The perturbation paradigm modulates error-based learning in a highly automated task: outcomes in swallowing kinematics

Predictors of Residue and Airway Invasion in Parkinson's Disease

Dysphagia is a highly prevalent disorder in Parkinson's Disease (PD) characterized by changes in swallowing kinematics, residue, and airway invasion. These changes can lead to serious medical morbidities including malnutrition, aspiration pneumonia, and death. However, little is known about the most predictive causes of residue and airway invasion in this patient population. Therefore, the aims of this study were to (1) assess how disease severity affects residue, airway invasion, and swallowing kinematics in PD; and (2) determine which swallowing kinematic variables were most predictive of residue and airway invasion. A secondary analysis of forty videofluoroscopic swallow studies (VFSS) from individuals with early through mid-stage PD was performed. Airway invasion (Penetration-Aspiration Scale 'PAS'), residue (Bolus Clearance Ratio 'BCR'), and ten spatiotemporal swallowing kinematic variables were analyzed. Statistical analyses were used to determine if disease severity predicted residue, depth of airway invasion, and swallowing kinematics, and to examine which swallowing kinematic variables were most predictive of residue and the presence of airway invasion. Results revealed that residue and the presence of airway invasion were significantly predicted by swallowing kinematics. Specifically, airway invasion was primarily influenced by the extent and timing of airway closure, while residue was primarily influenced by pharyngeal constriction. However, disease severity did not significantly predict changes to swallowing kinematics, extent of residue, or depth of airway invasion during VFSS assessment. This study comprehensively examined the pathophysiology underlying dysphagia in people with early to mid-stage PD. The results of the present study indicate that disease severity alone does not predict swallowing changes in PD, and therefore may not be the best factor to identify risk for dysphagia in PD. However, the swallowing kinematics most predictive of residue and the presence of airway invasion were identified. These findings may help to guide the selection of more effective therapy approaches for improving swallowing safety and efficiency in people with early to mid-stage PD.

Effects of Submental Surface Electrical Stimulation on Swallowing Kinematics in Healthy Adults: An Error-Based Learning Paradigm

PURPOSE

Hyoid bone and laryngeal approximation aid airway protection (laryngeal vestibule closure) while moving toward their peak superior and anterior positions during swallowing. Submental surface electrical stimulation (SES) is a therapeutic technique that targets the muscles that move the hyoid bone during swallowing. It is unknown whether submental SES only increases peak hyoid bone swallowing positions but not peak laryngeal swallowing positions, which could require faster or greater laryngeal movement to achieve adequate laryngeal vestibule closure.

METHOD

We examined the effects of submental SES on hyo-laryngeal kinematics in 30 healthy adults who swallowed 50 times using an error-based learning paradigm.

RESULTS

Submental SES did not alter any hyo-laryngeal swallowing kinematic. However, submental SES significantly changed the starting position of the hyoid bone just prior to the swallow onset (more anterior; p = .003). On average, submental SES immediately prior to swallow onset can position the hyoid approximately 20% closer to its peak swallowing point.

CONCLUSIONS

These findings indicate that electrical stimulation of the agonists for hyoid movement might not alter swallowing outcomes tested in this study. However, submental SES could have clinical utility by minimizing swallowing impairments related to reduced hyoid swallowing range of motion in individuals with dysphagia.

"Hidden in Plain Sight": A Descriptive Review of Laryngeal Vestibule Closure

A major emphasis in the evaluation of swallowing is to identify physiological abnormalities in swallowing that contribute to or explain unsafe swallowing (i.e., ingested material enters the trachea; post-swallow residue in the pharynx). Impairments in laryngeal vestibule closure are widely recognized as one of the major causes of unsafe swallowing, as it is the primary mechanism and first line of defense for preventing material from penetrating the airway during swallowing. However, this complex mechanism is often overlooked and understudied in swallowing research and dysphagia management. The purpose of this review is to promote a better understanding of the mechanism of laryngeal vestibule closure. We discuss where gaps in research exist and propose future directions for incorporating laryngeal vestibule closure as a primary outcome measure in swallowing research. Additionally, we propose that an increased knowledge of the mechanism of laryngeal vestibule closure will increase diagnostic accuracy and optimize dysphagia management for patients with dysphagia.

