Hair Bundle Movement
How does a hair bundle move when stimulated in situ? How does the tectorial membrane shape this motion?
In situ, outer hair cell bundles are embedded into a tectorial membrane while inner hair cell bundles remain free standing, though in a confined space under the tectorial membrane. Movement of the basilar membrane exerts force onto the hair bundles that to date is considered a sheering force; however, recent data questions this long-standing theorem. Mammalian cochlear hair bundles show a lack of coherence, that allow them to splay when stimulated. In addition, the shape of the hair bundles suggest that shearing would not provide stimulation in the most sensitive stereocilia direction. We are using high speed imaging (up to 100k Hz) coupled with high speed stimulation of the cochlea in situ to directly measure hair bundle motion.