March 25, 1994
Media Contact: John Welby
Phone: (410) 955-1078
WHERE SOUND COMES FROM
We hear a gunshot. Almost instantly we are able to determine the source of the sound. This apparently simple response is actually the result of a series of complex computations carried out by the brain, computations that would be impossible without the two highly visible flaps of cartilage we call ears.
Eric D. Young, Ph.D., professor of biomedical engineering, of neuroscience and of otolaryngology -- head and neck surgery at Johns Hopkins, has shown that our ability to locate sound, a completely different process from our ability to hear, is highly dependent on the external ear. Young says the shape of our ears, the distance of our ears from the sound source, and the distance between our two ears all play a part in the process. He says that understanding this process will help researchers help many of the 28 million Americans suffering from hearing loss.
For more information, call John Welby (410-955-1078).
CLOSE YOUR EYES, MISS THE ANSWER
You've lost function in one ear. Your doctor says an inner ear infection caused the problem, yet you are unsteady. You feel dizzy and nauseated. Should you lie down, close your eyes and wait it out? Not according to David Zee, M.D., professor of neurology at Johns Hopkins. 'We should do exactly the opposite," he says. "This is precisely when we need stimulation both from our eyes and our feet. Our brain needs the experience of trying to walk and focus our eyes so it can begin the process of recovery."
According to Zee, our vestibular, or balance system, modifies signals sent to the brain based on the information it receives from the environment. This means that when the balance system is damaged, it can learn to compensate by trying to move and look around. This compensatory ability lets the vestibular system develop coping strategies and eventually rehabilitate itself. Zee is studying how rehabilitation occurs in order to design new programs of therapy to hasten recovery.
For more information, call John Welby 410-955-1078
YOU'RE DIZZY? SEE A PSYCHIATRIST
Dizziness,, or vertigo, is one of the most frequent reasons people visit the doctor -- the ninth most common, in a recent study of outpatients. Yet most patients with vertigo leave the doctor's office disappointed, even after repeat visits. In addition, they frustrate physicians and tax the health system studies show, because vertigo is so difficult to treat. Why? "Because there's often no clear-cut medical reason for the problem" says Hopkins psychiatrist Michael Clark, M.D., M.P.H. 'Vertigo," he says, "often stems from a psychiatric condition." Sufferers have a high rate of major depression, panic disorder or other mental problems, says Clark. He's one of few psychiatrists specializing in vertigo and is developing methods for physicians to spot patients whose dizziness is a psychiatric problem.
For more information, call Joann Rodgers at 410-955-8725.
TO ADAPT JUST CLOSE THE CAP
You cock your head, and immediately impulses from the eyes and inner ear notify your brain. Yet after the brain takes in this info-bit, it no longer needs to be told that your head is tilted. This ability of the nervous system to damp down or stop sending messages about a particular sensory event called adaptation -- keeps human and animal brains from being swamped with information.
Hopkins neuroscientist Peter Gillespie, Ph.D., says this process is amazingly mechanical. Tufts of tiny hairlike cells within the ear contain, at their tips, the biological equivalent of bottle caps. When gravity or other forces push the hairs over like so many tin soldiers, the "caps" pop open, allowing an incredibly fast flow of current to enter the cells. This starts the message to the brain about the new position. Working with frogs, Gillespie also has found a system that appears to ease the cap shut. For more information, call Joann Rodgers at 410-955-8725.
SINGING EARS AND DANCING HAIR CELLS
Within the last 20 years, scientists have learned that the auditory hair cells of the inner ear translate the sound in the world around us into a language the brain can understand. But that's not all. According to William Brownell, Ph.D., professor of otolaryngology - head and neck surgery at Johns Hopkins, they also sing and dance.
Says Brownell: "Hair cells move in response to sound and, in turn, create a sound of their own." Brownell says that understanding this process, called electromotility, will help scientists to unravel the mysteries of how these highly specialized cells enhance our ability to hear.
For more information, call John Welby at 410-955-1078.