Motor transfer from the corticospinal to the corticobulbar pathway

There are multiple descending neural pathways, including the corticospinal pathway (CS) and the corticobulbar pathway (CB). The corticospinal pathway has been shown to exhibit within-pathway (CS-to-CS) motor transfer. However, motor transfer across each pathway (CS-to-CB or CB-to-CS) has yet to be studied in depth. The aim of the present study was to examine the effects of cross-pathway motor transfer between the ankle (CS) and tongue (CB) after training with a ballistic goal-directed motor task. Twelve healthy participants were recruited for this two-day experimental study. Six participants performed a ballistic goal-directed task with their ankle on Day 1 (ankle dorsiflexion), then tongue on Day 2 (elevate tongue against IOPI). The other 6 participants performed the same task with their tongue on Day 1, then ankle on Day 2. Both the ankle and tongue tasks (50 trials each) required matching force and time to a visual target. Our findings indicate that participants who underwent ankle training on Day 1 exhibited decreased tongue force error on Day 2 compared with participants who completed the tongue training on Day 1, with no prior ankle training (p = 0.02) (i.e. greater accuracy). This finding suggests that cross-pathway transfer from the corticospinal pathway to the corticobulbar pathway occurred with respect to force error. In other words, training of the ankle (CS) translated to improved training performance of the tongue (CB) through a reduction in force error. However, the reverse was not true - training the tongue did not elicit improved performance of the ankle. Nonetheless, if training with the corticospinal pathway can lead to improved corticobulbar pathway functioning, incorporating multi-pathway rehabilitation techniques might be valuable for clinicians across medical disciplines.

The effect of transcutaneous neuromuscular electrical stimulation on laryngeal vestibule closure timing in swallowing

Background

The purpose of this study was to investigate the effect of transcutaneous neuromuscular electrical stimulation (NMES) on the timing of laryngeal vestibule closure during the pharyngeal stage of swallowing in healthy adults. The theoretical framework proposed that NMES applied to these muscles would present a perturbation to laryngeal vestibular closure reaction time (the amount of time for the laryngeal vestibule to close once the swallowing reflex has been triggered) by providing an antagonistic force to the direction of vestibule closure.

Methods

Nine healthy adults (2 males, 7 females) received ten consecutive stimulations applied to the submandibular hyolaryngeal muscles while performing dry swallows. Laryngeal vestibule closure reaction time (LVCrt) and the laryngeal vestibule closure duration (LVCd) were measured from videoflouroscopic images pre-stimulation and post-stimulation.

Results

Results indicated a significant effect of stimulation on LVCrt but not LVCd. LVCrt was significantly reduced (timing was faster) during swallows immediately after stimulation compared to pre-stimulation.

Conclusions

Findings from this study support the supposition that laryngeal muscles respond to perturbations via adaptation learning, which might be used for rehabilitation of neuromuscular swallowing impairment. This pilot study supports the need for further research.

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

Swallowing maneuvers are routinely trained in dysphagia rehabilitation with the assumption that practiced behaviors transfer to functional swallowing, however transfer is rarely examined in the deglutition literature. The goal of this study was to train the volitional laryngeal vestibule closure (vLVC) maneuver, which is a swallowing maneuver that targets prolonged laryngeal vestibule closure (LVC). In two different training experiments, 69 healthy adults underwent Long-hold (hold vLVC as long as possible) or Short-hold vLVC training (hold vLVC for 2s). Before and after vLVC training, natural swallows (swallowing without a therapeutic technique) were completed. The outcome variables included laryngeal vestibule closure reaction time and the duration of laryngeal vestibule closure. Results indicate that during both Long-hold and Short-hold vLVC trainings, vLVC swallows had faster laryngeal vestibule closure reaction times and longer durations of laryngeal vestibule closure than in pre-training 5ml liquid swallows. However, only faster laryngeal vestibule closure reaction times transferred to post-training 5ml liquid swallows (20-24% faster), but not prolonged durations of laryngeal vestibule closure. Our findings suggest that swallowing maneuver training has the potential to induce transfer of what was practiced to functional swallowing behavior, although not all practiced behaviors may generalize. These findings are significant for bolstering the effectiveness of dysphagia management in medical settings and should be tested in individuals with dysphagia.

Effects of chin-up posture on the sequence of swallowing events

BACKGROUND

Chin-up posture is frequently used to manage oral dysphagia after head and neck cancer. This prospective study investigates the effects of chin-ups on the sequence of pharyngeal swallowing events.

METHODS

Twelve healthy young adults performed 45 consecutive swallows of 5 mL water across 3 phases on videofluoroscopy: 5 swallows in the neutral head position; 30 swallows during chin-up posture; and 10 swallows in the neutral head position. Swallowing kinematic and bolus flow measures for 9 swallowing events were recorded. Linear trends were analyzed across 30 chin-up swallows; pairwise comparison was used to compare the 3 phases.

RESULTS

Time to hyoid peak and laryngeal vestibule closure changed abruptly during chin-up swallowing compared to the initial neutral position. No measure changed across 30 chin-up swallows. Time of hyoid burst decreased upon returning to the neutral position.

CONCLUSION

Our findings indicate that chin-up posture challenges the pharyngeal sequence of events for both swallowing kinematics and bolus flow. © 2017 Wiley Periodicals, Inc. Head Neck 39: 947-959, 2017.