Abstract:

Aging results in declines in all nervous systems, including the auditory system, causing clinical symptoms (e.g., difficulties in understanding speech, especially in noisy environments, a task that requires the ability of the auditory system to separate sounds with different features, such as frequencies). The auditory system may go through neurological changes in older adults with clinically defined “normal hearing” based on hearing sensitivity shown in audiometry. The aim of this study is to use functional near-infrared spectroscopy (fNIRS), a non-invasive optical neuroimaging technique, to examine auditory cortex activation in pre-older adults (e.g., 50-60 years of age) to identify early neurophysiological signs of aging effects for diagnostic and intervention purposes. The fNIRS measures cortical hemoglobin oxygenation related to brain activities with a better temporal resolution than the functional magnetic resonance imaging (fMRI) technique and a better spatial resolution than the electroencephalography (EEG). There are only a few fNIRS studies that have examined the effects of aging on auditory functions. More such studies are needed to determine early fNIRS signs of aging.

Two groups of participants were included: Young (18-30 years of age) and pre-older (50-60 years) healthy adults with normal hearing confirmed by clinical pure-tone audiometry. All participants were tested with 1) self-assessed hearing abilities using the Speech, Spatial, and Qualities of Hearing Scale (SSQ) questionnaire, 2) behavioral testing of speech perception and sound frequency selectivity, and 3) fNIRS responses to speech stimuli and babble noise.

Data collection and analysis are ongoing and will be completed by April 2025. For data analysis, the effect of Subject Group (Young vs. pre-Older), Stimulus type (Speech vs. Babble noise) on all outcomes (fNIRS measures such as oxygenated hemoglobin, and deoxygenated hemoglobin levels, SSQ scores, and percent correct in speech and the value of frequency selectivity) will be examined using the mixed design two-way ANOVA. We expect that, compared to the Young group, the pre-Older group will show poorer SSQ scores, behavioural performance of sound perception, and auditory cortex.