Parametric Study of Single Motor Unit Waveforms in Upper Articulatory Musculature

Waveforms of single motor units were investigated, primarily in four muscles; the genioglossus, geniohyoid, mylohyoid, and anterior belly of the digastric. Units were sampled at various depths up to 25 mm from concentric bipolar electrodes inserted vertically into the tongue from points inferior to the mandible and near the midline. Units were predominantly of the usual triphasic form although many other types of waveform were observed. Most triphasic potential durations ranged from 5–7 msec, as compared, for example, with 2.5–4 msec from the same muscles with bipolar hooked wire electrodes. Variables determining these waveforms, and differences in waveforms and unit amplitudes from muscle to muscle will be discussed. [This work was supported by grants from the National Science Foundation.]