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National Institute on Deafness and Other Communication Disorders

How Your Brain Understands What Your Ear Hears

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Appendix I

More About the National Institutes of Health

Begun as a one-room Laboratory of Hygiene in 1887, the National Institutes of Health today is one of the world’s foremost medical research centers and the federal focal point for medical research in the United States.

What Is the NIH Mission and Organization?

The NIH mission is to uncover new knowledge that will lead to better health for everyone. NIH works toward that mission by

NIH is one of eight health agencies of the Public Health Service, which, in turn, is part of the U.S. Department of Health and Human Services. NIH’s institutes and centers encompass 75 buildings on more than 300 acres in Bethesda, Md. The NIH budget has grown from about $300 in 1887 to more than $23.5 billion in 2002.

What Is the Goal of NIH Research?

Simply described, the goal of NIH research is to acquire new knowledge to help prevent, detect, diagnose, and treat disease and disability, from the rarest genetic disorder to the common cold.

How Does NIH Help Scientists Reach This Goal?

Approximately 82 percent of the investment is made through grants and contracts supporting research and training in more than 2,000 research institutions throughout the United States and abroad. In fact, NIH grantees are located in every state in the country. These grants and contracts make up the NIH Extramural Research Program.

Approximately 10 percent of the budget goes to NIH’s Intramural Research Programs, the more than 2,000 projects conducted mainly in its own laboratories.

The Intramural Research Programs are central to the NIH scientific effort. First-rate intramural scientists collaborate with one another regardless of institute affiliation or scientific discipline and have the intellectual freedom to pursue their research leads in NIH’s own laboratories. These explorations range from basic biology, to behavioral research, to studies on treatment of major diseases. NIH scientists conduct their research in laboratories located on the NIH campus in Bethesda and in several field units across the country and abroad.

NIH Research Grants

Final decisions about funding extramural research are made at NIH headquarters. But long before this happens, the process begins with an idea that an individual scientist describes in a written application for a research grant.

The project might be small, or it might involve millions of dollars. The project might become useful immediately as a diagnostic test or new treatment, or it might involve studies of basic biological processes whose practical value may not be apparent for many years.

Peer Review

Each research grant application undergoes a peer-review process.

A panel of scientific experts, primarily from outside the government, who are active and productive researchers in the biomedical sciences, first evaluates the scientific merit of the application. Then, a national advisory council or board, composed of eminent scientists as well as public members who are interested in health issues or the biomedical sciences, determines the project’s overall merit and priority in advancing the research agenda of the particular NIH funding institute.

Altogether, about 38,500 research and training applications are reviewed annually through the NIH peer-review system. At any given time, NIH supports 35,000 grants in universities, medical schools, and other research and research training institutions both nationally and internationally.

Who Are the Scientists NIH Supports?

Scientific progress depends mainly on the scientist. About 50,000 principal investigators—working in every state and in several foreign countries, from every specialty in medicine, every medical discipline, and at every major university and medical school—receive NIH extramural funding to explore unknown areas of medical science.

Supporting and conducting NIH’s extramural and intramural programs are about 15,600 employees, more than 4,000 of whom hold professional or research doctorate degrees. The NIH staff includes intramural scientists, physicians, dentists, veterinarians, nurses, and laboratory, administrative, and support personnel, plus an ever-changing array of research scientists in training.

The NIH Nobelists

The roster of those who have conducted NIH research or who have received NIH support over the years includes the world’s most illustrious scientists and physicians. Among them are 97 scientists who have won Nobel Prizes for achievements as diverse as deciphering the genetic code and identifying the causes of hepatitis.

Five Nobelists made their prize-winning discoveries in NIH laboratories. You can learn more about Nobelists who have received NIH support at

What Impact Has NIH Had on the Health of the Nation?

NIH research has played a major role in making possible the following achievements of the last few decades:

NIH Research in the 21st Century

NIH has enabled scientists to learn much since its humble beginnings. But many discoveries remain to be made:

These are some of the areas where NIH’s investment in health research promises to yield the greatest good for the greatest number of people.

