Symmetry of Mandibular Muscle Activity as an Index of Coordinative Strategy

Abstract

Electromyographic activity of bilateral mandibular muscle pairs in humans was studied during several tasks: mastication, voluntary oscillation of the jaw, and speech production, as a replication and extension of an earlier investigation by Moore, Smith, and Ringel (1988). The synchrony of activity within and across these paired muscles (masseter, medial pterygoid, and the anterior belly of the digastric) was evaluated by statistical comparison of zero-lag cross-correlation coefficients between all possible pairs. Paired comparisons were classified and combined according to anatomical and biomechanical properties into comparisons of homologous pairs (e.g., synchrony of activity in right masseter with left masseter), ipsilateral synergists (e.g., right masseter with right medial pterygoid), contralateral synergists (e.g., right masseter with left medial pterygoid), ipsilateral antagonists (e.g., right masseter with right digastric), and contralateral antagonists (e.g., right masseter with left digastric). Statistical comparison of the coactivation within muscle groups (across tasks) and across these muscle groups (within tasks) revealed significantly different groups of coactivated groups for each of the three tasks studied. The grouping of these muscles into coactivated groups always included homologous pairs among those most synchronously active. During mastication, homologous pairs and ipsilateral synergists were coactivated to a degree significantly greater than either of the antagonistic groups or the contralateral synergists. During voluntary oscillation of the jaw, coactive muscle groups were shown to be primarily the homologous pairs; synergists were coactivated to a significantly lesser degree, and antagonistic muscles were reciprocally active. During speech production, only homologous pairs emerged as a highly coactive group, although synergists and antagonistic pairs were coactive to a lesser degree. This finding was interpreted as a further indication of the coordinative plasticity among mandibular muscles, and as a demonstration of the vast differences in the apparent coordinative strategies for speech and nonspeech tasks. Speculation regarding the root of these differences is focused on the differences in kinematic and force-generating requirements of each task. Keywords jaw; electromyography; speech; chewing; human Like other motor behaviors, motor control of orofacial movement can be modulated by a variety of neural mechanisms, including brain stem and cortical influences, which may vary in relative importance across and perhaps within behaviors. Of critical importance to our understanding of speech production is the relationship of speech motor control mechanisms and neural pathways to those of other orofacial motor behaviors. Some of the best understood mechanisms include those associated with rhythmic behaviors such as NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript mastication, which has been shown to be controlled by a brain stem central pattern generator (CP...

Kinematics of the quadrate bone during feeding in mallard ducks

“…Cross correlation is a signal processing technique that has been used in a variety of fields, including kinematics (Green et al, 2000;Bishop, 2006), electromyography studies (Moore, 1993;Wren et al, 2006) and neurobiology (Shao and Tsau, 1996). From each trial we chose 10 consecutive cycles of feeding to analyze based on the regularity of the movement, i.e.…”

Development of Chewing in Children From 12 to 48 Months: Longitudinal Study of EMG Patterns

“…Despite large intersubject variability (Ahlgren 1966;Dellow and Lund 1971;Møller 1966), a consistent pattern of muscle activation for chewing has emerged. Most prominent in the chewing cycle is the rigid, reciprocal pattern of alternating activity between antagonist muscles (e.g., anterior digastric with masseter) (Ahlgren 1966;Møller 1966;Moore 1993;Moore et al 1988;Vitti and Basmajian 1977). During the opening phase of mastication the jaw depressors are active, and activity in the jaw elevators is inhibited (Møller 1966;Vitti and Basmajian 1975), yielding a relatively rapid jaw opening phase (Josell et al 1984).…”

“…Ipsilateral synergistic pairs (e.g., right masseter and right temporalis) are similarly coactive during chewing (Ahlgren 1966;Møller 1966;Moore 1993;Vitti and Basmajian 1977). Several studies have described asymmetric activity in contra-lateral synergists (e.g., right masseter and left temporalis) (Luschei and Goldberg 1981;Møller 1966;Moore 1993). Luschei and Goldberg (1981) reported, for example, that activity in the working-side temporalis begins earlier than that of the balancing-side masseter.…”

“…A large number of descriptive studies has sought to quantify muscle activation patterns characteristic of chewing by humans (Ahlgren 1966;Alvarado Larrinaga et al 1989;Garrett and Kapur 1986;Horio and Kawamura 1989;Josell et al 1984;Luschei and Goldberg 1981;McCarroll et al 1989;Møller 1966;Moore 1993;Moore et al 1988;Schwartz et al 1984;Steiner et al 1974;Basmajian 1975, 1977). Despite large intersubject variability (Ahlgren 1966;Dellow and Lund 1971;Møller 1966), a consistent pattern of muscle activation for chewing has emerged.…”

“…Homologous muscle pairs (e.g., right and left masseter) are generally coactivated (Ahlgren 1966;Møller 1966;Moore 1993;Vitti and Basmajian 1977), although levels of activation within these pairs are unequal, with the working side exhibiting greater activity (Ahlgren 1966;Vitti and Basmajian 1975). Ipsilateral synergistic pairs (e.g., right masseter and right temporalis) are similarly coactive during chewing (Ahlgren 1966;Møller 1966;Moore 1993;Vitti and Basmajian 1977). Several studies have described asymmetric activity in contra-lateral synergists (e.g., right masseter and left temporalis) (Luschei and Goldberg 1981;Møller 1966;Moore 1993).…”