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For many, sounds made by knuckles breaking, pens clicking or chewing food can be unpleasant or annoying. For a select few, however, these sort of sounds can be simply unbearable — a response which can be a marker for a disorder called misophonia. Now, scientists have discovered how these triggers are processed in the brain and why some of us intensely hate them, yours truly included.

“For many people with misophonia, this will come as welcome news as for the first time we have demonstrated a difference in brain structure and function in sufferers,” said lead researcher Dr Sukhbinder Kumar from the Institute of Neuroscience at Newcastle University and the Wellcome Centre for NeuroImaging at University College London (UCL).

The team from Newcastle University, UK, performed MRI scans on 44 volunteers, half of whom were diagnosed with the misophonia disorder —  a condition in which negative emotions, thoughts, and physical reactions are triggered by specific sounds. The participants’ brains were scanned while they listened to:

• neutral sounds: rain, the clatter of a busy café, a kettle boiling;
• unpleasant sounds: a person screaming or a baby crying;
• trigger sounds: breathing, eating.

Results revealed physical differences in the frontal lobe between the cerebral hemispheres of people with misophonia. Specifically, the researchers recorded abnormal connections between the frontal lobe area and the anterior insular cortex (AIC). The latter brain region is nestled in the side of the brain and is heavily involved in processing emotions.

Misophonic subjects had a heightened activity in both brain regions when they heard the trigger sounds while non-misophonic participants saw activity go up in the AIC but down in the frontal area. It may be that misophonic subjects have an abnormal control mechanism between the frontal lobe and AIC, the researchers from Newcastle claim.

There’s also evidence of greater amounts of myelination, the brain’s insulation, in misophonic subjects. The findings were reported in the journal Current Biology.

“I hope this will reassure sufferers. I was part of the sceptical community myself until we saw patients in the clinic and understood how strikingly similar the features are,” said in a statement Tim Griffiths, Professor of Cognitive Neurology at Newcastle University and UCL.

“We now have evidence to establish the basis for the disorder through the differences in brain control mechanism in misophonia. This will suggest therapeutic manipulations and encourage a search for similar mechanisms in other conditions associated with abnormal emotional reactions,” he added.

According to a 2014 study conducted by researchers from the University of South Florida, 20 percent of the 483 students involved were misophonics. The researchers also found that misophonia symptoms were very similar to those of the psychiatric conditions anxiety, depression, and obsessive-compulsive disorder. In 2013, psychiatrist Arjan Schröder and his colleagues at the University of Amsterdam proposed that misophonia should be classified as a psychiatric disorder in its own right, classed under the OCD spectrum.

Dr. Kumar says that knowing the brain signatures of trigger sounds could enable treatments for misophonics, if they wish so. For instance, a possible treatment would involve a neuro-feedback device which prompts misophonics that they might be reacting a bit overboard.