Age-Related Changes In Sound Intensity Encoding at the Cortex

About 50% of adults over the age of 75 have significant hearing loss. Since so many people experience hearing loss, it is important to understand how hearing changes with age. In our lab, we are examining how aging results in changes in auditory processing. My project determines the extent to which aging alters sound intensity encoding at the cortex. We hypothesized that age-related declines in the central auditory system, measured at the cortex, would result in degraded cortical responses and decreased sensitivity to sound intensity changes. We used electrophysiology to study how the brain processes sound in younger and older adults. Seven younger and six older normal-hearing adults heard 100 microsecond tonebursts with a frequency of 1000 Hz. Tones were presented in blocks of 500 trials each at 80, 90, and 100 dB and the N1P2 was recorded by a 64-electrode cap. P1 and N1 amplitudes were measured at each sound level and the slope of amplitude change by level was calculated. Results show that the responses from older adults are larger than those from younger adults. As sound intensity increased, the responses from both younger and older adults also increased. In conclusion, N1P2 cortical responses to large changes in sound intensity were more pronounced in older compared to younger adults, which was not what we expected. Preliminary results also suggest that hearing loss may affect the P1 amplitude in older adults. These results and further research will continue to provide a better understanding on how age affects hearing