Sip-sizing behaviors in natural drinking conditions compared to instructed experimental conditions.

To understand disordered physiology, it is first necessary to determine what constitutes normal function. Liquid sip size during swallowing in healthy individuals has been investigated with varied results. Bolus size is a variable that is manipulated in both research studies and clinical swallowing assessments, so defining normal sip size has relevance in both domains. This study looked at sip size under instruction in experimental tasks and compared it to sip size in free drinking while participants were unaware that drinking was being observed. A statistically significant difference was found in water sip volume between natural drinking (mean = 16 ml) and instructed experimental drinking tasks (mean = 6.6-6.8 ml). This difference far exceeded the magnitude of sip-size variation observed between instructed drinking tasks using different stimuli and as a function of participant's gender or age group.

Tongue control for speech and swallowing in healthy younger and older subjects.

Current literature on oral motor control reports contradictory findings regarding physiological, functional and sensory changes that occur in the muscles of the tongue with normal aging. It has been suggested that the high level of activity required of tongue muscles in mastication and speech may play a role in preserving them when other skeletal muscles are more likely to show functional effects of such changes. To test whether indeed tongue movements remain unaltered in both speech and swallowing tasks as a function of aging, kinematic measures of tongue dorsum movements were taken as 21 healthy young (20-30) and older (65-74) adults performed repeated iterations of speech tasks and a sequential water swallowing task. Tongue motion was recorded using electromagnetic articulography and from these data information was extracted with respect to movement range, duration, and variability. The findings suggest that in general tongue movements for swallowing were slower and more variable than for speech, and most importantly, more variable among older than younger participants. As well, the findings show that aging does influence the nature of tongue motions, in particular by inducing a more extreme distinction in the variability of movements for speech (less variable) and swallowing (more variable) tasks.