For more about NIH, visit its Web site at

Appendix II

More about the NIDCD and Its Research

In 1988, Congress established the National Institute on Deafness and Other Communication Disorders as a separate Institute within the National Institutes of Health (NIH). Commonly referred to as the NIDCD, this Institute supports and conducts research and research training on normal mechanisms as well as diseases and disorders of hearing, balance, smell, taste, voice, speech, and language. These processes of sensing and interpreting are fundamental to the way individuals perceive the world around them and to their ability to communicate effectively with others.

In the past few years, NIDCD-supported scientists have made remarkable progress in research on human communication and its disorders. This progress has been further accelerated by research supported by other institutes at NIH and is now providing the foundation for current and future research to achieve an important goal: to help individuals with communication and sensory-system disorders.

The NIDCD has developed a strategic plan to draw attention to extraordinary research opportunities and compelling needs in the area of communication and sensory disorders. While this plan assists the NIDCD in focusing on specific areas of research, it is not intended to be an all-encompassing master plan for funding. The NIDCD’s first priority continues to be the funding of high-quality research conceived and initiated by members of the research community that will help achieve the goals and objectives of the NIDCD.

What Are Some of the Problems the NIDCD Addresses?

In this information age, communication and technology skills will be central to a successful life for all Americans. The labor force of the 21st century will require intense use of these skills. However, for the one in six Americans who has communication disabilities, as well as their families who support them, each day can be a challenge. The simple acts of speaking, listening, and making wants and needs understood are often impossible. The days are often very challenging

Communication disorders have a major impact on education, employment, and the well being of Americans.

A Few Vital Statistics

Birth and Early Childhood


What Progress Has Been Made?

What We Know

Past research has produced many significant discoveries and technologies that improve our ability to identify and treat people with communication problems. Because of research advances,

What We Don’t Know

But research findings also teach us how much more there is to know. For example, we need to learn

To achieve the greatest benefit from finite research dollars, the NIDCD considers the effects that communication disorders have on the American people as well as areas that offer the greatest opportunity for significant progress at this time. After weighing these factors with scientists and representatives of the public, the NIDCD has identified a number of future research opportunities.

Future Research Opportunities

Why All This Interest in Research on Genes?

Doctors and scientists have long known that well-defined disorders of hearing and other aspects of human communication (language, speech, voice, etc.) often run in families. Changes called mutations in one or a few genes can have a dramatic effect on very complex functions, including hearing, speech, and language. Genes contain all the information that tells a cell how to make proteins. These proteins are the building blocks that determine the structure and function of all living cells, which in turn form the tissues, organs, and organ systems within the human body. Humans have 30,000 to 35,000 different genes. (This recent finding was somewhat surprising for researchers; previous predictions had ranged from 80,000 to 150,000 genes.) As scientists and physicians define the structure of the human genome, the identification of genes involved in human communication and communication disorders becomes more straightforward. Finally, learning about the nature of proteins made from these genes allows us to understand more about new and unsuspected cellular processes that are essential for effective communication. Once understood, these proteins may someday be targets for new treatment strategies. The willingness and generosity of families with hereditary communication disorders who agree to participate in studies with clinicians and scientists are what makes this research on gene discovery possible.

Understanding Leads to Education and Prevention

Changes in genes contribute to many communication disorders, either directly, by causing a critical group of cells to malfunction, or indirectly, by increasing sensitivity to damage caused by environmental factors such as noise, drugs and medications, or infections. Research aimed at understanding the identity and function of these genes may one day allow us to diagnose and classify patients with communication disorders based on specific genetic changes, in addition to recognizable symptoms. This knowledge could be directly applied to a clinical setting. For example, children diagnosed at birth with a mild hearing loss, who have a gene mutation that will cause progressive hearing loss and deafness by their teens, might be given additional educational help early in life so they may function better in the future. Such children and their parents might also be instructed to avoid noisy settings (rock concerts, loud radios, etc.), certain occupations, or certain medications that could cause the hearing loss to progress more rapidly.

