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Summer 2015

Feature Stories

In the largest study to date of hearing loss among Hispanic/Latino adults in the U.S., researchers report that nearly 1 in 7 has hearing loss, a number similar to the general population prevalence. The analysis also looked at the differences among subgroups and found that Hispanics of Puerto Rican descent have the highest rate of hearing loss, while Mexican-Americans have the lowest. The researchers found several potential risk factors for hearing loss that are also common among the general U.S population, including age, gender, education level, income, noise exposure, and diabetes. In contrast, some general risk factors were not found to play a significant role in hearing loss among Hispanics; these include smoking, obesity, history of cardiovascular disease, and stroke. The study, which was supported by the National Institutes of Health (NIH), was published online May 28, 2015, by JAMA Otolaryngology—Head and Neck Surgery.

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Using both neuroimaging and behavioral assessments on study volunteers with aphasia, an NIDCD-funded research team led by scientists from Drexel University and the Moss Rehabilitation Research Institute were able to map different language impairments to specific brain regions to help better understand the basic organization of the human language system. Aphasia is a disorder that results from damage to portions of the brain that are responsible for language, and often occurs in people who have had a stroke or head injury. The findings, published online April 16, 2015, in Nature Communications, may lead to improved diagnosis and treatment of language impairments.

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Nearly 1 in 12 children ages 3-17 has had a disorder related to voice, speech, language, or swallowing infographic.Nearly 1 in 12 children ages 3–17 has had a disorder related to voice, speech, language, or swallowing in the past year, according to results of the first nationally representative survey of these disorders among children in the U.S. Data from a supplement to the 2012 National Health Interview Survey (NHIS) also reveal that more than half of children with a communication or swallowing disorder receive intervention services. Published in a June 2015 data brief by the Center for Disease Control and Prevention's National Center for Health Statistics (NCHS), the study was conducted by scientists from NCHS and the NIDCD.

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Recent NIDCD and NIH Research News

Hearing, Balance

Some genetic conditions may be more common than previously thought, according to a new study by NIH scientists. By analyzing the DNA of about 1,000 healthy individuals, the researchers found that roughly 100 have a genetic mutation associated with a genetic disease. Upon follow-up, 34 of these were found to have signs of the condition linked to their mutation, indicating that 3 percent or more of the U.S. population may have a genetic condition. This compares to previous estimates of less than 0.02 percent. This work suggests that the prevalence of genetic conditions, including those that cause hearing impairment, have been underestimated, especially in people who are mildly affected.

A study in mice by researchers at Georgia State University and the University of Rochester has shown that an existing anti-stroke medicine is also an effective treatment for middle-ear infections. The researchers found that topical administration of the drug vinpocetine suppressed inflammation and the production of mucus induced by Streptococcus pneumonia bacteria, a common cause of middle ear infections. Drug treatment improved bacterial clearance and helped prevent loss of hearing, a frequent complication of ear infections. The findings suggest that repurposed vinpocetine could provide a valuable alternative to antibiotics in treating one of childhood's most common ailments.

Tinnitus is commonly described as a ringing in the ears, but it also can sound like roaring, clicking, hissing, or buzzing. Although little is known about the cause of the condition, researchers at the University of Buffalo, the State University of New York, have uncovered the regions of the rat brain that are activated by tinnitus and the related condition, hyperacusis, in which every day sounds seem unbearably loud. The abnormal brain activity, rather than being limited to a single region, was found to extend to several areas including the amygdala, the reticular formation, and the hippocampus. The researchers used this data to create a model they can now use to analyze the underlying causes of tinnitus and hyperacusis.

A study in mice performed at the University of Buffalo, the State University of New York, has shown that continual exposure to noise can change the structure and behavior of cells of the auditory nerve, which relay sound signals from the ear to the brain. In mice exposed to a noisy environment, the cells released lower levels of neurotransmitters, molecules they use to communicate with other nerve cells, compared to cells from mice reared in a quiet habitat. In addition, the cells from noise-exposed mice increased the size of their synaptic endings, the region where neurotransmitters are stored, suggesting a boost in production of these key signaling molecules. The changes reveal how the auditory system adapts to noisy conditions by not depleting its stores of neurotransmitters, thereby enabling the detection of new sounds in the midst of background noise.

Researchers at the University of Iowa have reported that tinnitus, a condition in which people perceive ringing, roaring, clicking, hissing, or buzzing sounds that are not really there, is associated with neural activity across extensive regions of the brain. The researchers were able to take advantage of a rare opportunity to record neural activity directly from the brain of a person being prepared for epilepsy surgery. (The patient also had a typical pattern of tinnitus.) By comparing brain activity in the patient in periods when tinnitus was relatively strong and weak, the researchers showed that tinnitus-linked brain activity encompasses almost the entire auditory cortex—the region where sounds are processed—along with other parts of the brain. In contrast, the brain's responses to a real sound similar to the subject's tinnitus were localized to a tiny area. The findings provide a better understanding of tinnitus and may point toward new treatment approaches.

