Evidence that an internal schema adapts swallowing to upper airway requirements

Abstract

Hyoid and laryngeal movements contribute to laryngeal vestibule closure and upper oesophageal sphincter opening during swallowing. Evidence of an internal sensorimotor scaling system allowing individuals to achieve these functional goals is lacking. In speech, speakers adjust their articulatory movement magnitude according to the movement distance required to reach an articulatory target for intelligible speech. We investigated if swallowing is similar in that movement amplitude may be scaled by the functional goal for airway protection during swallowing, rather than by head and neck size. We hypothesized that healthy individuals adapt to their own anatomy by adjusting hyo-laryngeal movements to achieve closure of the upper airway. We also investigated if individuals would automatically compensate for changes in their initial hyo-laryngeal positions and area when head position was changed prior to swallowing. Videofluoroscopy was performed in 31 healthy adults. Using frame-by-frame motion analysis, anterior and superior hyoid and laryngeal displacement, and hyo-laryngeal area were measured prior to and during swallowing. Kinematic measurements during swallowing were examined for relationships with pharyngeal neck length, and initial hyo-laryngeal positions, length and area before swallowing. During swallowing, individuals altered laryngeal elevation magnitude to exceed hyoid elevation based on hyo-laryngeal length before swallowing. Anterior laryngeal displacement was related to initial larynx distance from the spine, while hyoid elevation was predicted by pharyngeal neck length and initial hyoid distance from the mandible prior to the swallow. In conclusion, individuals automatically adapt hyo-laryngeal movement during swallowing based on targets required for closing the hyo-laryngeal area for safe swallowing.

Impact of recurrent laryngeal nerve lesion on oropharyngeal muscle activity and sensorimotor integration in an infant pig model

“…Another potential mechanism for these changes lies in feedforward models of neural control of swallowing (32,33). Wong et al (58) suggest that in adult humans laryngeal elevation, an important component of swallowing, is responsive to changes in airway opening before the swallow. They conclude that internal sensorimotor adaptation occurs in response to changing demands for airway protection.…”

Examination of swallowing maneuver training and transfer of practiced behaviors to laryngeal vestibule kinematics in functional swallowing of healthy adults

“…This theory could explain our findings where LVCrt was faster, but dLVC was unchanged in natural swallows after vLVC training, which was a surprising outcome (Wong, Domangue, Fels, & Ludlow, 2016). We hypothesized that successful prolongation of dLVC during training would transfer to dLVC during post-training saliva and bolus swallows.…”

“…Earlier LVC onset indicates that participants were able to identify the particular swallowing mechanic that required modification prior to swallowing onset. Perhaps this outcome is supported by theories presented by Wong et al (2016), where achieving target behaviors of LVC mechanics occur prior to the swallow. It is also supported by theories of implicit learning and reflexive learning (Bastian, 2008; Chandrasekaran, Yi, & Maddox, 2014), wherein what was learned cannot be explicitly verbalized or is largely unknown, but has been shown to lead to after-effects in swallowing airway protection kinematics in healthy adults (Anderson et al, 2015; Calvo et al, 2017; Humbert et al, 2015; Humbert, Christopherson, et al, 2012; Humbert, Lokhande, Christopherson, German, & Stone, 2012).…”

“…Wong et al (2016) introduced the notion that the structures involved in LVC predict their distance from one another prior to swallowing to plan appropriate movements to close the airway during the swallow. This theory could explain our findings where LVCrt was faster, but dLVC was unchanged in natural swallows after vLVC training, which was a surprising outcome (Wong, Domangue, Fels, & Ludlow, 2016).…”

A review of the approaches to predict the ease of swallowing and post-swallow residues

“…Both reflexive (or automic) and volitive (voluntary) behaviors concur to control swallowing (Ertekin, 2011). Wong et al (Wong et al, 2017) showed that the trajectory of the hyoid bone and the extent of larynx elevation in different subjects are adapted to maximize airway protection. The pressures generated in the velopharynx were found to be dependent on the body position (Rosen et al, 2017).…”