Scientists and Physicians Can Find the Genes

To use genetics to prevent, diagnose, and treat communication disorders, we must first learn which genes are essential for the communication senses to function normally. Researchers can pinpoint which genes are critical to hearing by studying mice that are deaf due to mutations in certain genes since these same genes often affect hearing in humans. In mice, scientists can determine the function of a single gene by systematically altering the gene and observing any changes that occur. Much more can be learned about human hearing by applying the powerful tools of genetics to mice.

Many communication disorders are complex, with multiple components and causes. Some disorders are caused by complex genetic traits in which multiple genes are involved. Others are directly associated with a single underlying problem that has multiple effects. One gene can affect how other genes function, and small differences in several genes can cumulatively affect one’s susceptibility to a disorder. Thus, it is necessary to understand the complex interactions of these genetic factors. Such knowledge could lead to the development of effective prevention and treatment strategies.

Nongenetic Factors

Not all communication disorders have a genetic basis. For example, hearing loss can be caused by infections, noise damage, or certain medications.

Infants who experience hearing loss can have difficulty learning to speak or understanding language later in life, if appropriate education and training are not provided. Impaired language skills affect all aspects of our ability to function in today’s communication-driven society. Language impairment also can be caused by brain-injury or brain-developmental problems, in addition to childhood hearing impairment. Diseases of the larynx (voice box) can be caused by infections or by the presence of a tumor. More research is needed to identify additional nongenetic causes of communication disorders.

Increasing Potential for Recovery: How the Body Creates New Cells

healthy hair cell
Electron micrograph of a healthy hair cell.

Hair Cells in the Inner Ear

Most parts of the body that are damaged due to illness or injury have the ability to heal by regenerating healthy cells to replace those that have been damaged or lost. Until the recent past, the highly specialized hair cells of the inner ear, which are critical to hearing and balance, were considered irreplaceable if injured or destroyed. Recent discoveries in birds, however, confirm that specialized inner ear hair cells that have been destroyed by very loud noises can be replaced by regeneration of healthy hair cells. This research has inspired hope that damaged inner ear hair cells in humans, one of the major underlying causes of hearing loss, could be repaired or replaced. Future research is needed to explore whether the same processes that produce inner ear hair cells during development of the human embryo could be reactivated to achieve hair-cell regeneration in older individuals.

Sensory and Nerve Cells in the Nose

In contrast to the hair cells of the inner ear and many other sensory cells and neurons, the sensory nerve cells of the human olfactory system, our sense of smell, shows a remarkable ability to regenerate. The ability of these newly restored cells to make appropriate connections to brain regions that respond to specific odors needs to be intensively studied. Research identifying what factors make this possible could lead to the design of intervention strategies promoting the regeneration of nerve cells in other parts of the nervous system.

Recovering Speech and Language Ability

Adults who suffer brain damage as a result of a stroke often have problems expressing their thoughts. These speech and language disorders severely compromise their ability to communicate and decrease their quality of life. In contrast, infants and young children who have suffered comparable brain damage from birth injuries, childhood trauma, or extensive brain surgery sometimes develop or recover speech and language abilities. If researchers can determine why young children have the ability to recover from severe brain damage, then they may learn how adults can be helped to do the same.

Sensory cells in the hearing and balance organs in the inner ear develop connections with specific brain regions early in life. We know that the brain is particularly receptive to forming these connections at certain times in the young child’s life. If these time-sensitive opportunities are missed because sensory information is not being transmitted to the brain, the ability to develop critical brain connections or pathways may be lost forever. This could occur, for example, in an infant with undetected severe hearing loss. Research is needed to identify these critical “windows of opportunity” for developing brain connections essential for communication. Important research findings in this area have already stimulated interest in major public health efforts, such as the screening of millions of newborn babies for hearing loss each year.

