Irving said: "When we switch on a bright light our eyes detect the increase in light levels and the brain sends a message to the eye to tell it to contract the pupil and let in less light. This is a feedback system where the brain is getting information from the eye about its surroundings, processing that information, and sending messages back to the eye to help it cope with different situations. We think something very similar is happening with the ear in spatial hearing."
"The brain is constantly monitoring the sounds around us and so knows what normal sound levels it would expect. When we introduce an earplug, it can detect the reduction in sound being received and we think it is actively sending messages back to the ear telling it how to cope with the new hearing loss, perhaps by stimulating or increasing the signal which is being blocked. It's compensating for the problem in a really clever way."
Irving is trying to locate the place in the brain which is channeling these feedback messages back to the ear.
"We already have a likely candidate called the OCB, the Olivocochlear Bundle, which is a part of the brain that we know is a centre of feedback information being transmitted from the brain back to the ear. We're now trying to work out if the OCB is responsible for spatial hearing in ferrets."
The Pauline Ashley Prize will allow Irving to work with a team led by Professor Charles Liberman at the Eaton Peabody Lab at MIT/Harvard, leading experts on the OCB system. His study will compare the performance of ferrets which have had their OCB removed with normal ferrets in the "ring of sound".
At the same time, Irving is conducting a study with human subjects who have volunteered to wear an earplug for five days. These subjects will be tested in a similar ring of sound and their performance measured over time. Early results show that humans also have the same abil
Contact: David Reid
Deafness Research UK