Altered sensory system activity and connectivity patterns in adductor spasmodic dysphonia

Area of Science:

• Neuroscience
• Speech-Language Pathology
• Medical Imaging

Background:

• Adductor-type spasmodic dysphonia (ADSD) is characterized by effortful speech, often temporarily improved by botulinum neurotoxin type A (BoNT-A).
• Previous research identified structural, phonation, resting-state sensorimotor, and peripheral tactile abnormalities in ADSD patients.

Purpose of the Study:

• To investigate abnormal central tactile processing patterns in ADSD.
• To determine the spatial relationship between these tactile processing abnormalities and dysfunctional resting-state connectivity.
• To assess the responsiveness of these central nervous system patterns to BoNT-A treatment.

Main Methods:

• Functional MRI (fMRI) was conducted on 14/12 ADSD patients (before and during BoNT-A effect) and 15 controls.
• fMRI assessed brain activity during tactile stimulation of the face/hand and during rest.
• Analysis included between-group differences in stimulation-induced activation and resting-state connectivity (regional homogeneity, network connectivity).

Main Results:

• ADSD patients exhibited overactivity in somatosensory areas and higher-order cortical regions contralateral to tactile stimulation before BoNT-A.
• Dysphonia severity correlated with left-hemispheric temporal lobe activity.
• Increased connectivity was observed in the right premotor cortex and left primary auditory cortex, with reduced connectivity at the temporoparietal junction in ADSD patients.
• No significant changes in activation or connectivity were found within patients before and after BoNT-A treatment.

Conclusions:

• Abnormal central somatosensory processing in ADSD supports its classification as a focal dystonia trait.
• Altered tactile processing in the temporal cortex and resting-state connectivity patterns may indicate aberrant cross-modal sensory interactions in ADSD.