Our Aging Ears and Brains: Why Listening in Background Noise Gets Tougher as We Age
Older adults often have trouble understanding what someone is saying when surrounded by background noise, such as at a restaurant or party, but their ears may not be the only problem. Researchers at the Medical University of South Carolina are studying how much the brain plays a role as well. Using magnetic resonance imaging (MRI), the researchers performed brain scans on 36 older and younger adults as they tested their ability to identify certain words, some of which had been filtered to make them difficult to understand. The researchers analyzed the scans to functionally define speech- and attention-related areas of the brain and then examined the volume of gray matter in those regions for age-related changes. They found that, in general, older adults were significantly worse at identifying words than younger adults in challenging listening conditions. Even after eliminating variation due to possible hearing loss, these differences in performance corresponded closely to a loss of volume in a small portion of the auditory cortex, a part of the brain that processes what our ears hear. What's more, the relationship between the volume of gray matter in this brain region and the ability to identify words was present in both younger and older adults, suggesting that aging may intensify developmental problems that a person may have in understanding speech. The findings could help us better understand presbycusis, a type of hearing loss brought on by aging that also involves the brain's ability to process what the ears hear.
The poster "Structural Integrity of Speech-Related Temporal Lobe Cortex Predicts Age-Related Differences in Word Recognition" (#141) takes place Sunday, February 15, at 1:00 p.m. in the Grand Ballroom.
Can a Dietary Supplement Stave Off Hearing Loss?
Many people take a vitamin each morning to maintain good nutrition, energy, bone strength, and overall health. Can popping a pill also protect our hearing against damage caused by loud noise? Researchers at the University of Michigan and the University of Florida, together with the biosciences company OtoMedicine, have demonstrated that temporary noise-induced hearing loss - the hearing loss you might feel immediately after attending a loud concert but that goes away in a day or two - can be prevented in guinea pigs by a combination of the antioxidants beta-carotene, vitamin C, and vitamin E and the mineral magnesium, when administered before exposure to a loud sound. Because repeated bouts of temporary noise-induced hearing loss may lead to permanent noise-induced hearing loss, the scientists hope to determine whether prevention of the former can stave off the latter in various animal models and in humans.
In a second study conducted with colleagues at Washington University, the researchers demonstrated that permanent noise-induced hearing loss can also be prevented in mice through the combination of the same nutrients administered before exposure to a loud noise. (They showed similar results in guinea pigs in an earlier study.) However, unlike in guinea pigs, they found that the nutrients protect a structure in the mouse's inner ear that is implicated in age-related hearing loss. They plan to test whether the nutrient supplements may be able to prevent this type of hearing loss as well. The researchers are currently conducting clinical trials of the supplements' ability to prevent noise-induced hearing loss in college students, military personnel, and factory workers in Florida, Sweden, and Spain.
The posters "Reduction in Permanent Noise-Induced Threshold Deficits in Mice Fed a Combination of Dietary Agents" (#826) and "Prevention of Temporary Noise-Induced Threshold Deficits Using Dietary Agents" (#827) take place Wednesday, February 18, at 1:00 p.m. in the Grand Ballroom.
Finding the Words: What Our Brains Tell Us about Language Disorders
We rely mightily on our brains to produce and understand language - whether we're simply naming a person or object or engaging in a lively discussion. Technologies in brain imaging - from those involving the brain's electrical activity to those measuring blood flow to regions of the brain - can tell us a lot about what's happening in the process. Dr. Allen Braun, chief of the language section in NIDCD's Division of Intramural Research, will demonstrate how a combination of imaging technologies can be used to teach us more about how the brain produces and comprehends language, both in people with normal skills and those with a language disorder. In addition, he'll show how language used in its most natural form - to communicate - is most effective in bringing to light the true symptoms of a language disorder. In the same workshop, an opera singer who suffered a severe stroke in 1995 will describe her experience with expressive aphasia, a condition that makes it difficult to express language. She will also perform several music selections.
The presentation "Brain Networks for Language Production and Comprehension" (#227) takes place Sunday, February 15, at 7:05 p.m. in the Harborside Ballroom A-C. The presentation "A Case Study of Expressive Aphasia in an Opera Singer" (#228) immediately follows at 7:35 p.m. in the same location.
Maintaining Balance and Listening at Same Time May Become More Difficult for Older Adults
Listening to a conversation or audio book while walking or exercising sounds simple enough for most people, but it may become more difficult for people in their upper 70s and above, according to new research from the University of Pittsburgh Medical Center. Researchers evaluated how well three groups of adults -- healthy young (ages 24-27), old (ages 65-71), and "old-old" (ages 76-82 years) -- were able to conduct a listening exercise while their visual and balance systems were kept busy. Seated in swivel chairs that were either upright or at a 30-degree tilt, the volunteers performed two listening-related tasks while motionless or spinning in darkness or in light. In one task, they listened to a high- or low-pitch tone and pressed a button in their right or left hand depending on the pitch. In the second task, volunteers listened to tones in their right or left ears and pressed the corresponding button. The researchers found that, in general, all age groups reacted more slowly to the audio cues when spinning than when motionless. However, this was especially true for people in the oldest age group. They also found that stimulation of the ear's gravity-sensing organs - through the 30-degree tilt of the chair -- was especially powerful in slowing down a person's auditory reaction time. Again, this effect was most pronounced for people in the oldest age group. The National Institute on Aging also supported this research.
