Intramural mechanics of the human tongue in association with physiological deformations

Contraction of the tongue musculature during speech and swallowing is associated with characteristic patterns of tissue deformation. In order to quantify local deformation (strain) in the human tongue, we used a non-invasive NMR tagging technique that represents tissue as discrete deforming elements. Subjects were studied with a fast gradient echo pulse sequence (TR/TE 2.3/0.8 ms, slice thickness 10 mm, and effective spatial resolution 1.3×1.3 mm). Individual elements were defined by selectively supersaturating bands of magnetic spins in resting tongue tissue along the antero–posterior and superior–inferior directions of the mid-sagittal plane, resulting in a rectilinear square grid. Axial and shear strains relative to the rest condition were determined for each element and represented by two-dimensional surface strain maps. During forward protrusion, the anterior tongue underwent positive antero–posterior strain (elongation) (maximum 200%) and symmetrical negative medial–lateral and superior–inferior strain (contraction). During sagittal curl directed to the hard palate, the tongue exhibited positive asymmetrical antero–posterior strain (maximum 160%) that increased radially as a function of distance from the center of curvature (r=0.9216, p<0.0005), and commensurate negative strain in the medial–lateral direction. Similarly, the magnitude of anterior–posterior strain during left-directed tongue curl was proportional to the distance from the curved inner surface (r=0.8978, p<0.0005). We conclude that the regulation of tongue position for the motions studied was related to regional activation of the intrinsic lingual musculature.