Misophonia: Role of mirroring

Misophonia is a condition where people have extreme distress towards everyday bodily sounds like eating, chewing, breathing etc which are called trigger sounds. This causes the sufferers to avoid social situations like eating out in restaurants, going to the movies (due to popcorn munching) and thus they experience loneliness and isolation even within their home.

A good overview of the problems faced by the sufferers is provided in the very popular Twenty Thousand Hertz podcast (watch out for trigger sounds in this episode).

Here, I am summarizing the findings of my research which was just published [1] recently that investigated the brain basis (neuropathophysiology) underlying this condition. 

Using non-invasive brain imaging (functional MRI), we investigated the brain activation to sounds and while at rest.

• We see a differential activation in Misophonia sufferers in response to trigger sounds much more than for others sounds in the motor brain, especially the brain area that is involved in representing lip, tongue, and jaw movement (i.e. chewing). This is in addition Anterior Insula as shown in a previous study [2].
• We find increased functional connectivity between the brain area that represents chewing to secondary auditory brain in Misophonia sufferers during perception of any sound.
• We also recorded the metabolic activity of the brain at rest known as resting state fMRI. We found increased functional connectivity during rest in Misophonia sufferers between the brain area that represents chewing and auditory and visual brain areas.

Summary:

• Conventionally, Misophonia has been considered as a disorder of sound emotion processing. 
• Here, we propose a model of Misophonia based on involuntary ‘mirroring’ of action of others. Here, trigger sounds / images activate the part of the brain in Misophonia sufferers as if they are executing the movements themselves. This is known as "mirroring". 
• This involuntary overactivation of the 'mirror' system may lead to either a sense of loss of control or interference in current goals and actions of Misophonia sufferers. Thus this results in anger or irritation.

References:

[1] S Kumar, Pradeep Dheerendra, M Erfanian, E Benzaquen, W Sedley, M Lad, PE Gander, DE Bamiou, TD Griffiths, "The motor basis for Misophonia", Journal of Neuroscience, vol 41(26), pp. 5762-5770, 2021 Link: https://www.jneurosci.org/content/41/26/5762

[2] S Kumar, Olana Tansley-Hancock, William Sedley, Joel S. Winston, Martina F. Callaghan, Micah Allen, Thomas E. Cope, Phillip E. Gander, Doris-Eva Bamiou, and Timothy D. Griffiths. "The brain basis for misophonia." Current Biology 27, no. 4 (2017): 527-533. Link: https://www.cell.com/current-biology/fulltext/S0960-9822(16)31530-5

Comic image copyright (c) Brown Paper Bag