The poster "Visual-Vestibular Stimulation Interferes with Auditory Information Processing Task Performance in Older Persons" (#961) takes place Wednesday, February 18, at 1:00 p.m. in the Grand Ballroom.
Built-in Volume Control Helps Protect Auditory Nerve Against Loud Sounds
When we hear a sound, sensory cells in our inner ear trigger the release of a chemical - called a neurotransmitter - to neighboring nerve cells, which, in turn, relay the auditory message to our brain. When our ears are exposed to very loud sounds, such as the blast of a firecracker, too much of the neurotransmitter is released, damaging these auditory nerve cells and causing hearing loss. NIDCD-funded researchers at the Massachusetts Eye and Ear Infirmary, Harvard Medical School, have found that auditory nerve cells temporarily reduce the expression of a key neurotransmitter receptor on their surfaces when exposed to loud noise, and they wanted to know why. In a new study on mice, the researchers used a drug to block the ability of the auditory nerve cells to remove the receptor and then exposed the mice to a moderately loud sound that, under normal conditions, would not damage the nerve cells. They found that the mice given the blocking drug experienced hearing loss for at least six hours following exposure to the normally harmless sound. Also, the blocker accelerated the death of auditory nerve cells that had been incubated in the lab with neurotransmitter chemicals that are normally released during sound stimulation. The researchers suggest that the auditory nerve regulates the expression of these surface receptors as a way to protect itself against the chemical overload caused by loud noise. Although the scientists believe that auditory nerve cells can rid their surfaces of the receptor by as much as 50 percent, this may not be enough protection against all loud sounds.
The poster "Regulated Expression of Surface AMPA Receptors Reduces Excitotoxicity in Auditory Neurons" (#80) takes place Sunday, February 15, at 1:00 p.m. in the Grand Ballroom.
How Your Brain Deciphers Cocktail Party Banter
Anyone who has tried to carry on a conversation in a roomful of talkers knows how difficult it can be to concentrate on what one person is saying while tuning everyone else out. Researchers at the University of Maryland, Johns Hopkins University, and Starkey Laboratories, Inc. have a better picture of how the brain manages this feat. Using magnetoencephalography (MEG), an imaging technique that measures magnetic fields produced by changes in the brain's electrical activity, the researchers played two competing audio streams into the ears of 26 healthy volunteers and asked them to listen to one stream while ignoring the other. One group concentrated on a faster-paced series of beeps while the second group focused on a slower beep pattern; the groups later switched tasks to focus on the other audio stream. The researchers also introduced an occasional change in the rhythm to find out if the study volunteers noticed. Among their results, researchers found that people listening to one stream did not detect pattern changes in the other stream. In addition, although the brain showed neural activity representing both audio streams, the amount of neural activity was much stronger and more in sync for the stream on which a person was concentrating.
The poster "Competing Streams at the Cocktail Party - A Neural and Behavioral Study of Auditory Attention" (#879) takes place Wednesday, February 18, at 1:00 p.m. in the Grand Ballroom.
For Implant-Wearing Guitarist, Hearing the Notes Not Necessary for Staying on Key
The cochlear implant is a remarkable technology that helps people with severe hearing loss to understand speech, even when on the telephone. Listening to music, however -- even a simple melody -- remains difficult for many implant wearers. Researchers at the University of California, Irvine, and Peking University, Beijing, have found one cochlear-implant-wearing musician who is able to tune his guitar without help from an electronic tuner. Instead of listening to the tones of the strings, the guitarist counts the beats between mismatched notes. This is based on the principle that when two notes are out of tune with one another, an audible pulsing or beating occurs. The greater the mismatch, the faster the beats. Musicians with normal hearing frequently listen to the pulsing in addition to the tones to make sure their instruments are properly tuned. After plugging the guitarist's speech processor into a computer, the researchers found that the output of the processor clearly reflected this same beating, which implant users are known to reliably detect. The researchers suggest that this is another application, previously unknown, for cochlear implant wearers.
The poster "Accurate Tuning of a Guitar by a Cochlear Implant Musician" (#439) takes place Monday, February 16, at 1:00 p.m. in the Grand Ballroom.
For more information about the Association for Research in Otolaryngology, visit their Web site at www.aro.org.
NIDCD supports and conducts research and research training on the normal and disordered processes of hearing, balance, smell, taste, voice, speech and language and provides health information, based upon scientific discovery, to the public. For more information about NIDCD programs, see the Web site at www.nidcd.nih.gov.
The National Institutes of Health (NIH) -- The Nation's Medical Research Agency -- includes 27 Institutes and Centers and is a component of the U. S. Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical, and translational medical research, and it investigates the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.