Why NIDCD Supports Voice, Speech, and Language Research
Communication allows us to participate in society and is a defining characteristic of what it is to be human. Other organisms clearly communicate; however, in no other species does it appear that communication—specifically the use of language in communication—is as highly developed as in humans, nor as central to an organism’s function and identity. Communication impairments that involve voice, speech, or language often limit a person’s ability to participate in society, whether the activity is educational, occupational, or social. In addition, because effective communication is needed to get aid in life-threatening situations, loss of communication can put people at risk for compromised physical safety and survival.
Human communication systems rely on the sensory functions of the peripheral organs responsible for hearing, balance, taste, and smell, located in the middle and inner ear, nose, mouth, and throat. They also involve vision (used for sign language and visible speech) and the development of abstract linguistic representations and memory mechanisms, located centrally in the brain. Additionally, communication systems rely on the motor functions of the hands and arms (for sign language and co-speech gesture) and on the peripheral organs of speech production, which include the diaphragm, vocal folds, tongue, lips, and other oral structures. These structures are involved in other important processes such as swallowing, which can be impaired in many of the same diseases or disorders that affect speech.
Human communication requires the brain’s interpretation of the complex sensory signals collected by the peripheral organs and the production of signals to choreograph the muscles involved in speaking and signing. The interplay between central and peripheral signals, genetics, and environment make language acquisition a vulnerable process. The causes of many voice, speech, and language disorders remain poorly understood and the path to treatment is often uncertain. Gaps in evidence for age-appropriate clinical goals, targets of intervention, and expected trajectories of change challenge the development of effective treatment. Researchers are only beginning to understand in sufficient detail the developmental course of speech and language markers during childhood that serve as a guide for clinical interventions suited to particular levels of development. In addition, greater documentation is needed on the decline in speech and language due to aging in order to assess clinical intervention targets for sensory and speech, language, or voice disorders.
While spoken language is the primary way people communicate, it is not the only way. The symbolic nature of language allows us to attribute meaning through not only the voice, speech, and hearing, but also using visual-manual modes of communication, most notably the use of sign languages and augmentative communication systems. NIDCD supports research to understand these communication systems, their acquisition and development, and their use when spoken language systems are damaged by trauma or degenerative diseases and disorders, or when speech is difficult to acquire due to early hearing loss or damage to the nervous system. Enhanced understanding of visual-manual language systems opens a window into general human cognition.
Voice, speech, or language impairments affect a wide range of educational, economic, and personal and public health areas. Some disorders affecting communication and swallowing are associated with substantial health-related morbidity and mortality. For example, swallowing impairments commonly lead to pneumonia, malnutrition, dehydration, and even death.100, 101
Infancy and Childhood
Hearing loss in infancy and childhood gives rise to difficulties in acquiring spoken and written language skills. Children who are deaf are at great risk for delays in learning to read. Only 10 percent of deaf students graduate from high school reading above the eighth grade level102 and approximately 60 percent of deaf students graduating from high school read at or below the fourth grade level.103 Low proficiency in reading and writing limits job opportunities and economic success.
In children, language impairment and delayed language acquisition are highly significant predictors of future academic, social, vocational, and adaptive outcomes.104-106 These impairments also tend to run in families,107 with converging evidence of genetic effects.108
Many communication disorders, such as specific language impairment (SLI) and autism spectrum disorder (ASD), first become apparent during early childhood when normal language acquisition takes place. One of the hallmarks of ASD is the diminished ability to communicate effectively—particularly in the expression and reception of language. NIDCD is committed to supporting research efforts to improve the diagnosis of ASD and SLI and to develop new, or improve existing, treatments of language deficits in children with ASD and SLI, especially school-aged children with ASD who remain non-verbal and school-aged children with SLI.
Occupational Voice Users
About three to nine percent of Americans have a voice disorder.109 Occupational voice users such as teachers, who represent one of the country’s largest employed groups, are particularly vulnerable. It is estimated that 11-38 percent of teachers have a voice problem on any given day,110-112 and cumulative estimates indicate nearly 60 percent of teachers have been affected over their working lives.110 Considering the impact of voice disorders for teachers—their diagnosis, treatment, and substitute teacher costs—the burden to the American economy is substantial, estimated to approach $3 billion annually in 1998.113
A 2009 study114 of seniors living independently showed that nearly one in five reported a voice problem, and about one in eight experienced difficulties in swallowing. These results demonstrated that severely affected individuals had reduced quality of life measures, even though only one in five of these individuals had sought treatment. Another study115 demonstrated that approximately 50 percent of seniors living independently had a hearing loss and they were significantly more likely to experience a voice problem. These studies demonstrate a need to simultaneously manage hearing loss and voice problems in older adults.
Stroke is a leading cause of adult disability in the United States.116 A significant proportion of stroke survivors have communication disorders (i.e., post-stroke aphasia) related to brain damage. The presence of such communication problems is a strong predictor of poor quality of life and decreased community participation.117 NIDCD supports research to understand the neurological bases of stroke-related language and swallowing deficits, the correlation of brain imaging data with prognosis, and the development of novel intervention strategies to improve outcomes.
The Voice, Speech, and Language Program
The NIDCD Voice and Speech Program performs and supports research to determine the nature, causes, treatment, and prevention of disorders of motor speech production throughout the lifespan. The Language Program is exploring the genetic bases of child speech and language disorders, as well as characterizing the linguistic and cognitive deficits in children and adults with language disorders. Both programs utilize a wide range of research approaches, including animal models of communication, to develop effective diagnostic and intervention strategies for people with voice, speech, or language impairments.