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Ian Russell and his colleagues are interested in examining how outer hair cells interact with other cochlea elements so that feedback is delivered with optimal gain, time during each cycle, and place on the basilar membrane, to amplify and shape the cochlea’s responses. They will investigate the relative significance of outer hair cell somatic motility and hair bundle motility as sources of cochlear amplification. The production by Guy Richardson’s group of transgenenic mice with detached tectorial membranes offers us novel ways to investigate the role of this important extracellular matrix in cochlear sensory processing. They will investigate the cellular basis of the compression of cochlear responses and how efferent neural control and mutual interaction between outer hair cells and other elements of the cochlear partition regulate cochlear sensitivity. In vivo and in vitro preparations will be used to answer these questions through a combination of micromechanical, electrophysiological, and modelling techniques on normal preparations and on those in which the cochlea’s principal components have been modified through genetic manipulation.

In a further collaborative study with Guy Richardson, Ian Russell and his group will investigate the dependence of hair cell mechanosensitivity on the transfer of mechanical energy from the hair bundle to the transducer conductance. Cochlear sensitivity depends on energy transfer between the tectorial membrane and the outer hair cell hair bundles and, crucially, on the setting of the transducer conductance operating point. They will use a novel interferometer, cochlear preparations and transgenic mice with deletions of cochlear specific proteins to address the following questions: 1) How do inter stereocilia links contribute to hair bundle mechanics 2) How do the mechanical properties of outer hair cell hair bundles and the tectorial membrane determine the way these structures interact at acoustic frequencies? 3) Do outer hair cells actively regulate the operating point of the transducer conductance and hence cochlear sensitivity?

In collaboration with Professors Manfred Kössl and Marianne Vater, Ian Russell is investigating the peripheral mechanisms and development of the extraordinary sharp tuning of the acoustic fovea in the moustached bat cochlea and the development of echolocation behaviour and the peripheral and central processing of echolocation signals.

In collaboration with Dr Elizabeth Glowatzki and Professor Paul Fuchs we are investigating the development of afferent neurones, and their functional relationship to inner and outer hair cells in the spiral ganglion of the rat cochlea using a unique slice preparation of the cochlea. Our aim is to see how these neurones make and break synaptic connections during development and to recorded responses from afferent fibres that innervate outer hair cells.