Tinnitus or “ringing in the ears” is an often unbearable condition that affects more than 50 million Americans. It refers to the perception of sound when no external sound is present. Tinnitus has long been associated with hearing damage (e.g., overexposure to loud sound); but in recent years, scientists have hypothesized that loss of neuronal activity, from either auditory or non-auditory centers, can result in a re-adjustment in the brain circuits that mediate hearing. When nerve cells in the brain not receive adequate sensory input, they may compensate by amplifying all incoming signals. In some situations, this readjustment may lead to the perception of sounds when no sounds are present. Learn more about tinnitus and view videos from the Lauer Tinnitus Research Center’s seminar »
In almost all cases, tinnitus is a subjective noise, meaning that only the person who has tinnitus can hear it. People describe hearing different sounds: ringing, hissing, static, crickets, screeching, whooshing, roaring, pulsing, ocean waves, buzzing, dial tones, even music.
In general, there are three ways to describe a patient’s personal perception of the tinnitus sound:
Tonal Tinnitus: The perception of near-continuous sound (or overlapping sounds) with well-defined frequencies. The perceived volume of the tinnitus often fluctuates. Tonal tinnitus is generally associated with subjective tinnitus.
Pulsatile Tinnitus: The perception of pulsing sounds, often in-beat with the patient’s heartbeat. Pulsatile tinnitus is often associated with objective and somatic tinnitus.
Musical Tinnitus: The perception of music or singing, sometimes the same tune on a constant loop. Also known as Musical Ear Syndrome, Musical Tinnitus is very rare.
There is some scientific evidence that a patient’s tonal perception of tinnitus is influenced by the etiology (the underlying cause) of their tinnitus. However, current science has not identified a definitive correlation.
Lauer Tinnitus Research Center
In partnership with the Lauer family, Massachusetts Eye and Ear launched the Lauer Tinnitus Research Center in 2015 with the goal of advancing research to better understand and treat the debilitating condition of tinnitus. The Blakeley Foundation provides support to a new laboratory run by Daniel Polley in Boston.
Led by M. Charles Liberman, PhD, Stéphane Maison, PhD, MS, Daniel Polley, PhD, Konstantina Stankovic, MD, PhD, and Anne Takesian, PhD, the Research Center brings together years of experience and state-of-the-art research techniques to bear on the problem of tinnitus.
The following strategies are underway to study tinnitus in the ear and the brain:
Cochlear Nerve Repair and Tinnitus – Dr. Charlie Liberman, along with his colleague Dr. Sharon Kujawa, discovered in 2009 that even brief exposure to loud noise can result in permanent loss of auditory nerve fibers. They named this condition “hidden hearing loss,” because it does not affect the audiogram or appear in routine histological preparations of the cochlea. However, the loss of communication between the inner ear and cochlear nerve may be a root cause for difficulties understanding speech in noisy environments and may be a key link in the chain of events that causes tinnitus. Dr. Liberman and his colleagues are working on therapeutic approaches to regrow these sensory neurons in mouse models in hopes of restoring hearing function and alleviating tinnitus.
Imaging the Inner Ear in Tinnitus – Dr. Konstantina Stankovic is pioneering the development of a new technology to non-invasively image the tiny sensory cells of the human inner ear. Because the inner ear is encased in the hardest bone in the body, no current imaging techniques can “see” the cells and neurons of the ear. Her research aims to develop an endoscope to be used in the exam room to assess neuronal survival in the inner ear, a key to diagnosing the cause of tinnitus.
Tinnitus in the Brain – Dr. Dan Polley is a leading expert in the physiology and plasticity of auditory processing areas of the brain. He is using cutting edge technologies for chronic imaging at a cellular scale to assess changes in the patterns of neural activity that represent the underlying signature of tinnitus in mouse models. His work is also investigating new strategies for direct brain stimulation that might reverse pathological patterns of activity and restore more normal sound perception.
Dr. Anne Takesian has recently joined this interdisciplinary tour de force to understand the neural basis of tinnitus. Her laboratory uses advanced techniques in neuroscience to map the genetic, cellular, and synaptic changes within the central auditory system that may underlie tinnitus. She is also working to identify therapies for tinnitus that leverage the brain’s inherent ability to restructure by tapping into precise cellular mechanisms that promote plasticity.
Testing Tinnitus Strategies in Humans – Dr. Dan Polley will be investigating new approaches to turn down the subjective intensity of tinnitus and restore more normal abilities to follow conversations in noisy environments. Using a customized auditory training software interface, Dr. Polley and his team have been successful in boosting speech recognition abilities in persons with hearing loss and now wish to apply this technology to tinnitus. Dr. Polley will be combining electrophysiological testing with his new approach for "brain training" to identify physiological changes in brain processing that accompany improvements in speech recognition and tinnitus severity.
Dr. Liberman and Dr. Stéphane Maison will be following up on their 2016 study that identified a physiological signature for a “hidden hearing loss” that cannot be detected with conventional audiological tests but underlies difficulties tracking speech in noisy environments. Liberman and Maison will develop and refine their battery of tests to identify objective physiologic measures of aberrant neural processing that “hides” behind normal audiograms but may provide important clues about the mechanisms and manifestations of tinnitus.
The Lauer Tinnitus Research Center will undoubtedly drive the field forward in developing scientifically proven treatments to alleviate tinnitus.