Master of Science (MS)
Age-related declines in vestibular function affect balance and coordination in older adults. Of perhaps equal importance, but less understood, are the potential implications of vestibular degeneration on cardiovascular homeostasis. Recent evidence suggests that the semi-circular canals, a section of the vestibular system, may be involved in the vestibulosympathetic reflex (VSR), but the extent to which the aging of the semi-circular canals interferes with cardiovascular homeostasis is unknown. Activation of the intact VSR results in increases in tonometric blood pressure (TBP) and heart rate (HR) as well as decreases in cardiac output (Q) and pre-ejection period (PEP). The purpose of this investigation was to observe reflexive changes in the VSR and cardiovascular function during activation of the horizontal semi-circular canals using bithermal binaural caloric irrigation in young (n =11; 18-39), middle-aged (n = 7; 40-64), and old (n = 9; 65+) adults and to describe age-related changes in cardiac dynamics in order to identify a possible indicator of disease and/or disease risk. 3x2 repeated measures ANOVAs revealed significant increases in slow-phase velocity for all subjects under all conditions, which indicate adequate excitation of the semi-circular canals to stimulate the VSR; TBP increased in the young and middle-aged groups to a greater degree than the old group; RR-intervals tended to decrease in young adults while either decreasing to a much lesser extent or increasing in the middle-aged and old groups. A decrease in RR-intervals indicates an increase in heart rate, and, thus activation of the VSR. Similarly, sympathovagal balance consistently increased in young participants but not in the old adults. These preliminary results cannot confirm an age-related deterioration in semi-circular canal control of cardiovascular function; however, they are sufficient to underscore the importance of the continued investigation of age-related changes in the VSR.
Document Availability at the Time of Submission
Release the entire work immediately for access worldwide.
deVeer, Melissa J., "Hemodynamic and ocular responses to caloric stimulation and age-related disparities" (2005). LSU Master's Theses. 3174.
Robert H. Wood