Coordination of mandibular muscle activity in infants with Down syndrome during feeding

Normally developing infants produce adult-like mandibular muscle activity during chewing by 12 months of age. However, infants and children with Down syndrome may exhibit delays in obtaining the typical mandibular motor patterns for feeding. Some reports have hypothesized that these patterns may even be deviant. Little quantitative data exists regarding the development of mandibular muscle activity in infants and children with Down syndrome.

The present EMG study describes the coordinative muscle patterns of infants with Down syndrome during feeding. This investigation allowed a comparison of the feeding patterns of infants with Down syndrome with normally developing infants. The crosscorrelation analysis yielded to points of interest: the peak correlation coefficient and the lag to the peak. A low to moderate degree of coupling was noted for the homologous and synergistic muscle pairs as well as relatively weaker coupling for the antagonistic muscle pairs during feeding. Mean absolute lag values demonstrated longer lags for the antagonistic muscle pairs and shorter lags for the homologous and synergistic muscle pairs.

Findings of this study suggest a nonlinear relationship between age and development of feeding skills. A linear relationship between gross motor feeding development, however, may be evident. Thus, feeding difficulties may stem from a developmental delay versus a distinct, deviant developmental pattern. The timing of muscle activity was found to be similar to the masticatory patterns of typically developing infants.