By sequencing the DNA of members of a multi-generational Tunisian family with a long history of hereditary deafness, researchers at the University of Miami Miller School of Medicine have identified the underlying gene mutation. The gene, which encodes a protein called DCDC2a, appears to control the length of a structure called the kinocilium, which contributes to the development and function of stereocilia. (Stereocilia are key components of hair cells, the sensory cells in the inner ear that enable us to hear.) The discovery provides valuable insights into a molecular mechanism that causes deafness and could lead to the development of novel treatments to combat a wide range of congenital hearing defects.

Scientists at the Cold Spring Harbor Laboratory, New York, have mapped changes in communication between nerve cells in the brain as rats learn specific responses to particular sounds. The researchers found that as the rats learned to associate particular sounds with the locations of concealed food, the connections between nerves in the auditory cortex, where sounds are processed, and the striatum, where behavior is controlled, strengthened. By dissecting the brains of the trained rats, the researchers were also able to map the lines of communication between the two brain regions according to frequency of the sound and direction of the rats' movements. The results provide additional insight into how the brain processes sensations and forms memories to inform behavior.

A team of scientists at the Northwestern University Feinberg School of Medicine has discovered a neuronal connection in mice between the cochlea and the brain that signals intense and potentially damaging noise. The researchers found that the newly discovered neurons are only activated by dangerously loud noises and that they are distinct from those used to transmit normal sounds to the brain. The findings show that the auditory system has developed a mechanism for detecting sounds that could harm the delicate and irreplaceable sensory cells in the inner ear. In addition, the discovery may shed light on conditions such as hyperacusis, in which everyday sounds seem painfully loud, and tinnitus, a condition in which people perceive ringing, roaring, clicking, hissing, or buzzing sounds that are not really there.

Researchers at Draper Laboratory, Cambridge, Massachusetts, in collaboration with Massachusetts Eye and Ear, have developed a micropump device that can deliver a desired concentration of drug to the inner ear of guinea pigs. In addition to delivering medicines for hearing loss directly to the inner ear, the device can also sample the inner ear fluid, enabling scientists to study how a candidate drug is processed over time. The device represents a significant advantage over currently used delivery methods, which include repeat injections into the middle ear. The scientists are working toward adapting the device for implantation in people and expect it could be ready for clinical trials in three years.

Salicylates, a class of non-steroidal inflammatory drugs (NSAIDs), halt the growth of cultured vestibular schwannoma cells, according to a pre-clinical study from Massachusetts Eye and Ear. Vestibular schwannomas, also known as acoustic neuroma, are tumors that grow from the nerves that supply the inner ear, often causing hearing loss, tinnitus, and dizziness or balance problems. They can also lead to facial numbness or paralysis; large tumors can become life-threatening. The study showed that salicylates block the cells' growth by inhibiting an enzyme called cyclooxygenase 2, which is present at high levels in vestibular schwannomas. Current treatments for growing or symptomatic vestibular schwannomas rely on surgery and radiation, which can lead to significant complications. If confirmed in clinical trials, the findings could offer a new and less invasive way to control the tumors.

Aminoglycosides, the most commonly used class of antibiotics, are often necessary to treat certain types of life-threatening infections, but their use also carries the risk of hearing loss or deafness. Now, researchers at the Stanford University School of Medicine report that they have developed a modified version of an aminoglycoside that works effectively in mice without causing deafness or kidney damage, another common side effect. Using data on the three-dimensional structure of an aminoglycoside called sisomicin, the researchers targeted the parts of the molecule that are not involved in mediating the drug's antimicrobial activity. The newly designed aminoglycoside, N1MS, is unable to enter, and thereby harm, the delicate sensory cells of the inner ear. The researchers' next plan is to test N1MS in clinical trials.

A team of researchers led by scientists at San Diego State University report that adults who are HIV-positive are more likely to experience hearing loss than adults who are not infected with HIV, regardless of the severity of disease progression or the use of and adherence to HIV medications. Study participants were recruited from two long-standing NIH-supported studies in the Baltimore and Washington, D.C., areas and included 262 men and 134 women. Each participant had a standard clinical hearing test at an audiology clinic, and the results showed that the HIV-positive men and women had trouble hearing both the low and the high tones, with an average increase in hearing threshold of about 10 decibels. In the future, the researchers plan to investigate the underlying mechanisms for HIV-associated hearing loss.

