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New Method to Test for Hearing Loss
Purdue University audiologist Karen Iler Kirk is working on a new technique to diagnose hearing loss in a way that more accurately reflects real-world situations.
"The goal of our research is to develop new tests that reflect more natural listening situations with visual cues and different background noises, voice quality, dialects, and speaking rates," Kirk explained. "This is a more accurate way to predict how people perceive speech in the real world and, therefore, can help us determine appropriate interventions, such as cochlear implants."
Funded by a $2.8 million grant from the National Institute on Deafness and Other Communication Disorders of the National Institutes of Health, the five-year project will develop two new audiovisual and multi-talker sentence tests that expand on traditional spoken-word recognition tests used since the 1950s. More than 1,000 people ages 4-65 will participate in the development of tests for adults and children.
The research will also expand word lists from traditional monosyllabic words to a greater range of words based on frequency of use and lexical density (the number of words phonetically similar to the target). The 10 diverse speakers, who are recording more than 6,000 sentences combined, will not produce perfectly articulated speech. The materials will be presented in auditory and visual formats, so listeners can simultaneously listen and speechread.
Participants will be tested in auditory-only, visual-only, or auditory-visual modalities. At the end of the project, DVDs containing the test as well as instruction booklets, data-gathering forms, and a manual for data interpretation will be available to professionals.
Mild Hearing Loss Affects Neurological Processes
Mild to moderate forms of hearing loss can have a lasting impact on the auditory cortex, according to findings by researchers at New York University’s Center for Neural Science.
Previously, researchers had been unable to determine conclusively the neurological impact of mild hearing loss, such as conductive losses that occur with childhood middle ear infections. The study sought to address this question in an animal model by measuring the impact of conductive hearing loss without injury to the cochlea.
The researchers induced conductive hearing loss in developing gerbils, and then measured the functionality of neural connections within the subjects’ auditory cortex. The results showed neural changes in auditory cortex following a brief period of hearing loss. Specifically, the synaptic response of the auditory neurons adapted more rapidly and to a greater extent. The researchers also found that auditory cortex neurons became more sensitive to stimulation.
The study, the first to show central effects of mild hearing loss, indicates that auditory cortex function is susceptible to relatively modest loss of hearing during development and suggests that perceptual deficits may be linked to alterations in the central nervous system. Visit the August 2007 issue of the Journal of Neuroscience to read an abstract of the study by Han Xu, Vibhakar Kotak, and Dan Sanes.
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