We tested two hypotheses using surface electrical stimulation in chronic pharyngeal dysphagia: that stimulation 1) lowered the hyoid bone and/or larynx when applied at rest, and 2) increased aspiration, penetration or pharyngeal pooling during swallowing. Bipolar surface electrodes were placed on the skin overlying the submandibular and laryngeal regions. Maximum tolerated levels of stimulation were applied while patients held their mouth closed at rest. Videofluoroscopic recordings were used to measure hyoid movements in the superior-inferior (s-i) and anterior-posterior (a-p) dimensions and the subglottic air column (s-i) position while stimulation was on and off. Patients swallowed 5 ml liquid when stimulation was off, at low sensory stimulation levels, and at maximum tolerated levels (motor). Speech pathologists blinded to condition, tallied the frequency of aspiration, penetration, pooling and esophageal entry from videofluorographic recordings of swallows. Only significant (p=0.0175) hyoid depression occurred during stimulation at rest. Aspiration and pooling were significantly reduced only with low sensory threshold levels of stimulation (p=0.025) and not during maximum levels of surface electrical stimulation. Those patients who had reduced aspiration and penetration during swallowing with stimulation had greater hyoid depression during stimulation at rest (p= 0.006). Stimulation may have acted to resist patients' hyoid elevation during swallowing.

Surface electrical stimulation is currently used in therapy for swallowing problems, although little is known about its physiological effects on neck muscles or swallowing. Previously, when one surface electrode placement was used in dysphagic patients at rest, it lowered the hyolaryngeal complex. Here we examined the effects of nine other placements in normal volunteers to determine 1) whether movements induced by surface stimulation using other placements differ, and 2) whether lowering the hyolaryngeal complex by surface electrical stimulation interfered with swallowing in healthy adults. Ten bipolar surface electrode placements overlying the submental and laryngeal regions were tested. Maximum tolerated stimulation levels were applied at rest while participants held their mouths closed. Videofluoroscopic recordings were used to measure hyoid bone and subglottic air column (laryngeal) movements from resting position and while swallowing 5 ml of liquid barium, with and without stimulation. Videofluoroscopic recordings of swallows were rated blind to condition using the National Institutes of Health-Swallowing Safety Scale. Significant (P < 0.0001) laryngeal and hyoid descent occurred with stimulation at rest. During swallowing, significant (P

Phonation is defined as a laryngeal motor behavior used for speech production, which involves a highly specialized coordination of laryngeal and respiratory neuromuscular control. During speech, brief periods of vocal fold vibration for vowels are interspersed by voiced and unvoiced consonants, glottal stops and glottal fricatives (/h/). It remains unknown whether laryngeal/respiratory coordination of phonation for speech relies on separate neural systems from respiratory control or whether a common system controls both behaviors. To identify the central control system for human phonation, we used event-related fMRI to contrast brain activity during phonation with activity during prolonged exhalation in healthy adults. Both whole-brain analyses and region of interest comparisons were conducted. Production of syllables containing glottal stops and vowels was accompanied by activity in left sensorimotor, bilateral temporoparietal and medial motor areas. Prolonged exhalation similarly involved activity in left sensorimotor and temporoparietal areas but not medial motor areas. Significant differences between phonation and exhalation were found primarily in the bilateral auditory cortices with whole brain analysis. The ROI analysis similarly indicated task differences in the auditory cortex with differences also detected in the inferolateral motor cortex and dentate nucleus of the cerebellum. A second experiment confirmed that activity in the auditory cortex only occurred during phonation for speech and did not depend upon sound production. Overall, a similar central neural system was identified for both speech phonation and voluntary exhalation that primarily differed in auditory monitoring. Keywords phonation; exhalation; speech; fMRI Phonation for human speech is a highly specialized manner of laryngeal sensorimotor control that extends beyond generating the sound source of speech vowels and semi-vowels (e.g. /y/ and /r/). Laryngeal gestures for voice onset and offset distinguish voiced and unvoiced consonant pairs through precise timing of voice onset (Raphael et al., 2006). Brief interruptions in phonation by glottal stops (/ʔ/) mark word and syllable boundaries through hyper-adduction of the vocal folds to offset phonation. Each of these vocal fold gestures, in addition to rapid pitch changes for intonation require precisely controlled variations in intrinsic laryngeal activity (Poletto et al., 2004). To understand the neural control of phonation for speech, laryngeal control must be investigated independent of the oral articulators (lips, tongue, jaw). Several neuroimaging studies of phonation for speech included oral articulatory movements Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the producti...

Volitional swallowing in humans involves the coordination of both brainstem and cerebral swallowing control regions. Peripheral sensory inputs are necessary for safe and efficient swallowing, and their importance to the patterned components of swallowing has been demonstrated. However, the role of sensory inputs to the cerebral system during volitional swallowing is less clear. We used four conditions applied during functional magnetic resonance imaging to differentiate between sensory, motor planning, and motor execution components for cerebral control of swallowing. Oral air pulse stimulation was used to examine the effect of sensory input, covert swallowing was used to engage motor planning for swallowing, and overt swallowing was used to activate the volitional swallowing system. Breath-holding was also included to determine whether its effects could account for the activation seen during overt swallowing. Oral air pulse stimulation, covert swallowing and overt swallowing all produced activation in the primary motor cortex, cingulate cortex, putamen and insula. Additional regions of the swallowing cerebral system that were activated by the oral air pulse stimulation condition included the primary and secondary somatosensory cortex and thalamus. Although air pulse stimulation was on the right side only, bilateral cerebral activation occurred. On the other hand, covert swallowing minimally activated sensory regions, but did activate the supplementary motor area and other motor regions. Breath-holding did not account for the activation during overt swallowing. The effectiveness of oral-sensory stimulation for engaging both sensory and motor components of the cerebral swallowing system demonstrates the importance of sensory input in cerebral swallowing control.