Misophonia is a condition where people have extreme distress towards everyday bodily sounds like eating, chewing, breathing etc which are called trigger sounds. I am investigating the neuropathophysiology underlying this condition. Here are a couple of projects that I worked on:
Brain activation to trigger sounds
- In addition to Left Anterior Insula as reported in Sukhbinder Kumar, et. al., Curr. Biol. (2017), we also find Motor and somatosensory areas show increased activation in Misophonics compared to matched healthy controls in response to any sounds.
- Further we see a differential brain activation in response to trigger sounds over aversive or neutral sounds more so in Misophonia subjects than matched controls in these sensory-motor brain regions especially the brain area that is involved in representing lip, tongue and jaw movement.
Sound Evoked Response
Motor and somatosensory brain areas show increased activation in Misophonia subjects compared to controls in response to sounds.
Activation to sound types
There is a differential brain activation in response to trigger sounds over aversive / neutral sounds more so in Misophonics than controls in (B) motor and (C) somatosensory regions esp. (D) area representing chewing.
Functional Connectivity during sound perception
- We found that the functional connectivity of secondary auditory cortex (right Planum Temporale) to motor cortex is higher in Misophonia subjects than matched controls during perception of all kinds of sounds (trigger, aversive, and neutral sounds).
- We also found that the functional connectivity of brain area representing lip, tongue, jaw movement to secondary auditory cortex (right PT) is higher in Misophonia subjects than matched controls during perception of any kind of sounds.
Sound triggered network
Secondary auditory cortex (right PT) has enhanced functional connectivity to bilateral motor cortex in response to any kind of sound.
Chewing area connections
Brain area representing chewing has enhanced functional connectivity to secondary auditory cortex in response to any kind of sound.
Resting state Functional Connectivity
Using non-invasive fMRI modality, we recorded the metabolic activity of the brain at rest (resting state fMRI) in both Misophonic subjects and matched healthy controls. We found increased functional connectivity in Misophonia subjects than healthy controls between:
- Secondary interoceptive brain (Left anterior Insula) with Motor brain areas (left Motor cortex and right Cerebellum)
- Auditory brain (Right Planum Temporale) with the brain area that represents chewing (right Motor cortex)
- Two core nodes of the default mode network (posterior Cingulate Cortex and ventro-medial Pre Frontal cortex)
The secondary interoceptive brain area has increased functional connectivity with the motor brain areas in Misophonics than Controls
Auditory brain and Chewing area
The secondary auditory cortex has increased functional connectivity with the brain area that represents jaw, lip, and tongue movement in Misophonics than Controls
Core Default Mode Network
Left anterior Insula does not have a differential connectivity with the brain regions that are connected at rest (DMN) though the DMN itself has increased functional connectivity in Misophonics than Controls
Heart Rate variability and Functional Connectivity
A good variability in heart rate is important physiologically. We observed reduced heart rate variability in Misophonics compared to controls. This was found by evaluating RMSSD, the variation in the change in the inter-beat-interval.
This physiological variable was positively correlated with resting state functional connectivity between left anterior Insula and motor cortex (SMA) in Misophonics while negatively correlated in matched healthy controls.
Interoception in Misophonics
Interoception concerns with the ability of the brain to receive, integrate, process, be aware of the physiological signals from the body like heart beat, breathing, etc. We hypothesise that interoceptive abilities are different in Misophonia subjects than healthy controls.
To assess brain basis underlying interoception, we recorded the metabolic activity of the brain, using non-invasive fMRI modality, in both Misophonia subjects and matched healthy controls during two tasks: first an interoceptive task of heart beat counting, and second, an sensory task of counting visual gratings.
We analysed the brain activity during interoceptive and sensory tasks, and found that:
- In Misophonics, the change in the brain activity within the secondary interoceptive brain (Left Anterior Insula) between an interoceptive (heart beat counting) task vs sensory (visual) tasks is different from those seen in healthy controls.
In Misophonics, the change in the brain activity within the secondary interoceptive brain (Left Anterior Insula) between an interoceptive (heart beat counting) task vs sensory (visual) tasks is different from those seen in healthy controls.
Connectivity during Interoception
During an interoceptive task, the primary interoceptive brain region increases its connectivity with the secondary interoceptive brain region while decreasing with the sensory regions.
Connectivity in Misophonics
In Misophonics, the change in the functional connectivity within the interoceptive brain between an interoceptive vs sensory tasks is different from those seen in healthy controls.
We analysed the functional connectivity during interoceptive and sensory tasks in Misophonia subjects and controls, and found that:
- During heart beat counting (interoceptive) task, the primary interoceptive brain area (Left Posterior Insula) region increases its functional connectivity with the secondary interoceptive brain area (Right Anterior Insula) while decreasing its connectivity with the sensory regions (visual occipital cortex).
- Further, this change in the functional connectivity within the interoceptive brain (Insula) between an interoceptive task (heart beat counting) vs sensory task (visual) is different in Misophonia subjects compared to those seen in healthy controls.