Effects of nasal obstruction on prefrontal cortex activities during chewing

ABSTRACT Purpose: This study was conducted to clarify the effects of experimentally induced nasal obstruction (NO) on prefrontal activation and jaw movement activities, as well as feelings of discomfort and dyspnoea during chewing. Methods and materials: Eighteen healthy volunteers were enrolled as subjects. The levels of awareness of discomfort and sense of dyspnoea with nasal breathing (NB) and NO were determined using a visual analogue scale (VAS) following chewing and imagery tasks. Masticatory movements were analysed for masticatory path width, cycle duration, masticatory velocity, number of masticatory cycles, and duration of pre-swallowing phase during mastication in the subjects with establishment of NO and NB. An FNIRS device (Hb131S, astem Inc., Japan) was used to measure prefrontal cortex activities. Results: Discomfort and feelings of dyspnoea under the NO condition were significantly increased as compared with NB. Also, cycle duration with NO was significantly increased as well as the number of masticatory cycles, whereas those in the pre-swallowing phase were significantly decreased as compared to NB. Furthermore, prefrontal activities during chewing with NO were significantly decreased as compared to NB. Conclusion: These results indicate that nasal obstruction during chewing may induce a decline in prefrontal activities, accompanied with deterioration comfort and dyspnoea, and modulated jaw movement activities.