditory) responsive region. Regardless, this seems to be an important advance in linking symptoms in misophonia to the brain. 

Dr. Kumar adds that this study validates misophonia is it’s own disorder. It cannot be classified within any psychiatric or specific neurological disorder. When asked if he thought misophonia should be classified as neurological or psychiatric, Dr. Kumar explained that the lines between psychiatric and neurological are blurred. “Many psychiatric disorders are neurologically driven”, and this differentiation may be irrelevant."

For more information on Dr. Kumar and related studies http://ttp://misophonia-research.com/misophonia-advisory-board/

For more information on misophonia https://www.misophoniainternational.com/what-is-misophonia/

References

Kumar, S., Hancock, OT., Sedley,, W., Winston, JS., Callaghan, MF., Allen M., Cope, TE., Gander, PE., Bamiou, DE., Griffiths, TD (2017). The brain basis for misophonia. Current Biology (in Press).DOI: 10.1016/j.cub.2016.12.048

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