Relative kinematics of the rib cage and abdomen during speech and nonspeech behaviors of 15-month-old children

Speech motor control emerges in the neurophysiologic context of widely dist ributed, powerful coordinative mechanisms, including those mediating respir atory function. It is unknown, however, whether developing children are abl e to exploit the capabilities of neural circuits controlling homeostasis Fo r the production of speech and voice. Speech and rest breathing were invest igated in eleven 15-month-old children using inductance plethysmography (Re spitrace). Rib cage and abdominal kinematics were studied using a time-vary ing correlational index of thoracoabdominal coupling (i.e., reflecting the synchrony of movement of the rib cage and abdomen) as well as simple classi fication of the moment-to-moment kinematic relationship of these two functi onal components (i.e., concurrent expansion or compression, or oppositional movement). Results revealed markedly different patterns of movement for re st breathing and speech breathing, although within types of vocalization (n onspeech vocalization, babbling, true word production) no differences were apparent. Whereas rest breathing was characterized by tight coupling of rib cage and abdominal movement (average correlation coefficients usually exce eded .90), speech breathing exhibited weak coupling (the correlation coeffi cient ranged widely, but averaged about .60). Furthermore, speech productio n by these toddlers included the occurrence of both rib cage and abdominal paradoxing, which are observed infrequently in adult speakers. These result s foil to support the suggestion that speech emerges From the extant coordi native organization of rest breathing. Rather, even in its earliest stages breathing for speech and voice exhibits kinematic properties distinct from those of other observed behaviors.