Why you hate the sound of chewing or a pen clicking repeatedly

Ever wondered why the sound of people chewing food, breathing off, a pen clicking repeatedly irritate you? It may be because of an abnormality in the emotional control mechanism which causes the brain to go into overdrive on hearing such trigger sounds, say researchers led by one of Indian-origin.

The findings showed that the brains of people with such condition -- known as misophonia or hatred of trigger sounds -- showed a physical difference in the frontal lobe between the cerebral hemispheres -- with higher myelination in the grey matter of ventromedial prefrontal cortex (vmPFC).

"For many people with misophonia...for the first time we have demonstrated a difference in brain structure and function in sufferers," said Sukhbinder Kumar at Newcastle University in Britain.

Further, the study, published in the journal Current Biology, also showed abnormal connections between this frontal-lobe area and an area called the anterior insular cortex (AIC) -- known to be involved in processing emotions and integrating signals both from the body and outside world.

In misophonic participants, the trigger sounds increased activity in both brain areas, while in normal participants, the increase was seen only in the AIC, not in the frontal area.

This reflects an abnormality of a control mechanism between the frontal lobe and AIC, the researchers said.

"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," added Tim Griffiths, professor at Newcastle University.

The trigger sound was also found to evoke a heightened physiological response with increased heart rate and sweating in people with misophonia, the researchers noted.

--IANS

rt/ksk/vt