Hearing impairment is a common feature of old age. Human temporal bones from old individuals with hearing impairment show the loss of sensory and neural cells within the cochlea as well as vascular changes, strial atrophy and thickening of the basilar membrane. These changes certainly contribute to hearing impairment, however there is also evidence that the surviving neural elements of the cochlea may be abnormal. Changes in the structure and function of the surviving neurons may play as important a role in the hearing impairment associated with aging as actual cell loss. Animal models of aging have also shown the loss of sensory and neural cells within the cochlea and brainstem and atrophy of the stria vascularis in old animals. Using the rat, the present proposal will investigate the morphology and function of the surviving neural cells which project from the cochlea to the brainstem. Morphological studies will include descriptions of the peripheral and central processes of the spiral ganglion cells as seen following labeling with horseradish peroxidase. Electro-physiological studies will include recording the spontaneous and stimulus- evoked activity of the spiral ganglion cells with microelectrodes. The function of the spiral ganglion cells will also be evaluated using the 2-deoxy D-(14C)-glucose technique. Evaluation of the results of these experiments will allow us to determine whether, and in what way the information transmission function of the aging auditory nerve is compromised. These results will have implications for the development of hearing aids and cochlear implants for the elderly.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
First Independent Research Support & Transition (FIRST) Awards (R29)
Project #
1R29NS024690-01
Application #
3476786
Study Section
Hearing Research Study Section (HAR)
Project Start
1987-04-01
Project End
1992-03-31
Budget Start
1987-04-01
Budget End
1988-03-31
Support Year
1
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of California San Diego
Department
Type
Schools of Medicine
DUNS #
077758407
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Keithley, E M; Croskrey, K L (1990) Spiral ganglion cell endings in the cochlear nucleus of young and old rats. Hear Res 49:169-77
Keithley, E M; Ryan, A F; Woolf, N K (1989) Spiral ganglion cell density in young and old gerbils. Hear Res 38:125-33
Ryan, A F; Furlow, Z; Woolf, N K et al. (1988) The spatial representation of frequency in the rat dorsal cochlear nucleus and inferior colliculus. Hear Res 36:181-9