Joseph W. Hall, PhD, is presently the principal investigator on two R01 NIH research grants, both funded by the National Institute of Deafness and other Communication Disorders. One of these projects is Development and Plasticity in Normal and Impaired Hearing. The main experiment in this project is investigating the effect of sensorineural hearing loss on the development of hearing in children. The aim is to examine the ability of these children to obtain benefit for speech perception in noise for noise that has spectral dips, temporal dips, or both spectral and temporal dips. The ability to benefit from such spectro-temporal dips probably accounts for the relatively good ability of listeners with normal hearing to understand speech in noisy environments. It is important to assess the effect of hearing loss on these abilities, particularly in children, where experience with speech/language cues is relatively limited.
A second experiment in this NIH grant is investigating the development of auditory temporal processing in normal-hearing children. The specific focus is on the ability to use very brief temporal cues and to separate these cues from other temporally proximal acoustical information. The results of this study should aid the understanding of the ability to understand speech in difficult listening situations. The lead investigator on this project is our postdoctoral fellow, Shuman He.
A third study in this NIH grant is investigating the ability of children to integrate speech information that arises from distinctly different frequency regions. This kind of ability is crucial for successful performance in children with cochlear implants. Results from this study are suggesting that children are as good as adults in integrating information across frequency, but that children require more frequency detail than adults to achieve a criterion level of speech recognition performance. This project is being carried out by fourth year medical student, Stefan Mlot.
Dr. Hall’s second NIH-funded grant is Spectro-temporal Processing in Normal and Impaired Ears. One series of studies in this project is investigating the ability of patients with sensorineural hearing loss to integrate information in one spectral region at a given time with information in other spectral regions at a later time. This ability is probably quite useful in understanding speech when listening conditions are very poor, and a limitation in this capacity could account for part of the difficulty experienced by hearing-impaired patients in background noise. The project is also investigating central auditory processes that enable the perception of signals in fluctuating background noises. Many natural background sounds possess such fluctuations, and it appears as though auditory processes have developed that take advantage of the favorable listening intervals that occur in the fluctuation minima. These studies should lead to a better understanding of the factors that enable us to hear in background noise.
Dr. Hall is also a co-investigator on an NIH grant that is investigating changes in brain anatomy and function that may accompany sensori-neural hearing loss in humans. This project uses both standard psychoacoustical methods and functional magnetic resonance imaging (FMRI) techniques. The approach is currently focusing on patients who have very steeply sloping hearing losses in one ear. Preliminary data suggest that it is possible the central auditory system reorganizes in such a way that greater weight is placed on the output of the better ear in such patients, even for frequencies at which hearing is normal in both ears. The results of this study will have implications for the ways in which brain function and structure change in response to peripheral hearing loss.