Temporal properties of electromyographic patterns in children’s and adults’ speech

Abstract

Electromyographic patterns of children’s and adults’ speech production were analyzed to examine temporal relationships among pairs of muscles commonly viewed as functioning either as ‘‘agonists’’ or ‘‘antagonists.’’ It was hypothesized that adults’ greater degree of speech motor control would be evidenced by stronger positive correlations between agonist muscle pairs (e.g., obicularis oris inferior and obicularis oris superior or anterior belly of digastric and depressor labii inferior). In addition, it was expected that greater negative correlations would occur for adults between antagonist pairs (e.g., obicularis oris inferior and depressor labii inferior). A group of adults and three groups of children (5-, 8-, and 11-years old; eight subjects/group) produced multiple repetitions of the phrase, ‘‘Say pap again.’’ EMG activity was measured relative to the two labial consonants in the acoustic waveform, and cross correlations were computed between various muscle pairs. In general, the predicted results were obtained, although negative correlations between antagonist pairs often were not observed. Significant, age-related differences occurred primarily between the adults and the 5-years old, and occasionally between the adults and the 8-years old. The findings suggest that adults tend to have more discrete separation between agonist and antagonist muscle groups in speech production than young children.