15th International Congress of Phonetic Sciences (ICPhS-15)
This study describes the neuromuscular organization of the superior longitudinal muscle (SL) of the human tongue with focus on whether SL organization is compatible with multiple strategies of motor unit (MU) activation. Microdissection demonstrates that the human SL is comprised of discrete muscle fascicles (8.5-16 mm length) that occupy <20% of total SL length. Immunohistochemical staining of myosin heavy chain (MyHC) isoforms demonstrates the presence of at least three different MyHC phenotypes in the human SL: fibers composed of slow but not fast MyHC isoforms, fibers composed of fast but not slow MyHC isoforms, and hybrid fibers composed of both slow and fast MyHC isoforms. These data are compatible with differential organization of SL motor units according to antero-posterior tongue location and muscle fiber MyHC composition. Whether two strategies are in operation in SL activation, one in which MUs are selected by virtue of location and another in which MUs are selected by virtue of fiber MyHC identity (and related properties) awaits physiological investigation.
Bibliographic reference. Sokoloff, Alan J. (2003): "Neuromuscular strategies for human tongue movement", In ICPhS-15, 3181-3184.