Alberta Innovates- Health Solutions

The thunder of a diesel truck rumbling down a city street. A sharp blast from a passing car's horn. The squeak and clang of a newspaper box being opened and closed. How do these and other everyday noises affect our hearing?

University of Calgary Heritage student Pam Valentine is helping to unravel the mystery of how sound is interpreted by the brain. The focus of her research is noise trauma. "Compared to the visual system we don't know enough about how the auditory system functions. We know most about how the ear and its peripheral structures work, but not a lot about how the auditory cortex of the brain processes sound," she notes.

The auditory cortex is the part of the brain located in the temporal lobe involved in hearing. Hearing involves two steps: Sound is first captured by the outer ear. It passes through the mechanical workings of the middle and inner ear to the auditory nerve that sends information derived from sound to the brain. The brain processes it in a way that Ms. Valentine and other researchers are still trying to explain.

How does the brain translate sound into information we can understand? One cue which appears to be important to the perception of sound is frequency how much of a high or low frequency there is in a sound. Researchers have discovered that a sound which is made up of a particular range of frequencies will activate neurons in a particular area of the auditory cortex of the brain.

Under the guidance of her supervisor, Heritage researcher Dr. Jos Eggermont, Ms. Valentine conducts experiments using a range of sounds from simple, one-frequency sounds to the complex, multi-frequency sounds that make up speech. Animal test subjects are put through a series of hearing tests. When a sound is played repeatedly for them, the action causes a change in brain function. "We are interested in perturbing the system in some way that allows us to better understand how the auditory system functions," Ms. Valentine explains.

"One of the ways we do this is to study noise trauma hearing loss as a result of exposure to loud sound. We want to know what happens when you experience a particular hearing loss. What are the changes in the auditory cortex? Does the part affected by the hearing loss function differently from the parts that are unaffected?"

The information Ms. Valentine is gathering could have an immediate application for patients who have experienced a hearing loss. "By looking at some of the methods of changing the brain system and understanding how it is able to adapt and function under that change, there is potential for improved treatments for hearing loss," she says. "For instance, if you want to build a better cochlear implant or hearing aid, you first have to understand what information the auditory cortex pulls out of a sound that has some meaning to us."

Pamela Anne Valentine is an AHFMR student. She works with Heritage Scientist Dr. Jos Eggermont in the Department of Psychology in the Faculty of Social Sciences at the University of Calgary. She is one of the first recipients of the 1998 Neuroscience Canada Foundation student awards for excellence in brain research. Ms. Valentine receives additional support from the Natural Sciences and Engineering Research Council of Canada.