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

Abstract

Developmental changes in the coordinative organization of masticatory muscles were examined longitudinally in four children over 49 experimental sessions spanning the age range of 12-48 mo. Electromyographic (EMG) records were obtained for right and left masseter muscles, right and left temporalis muscles, and the anterior belly of the digastric. Two independent analytic processes were employed, one that relied on identification of onset and offset of muscle activation and a second that used pairwise cross-correlational techniques. The results of these two analyses, which were found to be consistent with each other, demonstrated that the basic chewing pattern of reciprocally activated antagonistic muscle groups is established by 12 mo of age. Nevertheless, chewing efficiency appears to be improved through a variety of changes in the chewing pattern throughout early development. Coupling of activity among the jaw elevator muscles was shown to strengthen with maturation, and the synchrony of onset and offset of these muscles also increased. Coactivation of antagonistic muscles decreased significantly with development. This decrease in antagonistic coactivation and increase in synchrony among jaw elevators, and a parallel decrease in EMG burst duration, were taken as evidence of increased chewing efficiency. No significant differences in the frequency of chewing were found across the ages studied. Additional considerations include the appropriateness of this coordinative infrastructure for other developing oromotor skills, such as speech production. It is suggested that the relatively fixed coordinative framework for chewing exhibited by these children would not be suitable for adaptation to speech movements, which have been shown to rely on a much more variable and adjustable coordinative organization.

Relative Kinematics of the Rib Cage and Abdomen During Speech and Nonspeech Behaviors of 15-Month-Old Children

“…The appearance of new kinematic patterns for speech breathing parallels the conclusions reached in prior electromyographic findings regarding development of speech motor control of the mandible (Moore & Ruark, 1996) and lips . In those studies toddlers exhibited coordinative patterns that, in comparison to all behaviors studied, were most like adult patterns, bearing little resemblance to those of earlier emerging behaviors (e.g., chewing; Green et al, 1997). The essence of this hypothesis is that the demands of speech production are unique among the capabilities of the developing child, such that incorporation or modification of extant patterns is not the most efficient or effective route for development of speech breathing.…”

Expression of Group I and II Metabotropic Glutamate Receptors in Trigeminal Neurons during Postnatal Development

“…Behavioral studies have demonstrated that patterns of jaw muscle activity change, in accordance with nutrient intake, during early postnatal development in rats [Westneat and Hall, 1992], dogs [Iinuma et al, 1991], pigs [Herring and Wineski, 1986], hamsters [Lakars and Herring, 1980], and humans [Green et al, 1997]. In order to understand changes in central circuitry that underlie the changes in motor output, we are conducting a series of experiments to illustrate the temporal and spatial expression of glutamate receptors in Mo5, Me5, Su5, and I5 neurons during early postnatal development.…”

The Sequential Development of Jaw and Lip Control for Speech

“…These conditions are particularly relevant to the developing oromotor system as the different articulators (a) are predominantly mediated by distinct neural centers (Barlow & Farley, 1989;Kennedy & Kuehn, 1989), (b) have unique biomechanic properties (Abbs, 1973;Ostry, Vatikiotis-Bateson, & Gribble, 1997), and (c) experience different degrees of activity and use in early ontogeny depending on their actions during sucking, chewing, vocalizing, and breathing (Bosma, 1985;Green et al, 1997;Moore & Ruark, 1996). In fact, the extent of functional partitioning within the neural centers controlling the articulators, especially in brainstem nuclei, underscores the distinctive ontogenetic and phylogenetic roles for these structures.…”