Abstract
Investigating the sequence and magnitude of tongue movements against the hard palate during swallowing is basic to understanding the process by which the bolus is moved from the front of the mouth to the pharynx. Here we outline the basic muscular anatomy of the tongue, and we report on specific pressure patterns generated at three positions along the midline: at the front, middle and back of the hard palate. We show that there are sharp amplitudinal changes from positive to negative pressures at all three locations. While these pressure patterns show large interindividual variations, they appear to be consistent within individuals, irrespective of bolus size or consistency. Tentatively, we are able to identify three basic patterns; Type I, squeezer - a mostly positive pressure cascade from the front to the back of mouth; Type II, slider - characterized by an effortless and extended swallow, and Type III, slapper - large positive and negative pressure fluctuations during each swallow. Finally, we found that the most variability in pressure fluctuations occurred in the front of the mouth, from which we conclude that the front of the tongue has a predominant organisational role, whereas the back of the tongue is mostly propulsional.
PRACTICAL APPLICATIONS
While tongue pressure patterns during liquid swallowing vary greatly between persons, they appear to be highly specific within individuals. While some individuals have seemingly effortless swallows, others are more forceful and either squeeze their bolus or apply rapidly changing positive and negative forces to it. The results presented here also show that these patterns remain conserved irrespective of bolus consistency or volume, suggesting that novel foodstuffs might have to be individually designed with three swallowing types in mind. We also show maximum variation at the front of the tongue, emphasising an organisational rather than purely propulsional role for this area. This knowledge will be useful in designing and formulating new food products, particularly for those suffering from dysphagia, an inability to swallow normally.