title: Behavioural and neurophysiological disruption of corticobulbar motor systems and their effects on sequential pharyngeal swallowing.
abstract: Primary motor networks are known to be involved in the control of voluntary oral movements as well as the modulation of pharyngeal movements during experimentally controlled single swallows performed on command. The role of these networks in the more typical task of sequential swallowing remains unexplored. This study evaluated the hypothesis that experimental disruption of motor cortical activation would reduce the rate and regularity of repeatedly performed volitional or volitionally initiated motor tasks controlled by corticospinal (finger tapping) and corticobulbar (eyebrow movement, jaw opening, volitional sequential swallowing) motor systems, but would not influence a more reflexive corticobulbar task (reflexive sequential swallowing to pharyngeal water infusion). This premise was investigated in 24 healthy participants using two techniques: a dual task paradigm and a transcranial magnetic stimulation paradigm. Disruption effects were quantified by changes in rate and regularity of performance for each tested motor task. In summary, volitional motor tasks controlled by corticospinal motor networks (finger tapping) are more susceptible to behavioural and neurophysiological disruption than tasks controlled by cortiobulbar motor networks containing a reflexive component (both volitional and experimentally initiated consecutive swallowing). Purely volitional motor tasks controlled by the corticobulbar motor system (eyebrow raising or jaw opening) were affected in similar ways as the volitional corticospinal motor tasks. In summary, tasks involving sequential pharyngeal swallowing - whether volitionally or experimentally initiated - are largely robust against disruption of primary cortical motor networks, supporting a key role of medullary CPGs in the motor control of sequential pharyngeal swallowing.
authors.affiliation: New Zealand Brain Research Institute, 66 Stewart Street, Christchurch 8011, New Zealand; Speech and Language Pathology Clinic, Department of Rehabilitation, The Royal Hospital, Muscat, Oman.
authors.forename: Aamir
authors.initials: A
authors.lastname: Al-Toubi
authors.affiliation: Department of Communication Sciences and Disorders, University of Houston, 4455 Cullen Blvd Rm 100, Houston, TX, 77204-6018, United States; Research Service, Michael E. DeBakey VA Medical Center, Houston, TX, 2002 Holcombe Blvd, Houston, TX 7703, United States.
authors.forename: Stephanie K
authors.initials: SK
authors.lastname: Daniels
authors.affiliation: New Zealand Brain Research Institute, 66 Stewart Street, Christchurch 8011, New Zealand; Department of Communication Disorders, The University of Canterbury, Christchurch NZ, Private Bag 4800, Christchurch 8140, New Zealand; Rose Centre for Stroke Recovery and Research, Christchurch NZ, Private Bag 4800, Christchurch 8140, New Zealand.
authors.forename: Maggie-Lee
authors.initials: ML
authors.lastname: Huckabee
authors.affiliation: Department of Psychology, Tulane University, New Orleans, LA, Department of Psychology, Tulane University 2007 Percival Stern Hall, New Orleans, LA 70118, United States.
authors.forename: David M
authors.initials: DM
authors.lastname: Corey
authors.affiliation: Discipline of Speech Pathology, School of Health Sciences, Flinders University, Adelaide, Australia. Electronic address: sebastian.doeltgen@flinders.edu.au.
authors.forename: Sebastian H
authors.initials: SH
authors.lastname: Doeltgen
mesh_terms: D003679:Deglutition / Q000502:physiology*; D004576:Electromyography; D005138:Eyebrows / Q000502:physiology; D005260:Female; D005385:Fingers / Q000502:physiology; D006801:Humans; D007568:Jaw / Q000502:physiology; D008297:Male; D008365:Manometry; D009043:Motor Activity / Q000502:physiology*; D009044:Motor Cortex / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D010614:Pharynx / Q000502:physiology*; D012018:Reflex / Q000502:physiology; D050781:Transcranial Magnetic Stimulation; D014836:Volition / Q000502:physiology; D055815:Young Adult
keywords: Corticobulbar; Disruption; Dual task; Swallowing; Transcranial magnetic stimulation