title: The capacity for volitional control of pharyngeal swallowing in healthy adults.
abstract: BACKGROUND
  Previous research has documented that pressure and duration of brainstem-generated pharyngeal swallowing can be cortically modulated. But there is a commonly held belief that the sequence of pharyngeal pressure remains constant. However, Huckabee et al. [19] reported a patient cohort who demonstrated reduced latency of peak pressure in the proximal and distal pharynx, disproportionate and sometimes inversely correlated with overall swallowing duration, suggesting independent timing of underlying muscle contraction within the overall pharyngeal response. This study examined if healthy adults can volitionally produce altered latency of pharyngeal closure in isolation following intensive training, thereby evaluating the capacity for pharyngeal adaptation in a healthy system.
  
  
  METHODS
  Six healthy participants were seen for intensive training, consisting of daily one-hour sessions over two weeks (10 days) using pharyngeal manometry as a visual biofeedback modality. The participants were instructed to produce simultaneous pressure in the pharyngeal sensors when swallowing. The temporal separation of peak proximal and distal pharyngeal pressure was measured with discrete-sensor pharyngeal manometry at baseline, during training with biofeedback, and following training without biofeedback.
  
  
  RESULTS
  Following intensive training, participants were able to reduce temporal separation of peak pressure between the proximal and distal pharyngeal sensors from a baseline median of 188 ms (IQR=231 ms) to 68 ms (IQR=92 ms; p=0.002). In contrast, there was no significant change in overall swallowing duration during training (p=0.41). However, change in pharyngeal pressure latency was moderately correlated with both change in swallowing duration (r=0.444) and amplitude (r=0.571) during training, and there was a reduction in swallowing duration post-training (p=0.03).
  
  
  CONCLUSIONS
  Given intensive manometric biofeedback training, participants substantially reduced temporal separation of peak proximal and distal pharyngeal pressure when volitionally swallowing. However, correlation with overall pressure and duration measures suggest the adaptation was one of modulating the cumulative pharyngeal response rather than altering discrete components of timing of pharyngeal pressure in isolation. This is inconsistent with the pattern of behaviour documented by Huckabee et al. [19] in the patient population. Further research on modulatory control over targeted aspects of the pharyngeal swallow is needed, and may provide avenues for rehabilitative treatment of patients with dysphagia.
authors.affiliation: The University of Canterbury Rose Centre for Stroke Recovery and Research, Christchurch, New Zealand; Department of Communication Disorders, University of Canterbury, Christchurch, New Zealand; New Zealand Brain Research Institute, Christchurch, New Zealand. Electronic address: kristin.lamvik@pg.canterbury.ac.nz.
authors.forename: Kristin
authors.initials: K
authors.lastname: Lamvik
authors.affiliation: The University of Canterbury Rose Centre for Stroke Recovery and Research, Christchurch, New Zealand; Department of Communication Disorders, University of Canterbury, Christchurch, New Zealand; New Zealand Brain Research Institute, Christchurch, New Zealand; Department of Medical Physics & Bioengineering, Christchurch Hospital, Christchurch, New Zealand.
authors.forename: Richard
authors.initials: R
authors.lastname: Jones
authors.affiliation: Department of Communication Disorders, University of Canterbury, Christchurch, New Zealand; New Zealand Brain Research Institute, Christchurch, New Zealand.
authors.forename: Sonja
authors.initials: S
authors.lastname: Sauer
authors.affiliation: The University of Canterbury Rose Centre for Stroke Recovery and Research, Christchurch, New Zealand; Department of Communication Disorders, University of Canterbury, Christchurch, New Zealand; New Zealand Brain Research Institute, Christchurch, New Zealand.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Erfmann
authors.affiliation: The University of Canterbury Rose Centre for Stroke Recovery and Research, Christchurch, New Zealand; Department of Communication Disorders, University of Canterbury, Christchurch, New Zealand; New Zealand Brain Research Institute, Christchurch, New Zealand.
authors.forename: Maggie-Lee
authors.initials: ML
authors.lastname: Huckabee
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D000223:Adaptation, Psychological / Q000502:physiology; D000328:Adult; D001676:Biofeedback, Psychology; D003679:Deglutition / Q000502:physiology*; D005260:Female; D006801:Humans; D007858:Learning / Q000502:physiology*; D008297:Male; D008365:Manometry; D009043:Motor Activity / Q000502:physiology*; D010614:Pharynx / Q000502:physiology*; D011312:Pressure; D014836:Volition / Q000502:physiology; D055815:Young Adult
keywords: Biofeedback; Deglutition; Dysphagia; Motor learning; Pharyngeal manometry