Discoordination of laryngeal and respiratory movements in aged rats

Voice and swallowing actions require the coordination of multiple motor systems, and this coordination may be impaired with aging. Although recent work has reported impairments in age-related laryngeal kinematics in rats, the temporal relationship of laryngeal excursions to the respiratory cycle is unknown. The goal of this study was to assess laryngeal-respiratory coordination by examining temporal interrelationships between change in laryngeal aperture and chest wall movement during quiet breathing in a rat model. Glottal images were recorded, digitized, and synchronized with respiratory signals, and temporal features were measured. In the young animals, glottal opening began before the onset of inspiration, and glottal and respiratory cycles were phasic and stereotypic. In old animals, however, inspiration often began during the glottal closing phase, and both respiratory signals were asymmetric. Discoordination of laryngeal and respiratory motor actions associated with aging may be caused by a generalized decline in sensorimotor cranial functions and may contribute to age-related swallowing and communication impairment.