Kavli Institute For Theoretical Physics
The KITP Public Lecture Series

How Hearing Happens

sponsored by Friends of KITP

As the gateway to human communication, the sense of hearing is of enormous importance in our lives. Hearing commences with the capture of sound energy by hair cells, the ear's sensory receptors, which then convert that energy into electrical signals that the brain can interpret. But the hair cell is not a passive recipient of stimuli; rather it uses an active process to enhance its mechanical inputs, amplifying them by as much as a thousandfold. If the active process deteriorates, we grow less sensitive to subtle differences in frequency and therefore suffer a diminished ability to discriminate sound sources. The active process is highly nonlinear, making the ear sensitive to sounds over a trillion-fold range in power. By enhancing weak stimuli and suppressing strong ones, this feature allows us to enjoy a soloist as comfortably as a full orchestra hundreds of times as loud. The active process can also become unstable — in a very quiet environment most normal ears spontaneously emit sound! I will explain how experiments on individual hair bundles have shown that the bundle's operation accounts for the above characteristics. In addition, we shall consider how hearing loss can be remediated through the cochlear implant —and how hearing might be restored by the regeneration of hair cells. 

About the Speaker

A. JAMES HUDSPETH is the F. M. Kirby Professor and Head of the Laboratory of Sensory Neuroscience at Rockefeller University. Originally hailing from Texas, he received his PhD from Harvard in 1973 and his MD from Harvard Medical School in 1974. Following a year’s postdoctoral training at the Karolinska Hospital in Stockholm, he held a succession of faculty positions at Caltech, UCSF, and the UT Southwestern Medical Center in Dallas. He was named a Howard Hughes Medical Investigator in 1993 and moved to Rockefeller two years later. Among this many honors, Dr. Hudspeth is a member of the National Academy of Sciences and the American Academy of Arts and Sciences. His research focuses on hair cells, the sensory receptors of the internal ear. Hair cells are of interest both because of our limited understanding of their operation and because their degeneration underlies hearing impairment in 30 million Americans.