Objective: Spasmodic dysphonia (SD) is a debilitating voice/speech disorder without an effective cure. To obtain a better understanding of the underlying cortical neural mechanism of the disease we analyzed electroencephalographic (EEG) signals of people with SD during voice production.Method: Ten SD individuals and 10 healthy volunteers produced 50 vowel vocalization epochs of 2500ms duration. Two EEG features were derived: (1) event-related change in spectral power during vocalization relative to rest, (2) inter-regional spectral coherence.Results: During early vocalization (500-1000ms) the SD group showed significantly larger alpha band spectral power over the left motor cortex. During late vocalization (1000-2500ms) SD patients showed a significantly larger gamma band coherence between left somatosensory and premotor cortical areas. Conclusions:Two atypical patterns of cortical activity characterize the pathophysiology of spasmodic dysphonia during voice production: (1) a reduced movement-related desynchronization of motor cortical networks, (2) an excessively large synchronization between left somatosensory and premotor cortical areas. Significance:The pathophysiology of SD is characterized by an abnormally high synchronous activity within and across cortical neural networks involved in voice production that is mainly lateralized in the left hemisphere.

Spasmodic dysphonia (SD) is an incurable focal dystonia of the larynx that impairs speech and communication. Vibro-tactile stimulation (VTS) alters afferent proprioceptive input to sensorimotor cortex that controls speech. This proof-of-concept study examined the effect of laryngeal VTS on speech quality and cortical activity in 13 SD participants who vocalized the vowel /a/ while receiving VTS for 29 minutes. In response to VTS, 9 participants (69%) exhibited a reduction of voice breaks and/or a meaningful increase in smoothed cepstral peak prominence, an acoustic measure of voice/speech quality. Symptom improvements persisted for 20 minutes past VTS. Application of VTS induced a significant suppression of theta band power over the left somatosensory-motor cortex and a significant rise of gamma rhythm over right somatosensory-motor cortex. Such suppression of theta oscillations is observed in patients with cervical dystonia who apply effective sensory tricks, suggesting that VTS in SD may activate a similar neurophysiological mechanism. Results of this feasibility study indicate that laryngeal VTS modulates neuronal synchronization over sensorimotor cortex, which can induce short-term improvements in voice quality. The effects of long-term VTS and its optimal dosage for treating voice symptoms in SD are still unknown and require further systematic study.

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Proprioceptive afferents from the ankle joint are essential feedback for maintaining balance. However, there is no widely accepted test or measurement system available for determining the proprioceptive accuracy of the human ankle joint. Here, we present a system with a novel hardware design that applies an established psychometric testing protocol that generates a Just-Noticeable-Difference (JND) threshold as a measure of ankle proprioceptive acuity at the end of testing. To establish the system validity, twelve healthy adult participants completed the assessment. Testing required 25 trials and took approximately 10 minutes to complete. We show exemplar data of the ankle JND threshold and the summary results for all twelve participants. This assessment has the potential to become a tool for clinicians to identify proprioceptive impairment at the ankle and to assess the efficacy of sensorimotor interventions for improving balance in clinical populations.

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