Abstract
In the present study, the effects of lip closure training were examined in terms of brain activity and oral functions. Nineteen healthy women (22.1±2.9 years old) were randomly assigned to two groups: the training group in which lip closure training was performed for 4 weeks using a mouth rehabilitation apparatus, and the control group in which the training was not performed. Maximum lip closure pressure was measured before and after the training. Furthermore, brain hemodynamic responses (Oxy-Hb concentration) in the whole brain were measured during a lip closure task using this mouth rehabilitation apparatus and during a task in which the subjects were required to keep 50% of the maximum lip closure pressure (50%-pressure task). The results indicated that the maximum lip closure pressure and performance in the 50%-pressure task were improved after the training in the training group. Before the training, mean cortical hemodynamic responses (Oxy-Hb concentration) increased in the prefrontal pole, right and left dorsolateral prefrontal cortex, supplementary motor area, and presupplementary motor area during the lip closure task in both the control and training groups. Furthermore, 4 weeks after the training intervention, the mean cortical Oxy-Hb concentrations in the various prefrontal regions including the prefrontal pole similarly increased during the lip closure task in the training group. However, in the control group, the mean cortical Oxy-Hb concentrations in the prefrontal pole did not increase during the lip closure task 4 weeks after the first measurement. These results suggest that continuous lip closure training improves not only lip closure functions but also higher brain functions by persistent activation of the prefrontal pole.
