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Finger position sense is a proprioceptive modality highly important for fine motor control. Its developmental time course is largely unknown. This cross-sectional study examined its typical development in 138 children (8–17 years) and a group of 14 healthy young adults using a fast and novel psychophysical test that yielded objective measures of position sense acuity. Participants placed their hands underneath a computer tablet and judged the perceived position of their unseen index finger relative to two visible areas displayed on a tablet following a two-forced-choice paradigm. Responses were fitted to a psychometric acuity function from which the difference between the point-of-subjective-equality and the veridical finger position (ΔPSE) was derived as a measure of position sense bias, and the uncertainty area (UA) as a measure of precision. The main results are: First, children under 12 exhibited a significantly greater UA than adults while adolescent children (13–17 years) exhibited no significant differences when compared to adults. Second, no significant age-related differences in ΔPSE were found across the age range of 8–17 years. This implies that the typical development of finger position sense from late childhood to adulthood is characterized as an age-dependent increase in proprioceptive precision and not as a decrease in bias. [ABSTRACT FROM AUTHOR]

• Inhibition of slow motor cortical rhythms during vocalization is reduced in spasmodic dysphonia. • Somatosensory-motor cortical synchrony during vocalization is excessive in spasmodic dysphonia. • Abnormal cortical processing in spasmodic dysphonia is mainly lateralized in the left hemisphere. 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. Ten SD individuals and 10 healthy volunteers produced 50 vowel vocalization epochs of 2500 ms duration. Two EEG features were derived: (1) event-related change in spectral power during vocalization relative to rest, (2) inter-regional spectral coherence. During early vocalization (500–1000 ms) the SD group showed significantly larger alpha band spectral power over the left motor cortex. During late vocalization (1000–2500 ms) SD patients showed a significantly larger gamma band coherence between left somatosensory and premotor cortical areas. 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. 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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]