| Citation | Although much is known of the functioning of the inner ear in lower vertebrates, the mammalian cochlea differs in possessing an electromechanical amplifier that greatly increases the selectivity and sensitivity of hearing. Ashmore has made a unique contribution to understanding this central problem of sensory physiology. He demonstrated a novel high speed motility in one specialized class of cochlear sensory cells - the outer hair cells - which operates at audio frequencies, does not use ATP, and is both controlled and energized by the electrical field in the cell's membrane. This is quite unlike conventional cellular motors such as those of the actin-myosin type. Ashmore applied for the first time the patch clamp techniques developed to study membrane properties, to the mechanism of the outer hair cell motor. With M. Holley he has identified two special protein matrices in the outer hair cell membrane; one constitutes the motor which both senses the electrical field and converts it into a constrictive force, while the other forms a cytoskeletal spring that restores the cell's shape when the motor ceases.
In addition to this seminal work, he has elucidated the ionic channels that maintain the resting potential in outer hair cells and has investigated the mechanism by which the efferent synapse on the outer hair cell acts to inhibit the cellular motor. |