The motor basis for misophonia

Misophonia is a common disorder characterized by the experience of strong negative emotions of anger and anxiety in response to certain everyday sounds, such as those generated by other people eating, drinking and breathing. The commonplace nature of these 'trigger' sounds makes misophonia a devastating disorder for sufferers and their families. How such innocuous sounds trigger this response is unknown. Since most trigger sounds are generated by orofacial movements (e.g. chewing) in others, we hypothesized that the mirror neuron system related to orofacial movements could underlie misophonia. We analysed resting state fMRI (rs-fMRI) connectivity (N=33, 16 females) and sound-evoked fMRI responses (N=42, 29 females) in misophonia sufferers and controls. We demonstrate that, compared to controls, the misophonia group show no difference in auditory cortex responses to trigger sounds, but do show: (i) stronger rs-fMRI connectivity between both auditory and visual cortex and the ventral pre-motor cortex responsible for orofacial movements; (ii) stronger functional connectivity between the auditory cortex and orofacial motor area during sound perception in general; (iii) stronger activation of the orofacial motor area, specifically, in response to trigger sounds. Our results support a model of misophonia based on 'hyper-mirroring' of the orofacial actions of others with sounds being the 'medium' via which action of others is excessively mirrored. Misophonia is therefore not an abreaction to sounds, per se, but a manifestation of activity in parts of the motor system involved in producing those sounds. This new framework to understand misophonia can explain behavioural and emotional responses and has important consequences for devising effective therapies. Significance Statement Conventionally, misophonia, literally 'hatred of sounds' has been considered as a disorder of sound emotion processing, in which 'simple' eating and chewing sounds produced by others cause negative emotional responses. Our data provide an alternative but complementary perspective on misophonia that emphasizes the action of the trigger-person rather than the sounds which are a by-product of that action. Sounds, in this new perspective, are only a 'medium' via which action of the triggering-person is mirrored onto the listener. This change in perspective has important consequences for devising therapies and treatment methods for misophonia. It suggests that instead of focussing on sounds, which many existing therapies do, effective therapies should target the brain representation of movement.