A RADIAL GRADIENT OF FIBRIL DENSITY IN THE GERBIL TECTORIAL MEMBRANE

The tectorial membrane plays a key role in the transduction of mechani cal to neural energy in the inner ear. To better understand the transd uction process the composition of the tectorial membrane needs to be e lucidated. This study was done to determine if Type A collagen fibrils are distributed homogeneously in the tectorial membrane or if there a re longitudinal or radial gradients of fibril concentrations. Our resu lts suggest that while there is no longitudinal gradient, there is a r adial gradient of fibril concentration, The concentration of fibrils i n the limbal (inner) zone of the tectorial membrane exceeds that in th e marginal (outer) zone in all cochlear locations examined. This gradi ent is most marked in the basal, high frequency coding region of the c ochlea. While fibril gradients in the tectorial membrane have not been the focus of previous investigations, several findings by other autho rs support the proposition that the marginal zone of the tectorial mem brane is more compliant than the limbal zone. This radial gradient of tectorial membrane stiffness is likely to contribute to the characteri stics of movement of the cochlear partition.