Fluid mechanical transduction mechanisms of the semicircular canal will be investigated via local mechanical stimulation using small bubbles of magnetic fluid inside the receptor. Afferent response dynamics will be characterized with linear system theory to moving magnetic fluid stimuli positioned at specific locations inside the receptor. Hypotheses of fluid mechanical transduction will be tested by comparing the afferent responses to local magnetic fluid stimuli with those resulting from physiological rotational acceleration. Guitarfish vertical and horizontal canal ampullae will be used. Their morphological size differences will enable the correlation of any experimental differences in cupular transduction mechanisms among the canals with size differences. Isolated labyrinths without a functioning efferent system will be used in the first project. Chronic, in vivo guitarfish, with functioning efferent systems will be used in the second project. The long-term objective is to determine whether fluid mechanical mechanisms can account for the diverse afferent response dynamics occurring in this receptor. A health-related objective is to determine the significance of normal versus elevated (hydrops) fluid pressures in the labyrinth as a possible mechanism for Meniere's syndrome.
