Abstract
A bolus of liquid food is usually held and processed in the oral cavity until swallowing. We investigated the influence of liquid bolus viscosity on the duration of the oral stage from food intake to swallowing, and also on the amplitude of the mylohyoid muscle EMG (MH-EMG) at the swallowing recorded by surface electrodes placed on the skin over the mylohyoid muscle, since the MH-EMG indicates the tongue activity when the palate is compressed by the tongue. Eleven healthy volunteers (mean age 25.9) participated. Three liquid samples (SS, starch syrup with a viscosity of 67 Pa s; H, honey with a viscosity of 7.8 Pa s; W, pure water with a viscosity of 0.9 mPa s) were used as test food. Subjects were instructed to swallow 1 ml of each of the three samples placed on the frontal part (F) or middle part (M) of the dorsal surface of the tongue with a syringe. When the samples were placed on the F, the duration of the oral stage was significantly longer for SS than for H and W. But no significant difference in the amplitude of MH-EMG at the swallowing was not obtained among three samples. When the samples were placed on the M, the duration of the oral stage was significantly longer for SS than for H, and the amplitude of MH-EMG at the swallowing was significantly larger for SS than for W. These findings suggest that the viscosity of liquid bolus has a significant effect on the duration of the oral stage, and also that the setting position of the liquid food on the tongue at the food intake has influence on the tongue activity at the swallowing. [J Physiol Sci. 2008;58 Suppl:S196]
