Human hyo-laryngeal movements show adaptive motor learning during swallowing

Abstract

The hyoid bone and larynx elevate to protect the airway during swallowing. However, it is unknown whether hyo-laryngeal movements during swallowing can adjust and adapt to predict the presence of a persistent perturbation in a feed-forward manner (adaptive motor learning). We investigated adaptive motor learning in nine healthy adults. Electrical stimulation was administered to the anterior neck to reduce hyo-laryngeal elevation, requiring more strength to swallow during the perturbation period of this study. We assessed peak hyoid bone and laryngeal movements using videofluoroscopy across 35 5ml-water swallows. Evidence of adaptive motor learning of hyo-laryngeal movements was found when: (1) participants showed systematic, gradual increases in elevation against the force of electrical stimulation, and; (2) hyo-laryngeal elevation overshot the baseline (pre-perturbation) range of motion, showing behavioral after-effects, when the perturbation was unexpectedly removed. Hyolaryngeal kinematics demonstrate adaptive, error-reducing movements in the presence of changing and unexpected demands. This is significant because individuals with dysphagia often aspirate due to disordered hyo-laryngeal movements. Thus, if rapid motor learning is accessible during swallowing in healthy adults, patients may be taught to predict the presence of perturbations and reduce errors in swallowing before they occur.