PP1011 - Effects of Aging on the Human Auditory Cortex: A Functional Near-Infrared Spectroscopy (fNIRS) Study

Abstract:
This study examines aging effects on the human auditory cortex. Young (18-30 years, n=10) and Older (>60 years, n=10) adults with normal hearing sensitivity will be tested with functional near-infrared spectroscopy (fNIRS); the Speech, Spatial and Qualities of Hearing Scale (SSQ); and behavioral tests of sound perception. fNIRS responses will be recorded during passive listening to speech stimuli and babble noise. Data collection and analysis will be completed by February 2025. It is expected that all behavioral measures will be poorer in the Older group vs. the Young group and there is a correlation between fNIRS responses and other measures.

Summary:
Rationale
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). In older adults with clinically defined “normal hearing” based on hearing sensitivity, the auditory system may go through neurological changes, which can only be detected by more advanced and sophisticated assessments than clinical assessments. It is necessary to using state-of-the art neuroimaging techniques to understand aging effects on the auditory system without influence from possible hearing loss in older adults in order to identify early signs of aging effects in order to use appropriate treatment approaches (e.g., training the brain) to reverse aging effects.

The current study will examine aging effects on human auditory cortex using functional near-infrared spectroscopy (fNIRS). fNIRS is a neuroimaging technique that uses infrared light to measure cortical hemoglobin oxygenation changes related to brain activities. There are only a few fNIRS studies that have focused on aging effects on the auditory functions. More such studies are needed for a better understanding of how aging effects the human auditory system.

Method
We will recruit two groups of participants: young (18-30 years of age) and older (>60 years) healthy adults with normal hearing. All participants will be tested with 1) the Speech, Spatial and Qualities of Hearing Scale (SSQ) that assesses subjective hearing abilities in daily-life listening situations, 2) behavioral testing of speech perception, and 3) fNIRS testing using speech stimuli and babble noise to measure cortical responses in the temporal and frontal lobes. For data analysis, the effect of Subject Group (Young vs. Older), Stimulus type (Speech vs. Noise) on all outcomes (fNIRS measures such as oxygenated hemoglobin levels, SSQ scores, and percent correct in speech perception tasks) will be examined using the mixed design two-way ANOVA. Correlations between fNIRS measures and other measures will be assessed with the linear correlation analysis.

Results
Data collection and analysis are ongoing and will be completed by February 2025. We expect that, compared to the Young group, the Older group will show poorer SSQ scores, behavioral performance of speech perception, and decreased oxygenated hemoglobin levels for speech stimuli. It is also expected that there is a correlation between the oxygenated hemoglobin levels in the temporal lobe when listening to speech stimuli and other measures.

Conclusion
fNIRS measures may be a useful noninvasive measure to demonstrate aging effects on the auditory system.