Taste, Smell

Research from the Monell Center has revealed that tumor necrosis factor (TNF), an immune molecule that promotes inflammation, also helps regulate sensitivity to bitter taste. The researchers found that, compared to normal mice, mice engineered to lack TNF were less sensitive to bitter taste, yet were equally sensitive to sweet, umami, salty, and sour tastes. The results suggest that TNF regulates bitter taste in normal mice and that elevated TNF levels associated with infection or inflammation may cause foods to taste more bitter. The findings provide a possible explanation for the taste system abnormalities and decreased food intake that can be associated with infections, autoimmune disorders, and chronic inflammatory diseases.

The decades' worth of data that has been collected about the billions of neurons in the brain is astounding. To help scientists make sense of this wealth of information, researchers at Carnegie Mellon University have used data mining to create a publicly available website that acts like Wikipedia, indexing physiological information about neurons. The researchers mined neuronal electrophysiological data from more than 10,000 published papers and ultimately published standardized information about 100 different types of neurons. The resource, which users can add to or refine, is expected to advance research on neuronal function.

Neuroscientists at the University of California, San Diego School of Medicine, have identified a type of neuron that appears to help tune, amplify, and dampen neuronal responses to odors. Working in mice, the researchers used a technology called optogenetics to de-activate inhibitory neurons—neurons that reduce neuronal signaling—in the olfactory cortex, the region of the brain where odors are processed. They found that in the absence of these neurons, odors triggered an increase in "background" brain activity—activity unrelated to direct processing of odors. The results indicate that these inhibitory neurons increase the signal-to-noise ratio of brain activity, possibly improving the ability to discern different odors. The researchers speculate that these same cells may also help prevent excessive excitation in the olfactory cortex that has been linked to epilepsy.

Voice, Speech, Language

A team of New York University neuroscientists has identified a part of the brain exclusively devoted to processing speech. The researchers used functional magnetic resonance imaging (fMRI) to gauge how multiple parts of the study volunteers' brains responded to speech and other sounds, such as fireworks and dogs barking. As expected, all types of sounds stimulated activity in the auditory cortex, the area of the brain where sounds are processed, but only speech sounds activated another region called the superior temporal sulcus (STS). The results suggest that the STS is dedicated to managing speech, and help settle a long-standing debate about the existence of an area of the brain exclusively devoted to speech.

Someone who cannot write a grammatically correct sentence may be able say it aloud flawlessly, according to research from Johns Hopkins University, suggesting that writing and speaking are processed in different parts of the brain. The researchers studied five volunteers who developed aphasia as a result of stroke. Aphasia is a disorder that impairs the expression and understanding of language, as well as reading and writing. The researchers found that four of the volunteers had trouble using the proper suffixes on written words but could say them correctly. The last individual had the opposite problem—trouble with speaking, but normal writing ability. The findings could help educators as they teach children to read and write and could lead to the development of new therapies for aphasia.

Researchers at the Beckman Institute at the University of Illinois, Urbana-Champaign, have developed a new magnetic resonance imaging (MRI) technique that can reveal the vocal neuromuscular movements of singing and speaking at 100 frames per second, some 10 times faster than the typical MRI. The researchers are using the technique to study whether regular singing among older adults improves the structure of the larynx, giving them stronger, more powerful voices. By capturing how the dozens of different muscles in the chest, neck, jaw, tongue, and lips work together to produce sound, the technique may shed light on changes to the speech process during aging.

Although difficulty swallowing is a health problem associated with aging, it has been unknown whether the condition is a natural part of aging or stems from age-related disease, such as Parkinson's disease. A team of researchers at the University of Missouri has shown that difficulty swallowing appears to be a normal part of aging. By studying the swallowing function of healthy mice over their two-year lifespan using a technique called videofluoroscopy, they found that the mice exhibit many of the same symptoms as healthy aging human adults, such as slower swallowing and impaired tongue function. The researchers now plan to use the model to determine why age-related dysphagia occurs and identify ways to prevent it. The findings also help set the stage for potential new therapies to delay or reverse swallowing disorders.

In speech disorders research, trained professionals are often used to evaluate patients' progress over the course of treatment by listening to speech sounds and rating them. Now, researchers at New York University have found that listeners recruited online through a crowdsourcing platform are just as effective at rating sounds as experienced listeners. When experienced and crowdsourced listeners were asked to rate recordings of 100 words containing the "r" sound collected from children with trouble pronouncing the sound, there was a very high level of overall agreement between the two groups. By expanding access to independent, unbiased listeners, crowdsourcing in speech disorders research has the potential to save time and money, as well as to improve the rigor of the results.

In the first study to use magnetic resonance imaging (MRI) to examine the brains of both children and adults who stutter, researchers at the University of Alberta have discovered that stuttering is associated with abnormal development of Broca's area, a region of the brain that controls speech. The researchers studied MRI images of the brains of 116 males between the ages of 6 and 48 years, roughly half of whom stuttered. They looked at 30 regions of the brain, and the only abnormality they found was that the normal thinning of the cortical grey matter that comes with age did not occur in Broca's area in the participants who stuttered. The difference may reflect an improved efficiency of brain function over time among people who don't stutter compared to people who do. In the future, scientists may be able to develop new therapeutic approaches based on how the brain changes in children who stutter and then recover.

