The Neurochemistry of Decreased Sound Tolerance: A Magnetic Resonance Spectroscopy (MRS) study of Misophonia and Hyperacusis

This study examined the concentrations of excitatory and inhibitory neurotransmitters (glutamate and GABA respectively) in two regions of interest (auditory and insular cortices) and a control region (visual cortex) to test the hypothesis that decreased sound tolerance would be linked to increased cortical excitability (more glutamate and/or less GABA). Misophonia (negative emotional responses to specific sounds) and hyperacusis (finding sounds atypically loud) were separately considered and key comorbidities excluded (tinnitus, migraine, autism). A MEGA-PRESS sequence was used for auditory cortex to optimise the detection of GABA. We found no significant group differences in neurotransmitter in any region and pre-registered Bayesian analyses suggested that these are sensitive null results. By contrast, we found increased brain volumes in the auditory cortex (for both misophonia and hyperacusis) and insula (misophonia only). These findings argue against the idea that decreased sound tolerances are linked to neurochemically-driven differences in excitation/inhibition but support the conclusion that they are linked to structural brain differences.