From Sensing to Interpreting

Understanding Human Communication

Human communication relies on complicated perceptual skills—taking information from the outside world through the senses (hearing, vision, touch, taste, and smell) and interpreting it in a meaningful way. Human communication also requires mental abilities, such as attention and memory. We still do not understand exactly how all of these processes work and interact, or how they malfunction in the case of communication disorders. But we do know that many communication disorders are caused by problems that occur even when the senses (such as hearing) are completely functional. Recently, new methods have been developed to study what happens after information is received by the sense organs. It is now possible to view parts of the brain directly while they’re at work through computerized imaging technology, and to see changes as information flows from sensory organs to the brain. For example, a functional magnetic resonance imaging (fMRI) scan of the brain can be used to observe activity as language information is received, processed, and interpreted. Research studies that use powerful imaging techniques such as fMRI are especially valuable in the study of speech and language because these important forms of communication cannot be studied in animals.

Processing Information in the Brain

Aside from the advances being made in brain imaging, new ways are emerging for studying the basic organization and operation of human communication. Information processing in the brain involves the successive activation or stimulation of nerve cells. In other words, information moves continuously from one nerve cell to another like electricity moving along a wire. This activation process takes place when chemicals in one nerve cell are released, stimulating activity in the adjacent nerve cell. Research advances have provided new tools that allow scientists to determine the nature of chemicals that are found in the nerve-cell networks devoted to human communication. This knowledge could lead to new treatment strategies for individuals with communication disorders caused by abnormalities in critical nerve-cell networks.

Applying New Knowledge

As described in the previous sections, scientists have made great progress in recent years toward the goal of understanding human communication and its disorders. These advances have occurred as a result of unprecedented breakthroughs in genetics, other basic sciences, and technology. We can expect continued progress to be made as additional genes associated with specific communication disorders are identified and their functions revealed, and as more is learned about the function of the brain and other organs that are important for communication.

Although advances in basic research are of great theoretical and scientific importance, they represent only a first step toward improving the lives of individuals with communication disorders. The next step is to apply knowledge gained from basic research to clinical studies in which the ultimate goal is to develop the most appropriate and effective means of preventing, diagnosing, and treating communication disorders. For example, you may be familiar with hearing screening programs that have been established around the country to identify infants and young children who have significant hearing loss. The technology that enables us to screen newborns is a result of basic laboratory studies that measure the electrical signals from auditory centers in the brain (auditory brainstem response, or ABR) and tiny sounds generated by the inner ear (otoacoustic emissions). Because babies who are hearing-impaired can now be identified in their infancy, researchers can conduct clinical trials to establish and validate the most effective educational programs and treatments (including hearing aids or cochlear implants) and to determine the age at which treatment should begin for maximal success.

Clinical research is also needed to describe the range of differences that occur in human communication over a person’s life span, such as production of speech sounds, hearing acuity, odor detection (sense of smell), and ability to maintain balance. These differences may then be related to an underlying gene or genes, which may help identify people who are at greater risk of developing problems. Clinical trials are also necessary to tell us which medical and behavioral interventions are safe and effective treatment methods for communication disorders. These may include evaluations of medications to treat Ménière’s disease and autoimmune hearing loss, light therapy to treat warts on the vocal cords (laryngeal papillomas), electrical stimulation and medications to treat ringing in the ears (tinnitus), imaging techniques to assess brain damage and predict recovery from stroke, and physical therapy involving special positioning of the head for loss of balance (positional vertigo).

The NIDCD is committed to supporting research to develop devices that improve or restore communication abilities, or prevent communication disorders. Advances in basic science research and in bioengineering contributed to the development of the electrolarynx to restore speech after the removal of the voice box (larynx); digital, programmable hearing aids that fit inside the ear canal; cochlear and brainstem implants to improve the communication abilities of adults and children with severe-to-profound hearing loss; and video-game-like computer programs for treatment of disorders that may be associated with learning disabilities. Although these inventions emerged from basic knowledge regarding human communication, the ultimate success of current and future devices can only be determined by carefully designed clinical research studies. These clinical research studies are an important priority for the NIDCD.

For more information, contact

Office of Health Communication and Public Liaison
National Institute on Deafness and Other Communication Disorders
National Institutes of Health
31 Center Drive, MSC 2320
Bethesda, MD 20892-2320
Voice: (800) 241-1044
TTY: (800) 241-1055

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