The long-term goal of this proposed research plan is to understand how aging affects the representation of frequency in the human auditory system. Age-related declines in processing of temporal and spectral information may contribute to decreased speech perception, even among older adults whose hearing sensitivity can be described as falling within clinical normal limits. These declines in the auditory system are thought to be, in part, related to how central auditory nervous system represents or encodes acoustic characteristics of sounds, such as frequency. The proposed experiment will use behavioral and physiological measures to evaluate age-related changes in the processing of spectral information, using a within-subjects design. In addition, the relationship between perceptual and physiologic measures will be examined. The first specific aim is to characterize the effects of age on the ability to perceive small changes in frequency. Behavioral frequency discrimination difference limens (FDLs) will be obtained at 500 and 1000 Hz. The second specific aim is to characterize the effects of age on the neural representation of frequency, as measured with the frequency-following response (FFR). The FFR is an auditory evoked potential that is sensitive to the spectral content of stimuli. FFRs will be obtained at 500 and 1000 Hz from the same participants that FDLs were obtained from to address specific aim one. The third specific aim is to determine the effects of age on the relationship between the perception and neural representation of age. The data from experiments addressing aims one and two will be analyzed to determine the relationship between the perceptual and physiological measures, as well as the effects of age on this relationship. From a basic science perspective, the proposed research will help define the biological process of aging on the perception and neural representation of frequency. From a clinical perspective, information gained from the proposed research plan may help to improve approaches to aural rehabilitation of adults with hearing loss.
Older adults, even with clinically normal hearing, have difficulty understanding speech for reasons that are not well understood. This research will examine changes in listening abilities and brain activity that occur with aging. Information learned from this research may help to develop effective training programs help older adults with hearing loss understand speech better.
