Abstract
Thickening agents are used in many medical institutions and nursing care facilities to adjust food form and thereby prevent aspiration. Many studies have investigated the effects of a thickening agent-induced changes in food form on laryngeal penetration, aspiration, and pharyngeal residue, but its relationship with brain function is less clear. The purpose of this study was to investigate the effect of beverage thickness on the prefrontal cortex using functional near-infrared spectroscopy. Participants were 42 right-handed women with mean age of 21.4 ± 0.6 years. They were asked to taste three kinds of green tea and juice with different viscosities, with the activity of the prefrontal area during the task recorded by an OEG-16 near-infrared spectroscopy system. The activity of the prefrontal cortex was analyzed by Brain Analyzer software while the participants tasted green tea and juice. The results suggest that a lowering of drink palatability elicited an unpleasant emotion, which was reflected in the activity of the orbitofrontal cortex. In addition, the thickened beverage altered activity in the frontal pole and orbitofrontal cortex. Changes in brain activity seemed to be related to changes in drink palatability, differences in taste, and novelty. We conclude that thickening agents, which are mainly used to prevent aspiration, may be used to induce changes in the activity of the prefrontal cortex, particularly the frontal pole and orbitofrontal cortex. Our results may contribute to the development and clinical application of a new training method for dysphagia rehabilitation using thickening agents and to the prevention of dementia.
https://ror.org/03bwzch55 
