Chewing Well Modulates Pharyngeal Bolus Transit During Swallowing in Healthy Participants

Area of Science:

• Neuroscience
• Physiology
• Gastroenterology

Background:

• Mastication is a complex motor act controlled by the brainstem's central pattern generator, subject to volitional modulation.
• Understanding the interplay between chewing and swallowing is crucial for optimizing oral intake and preventing dysphagia.

Purpose of the Study:

• To investigate the impact of a "chewing well" task on bolus transport and swallowing movements.
• To determine how different food volumes influence the effects of intentional chewing on swallowing physiology.

Main Methods:

• Twenty-six healthy participants performed chewing freely (CF) and chewing well (CW) tasks with varying food volumes (8, 12, 16g) of rice mixed with barium sulphate.
• Videofluoroscopy and electromyography (EMG) of masticatory and swallowing muscles (masseter, suprahyoid, thyrohyoid) were used to assess bolus transport and muscle activity.
• Chewing time and pharyngeal transit time (PTT) were measured for reproducibility.

Main Results:

• Pharyngeal transit time (PTT) showed significant differences between CF and CW conditions, being shorter for CW at 12g and longer at 16g.
• In the 12g condition, the CW task enhanced pharyngeal bolus velocity and reduced thyrohyoid EMG activity during swallowing compared to CF.
• For the 16g condition, increased swallowed bolus volume under CW correlated positively with longer upper esophageal sphincter transit duration.

Conclusions:

• The "chewing well" task modulates pharyngeal transit time during swallowing in a manner dependent on the mouthful volume.
• Intentional chewing can alter bolus transit dynamics and muscle activation patterns, suggesting a volitional influence on the mastication-swallowing sequence.
• Further research is needed to elucidate the precise neural mechanisms and clinical implications of this volitional modulation.