Hearing loss is one of the most common chronic health conditions in older adults that affects 90 per cent of seniors who are over 80 years old. Older adults even with clinically normal hearing often experience different levels of difficulties in understanding conversations in noisy environments. However, how older brains process speech sounds under the challenges of impoverished hearing and declined auditory processing ability remains unclear.

As people age, their periphery and central auditory systems (areas of the brain that help to intake and interpret sounds) decline in functions and plugging into other parts of the brain is needed as a means of compensation. A brain imaging study conducted by Dr. DU Yi from the Institute of Psychology of Chinese Academy of Sciences and her collaborators from the Rotman Research Institute at Baycrest and University of Toronto has pinpointed speech motor areas in the frontal lobe of the brain that older adults rely on to differentiate speech sounds in background noise, which could revolutionize the treatment of hearing loss.

The study analyzed the brain activity measured with functional magnetic resonance imaging (fMRI) of 16 young and 16 older adults when they identified syllables, while the level of noise changed in the background. The researchers found that compared to young adults, older adults had stronger activation in speech motor areas, brain regions that are important for speech articulation and production, which was associated with improved speech discrimination performance in older adults.

Using a machine learning method called multivariate pattern classification, they also showed preserved specificity of speech representations in speech motor areas but not in auditory cortices in older adults’ brain.

The findings suggest that to compensate for hearing loss, older adults increasingly engage in the speech motor areas and use the articulatory prediction information to interpret someone’s talking in a noisy room. By showing there are other brain areas affecting hearing, researchers can design training programs targeting these brain areas to see if people can improve their use.

This study was published in Nature Communications. It was support by Canadian Institutes of Health Research.