NIDCD Highlights

The Institute of Medicine (IOM) is conducting a consensus study, sponsored by the NIDCD, the National Institute on Aging, the Centers for Disease Control and Prevention, the Food and Drug Administration, and the Hearing Loss Association of America, on accessible and affordable hearing health care for adults.

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The NIDCD hosted several visitors from the U.S. House of Representatives and the Senate.

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Alberto Rivera-Rentas, Ph.D., has joined the National Institute on Deafness and Other Communication Disorders as the Institute's research training officer. Dr. Rivera-Rentas takes over the Institute's research training officer responsibilities from Daniel Sklare, Ph.D., who retired in January. 

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Audiologists and other research staff from the NIDCD Audiology Unit play a key role in research at the NIH's Clinical Center on Niemann-Pick disease type C (NPC), a debilitating and often fatal genetic disease. NIDCD research audiologists are closely monitoring the hearing of volunteers in a clinical treatment study being conducted through a public-private partnership between NIH and biotech company Vtesse, Inc. Scientists from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) are leading the phase I clinical trial of cyclodextrin, a promising new therapy for NPC.

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Gordon Blackistone Hughes, M.D., clinical trials coordinator for the NIDCD since 2008, died suddenly on February 15. Dr. Hughes was a respected clinician, researcher, and colleague, and during his time at the NIDCD he oversaw the development of a young but vigorous clinical trials program.

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Dennis Drayna, Ph.D., chief of NIDCD's Laboratory of Communication Disorders, Section on Systems Biology of Communication Disorders, was a special guest in the 500th podcast of StutterTalk, a popular and long-running podcast on stuttering. The program, which was posted on the StutterTalk website on March 4, marked Dr. Drayna's fourth appearance on the show. During the podcast, Dr. Drayna discussed the role of genetics in stuttering.

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In May, the NIDCD celebrated Better Hearing and Speech Month, an annual observance sponsored by the American Speech-Language-Hearing Association (ASHA) to raise awareness about communication disorders. This year's theme was "Early Intervention Counts." The NIDCD marked the observance by highlighting recently-funded research advances in communication disorders, developing new shareable images for social media, and promoting the Institute's science-based information on communication disorders.

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To encourage healthy voice habits, the NIDCD observed World Voice Day, sponsored by the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS), on April 16. This year's motto was "VO!CE, the original social media," reminding us that we rely heavily on our voices to communicate—whether at school, work, or play. In honor of this year's social media theme, the NIDCD developed an infographic highlighting the causes and prevention of voice disorders, and research to enhance diagnosis and treatment.

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Earlier this year, President Obama launched the Precision Medicine Imitative (PMI), a research initiative that aims to accelerate progress toward prevention and treatment strategies that take individual variability into account. As a partner in the initiative, NIH is focusing on two main components: a near-term focus on cancers and a longer-term aim to build general knowledge about the whole range of health and disease.

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To advance its mission and in response to a request from Congress, the NIH is developing a five-year, NIH-wide Strategic Plan. The plan will outline a vision for biomedical research that will pursue fundamental knowledge about the nature and behavior of living systems and apply that knowledge to extend healthy life and reduce illness and disability. NIH senior leadership and staff from all 27 Institutes, Centers, and Offices (ICOs), with input from the Advisory Committee to the Director of NIH, have developed a framework for the plan.

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In March, NIH celebrated Women's History Month by adding women scientists to the pages of Wikipedia, the free online encyclopedia that has become the go-to reference for millions of Internet users. The goal of the event was to use NIH's wide array of information, photos, and histories about influential women scientists and researchers to improve the world's awareness and knowledge of contributions of women in science. NIDCD grantee Linda Buck, Ph.D., who was awarded the 2004 Nobel Prize in Physiology or Medicine for her work clarifying how the olfactory system works, was among the scientists whose pages were enhanced as part of the event.

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The Spring issue of NIH MedlinePlus magazine featured several stories on hearing loss, including information on symptoms, causes, prevention, and assistive devices. The magazine also featured highlights of some NIDCD-funded research on the mechanistic processes that occur during inner ear tip link growth and regeneration. 

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Sounds surround us. We enjoy many of them—such as music, birdsong, and conversations with friends. But loud or long-lasting noises—from motors, power tools, and even headphones—can permanently damage our hearing. The January edition of NIH News in Health, a monthly newsletter from the National Institutes of Health, focused on the causes of noise-induced hearing loss and steps you can take to protect your hearing.

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