It’s Not Your Ears, It’s Your Brain (UMD release):
“Could you repeat that?” The reason you may have to say something twice when talking to older family members at Thanksgiving dinner may not be because of their hearing. Researchers at the University of Maryland have determined that something is going on in the brains of typical older adults that causes them to struggle to follow speech amidst background noise, even when their hearing would be considered normal on a clinical assessment.
In an interdisciplinary study published by the Journal of Neurophysiology, researchers Samira Anderson, Jonathan Z. Simon, and Alessandro Presacco found that adults aged 61–73 with normal hearing scored significantly worse on speech understanding in noisy environments than adults aged 18–30 with normal hearing.”
Study: Evidence of degraded representation of speech in noise, in the aging midbrain and cortex (Journal of Neurophysiology)
- Abstract: Humans have a remarkable ability to track and understand speech in unfavorable conditions, such as in background noise, but speech understanding in noise does deteriorate with age. Results from several studies have shown that in younger adults, low frequency auditory cortical activity reliably synchronizes to the speech envelope, even when the background noise is considerably louder than the speech signal. However, cortical speech processing may be limited by age-related decreases in the precision of neural synchronization in the midbrain. To better understand the neural mechanisms contributing to impaired speech perception in older adults, we investigated how aging affects midbrain and cortical encoding of speech when presented in quiet and in the presence of a single competing talker. Our results suggest that central auditory temporal processing deficits in older adults manifest in both the midbrain and in the cortex. Specifically, midbrain frequency following responses to a speech syllable are more degraded in noise in older adults than in younger adults. This suggests a failure of the midbrain auditory mechanisms needed to compensate for the presence of a competing talker. Similarly, in cortical responses, older adults show larger reductions than younger adults in their ability to encode the speech envelope when a competing talker is added. Interestingly, older adults showed an exaggerated cortical representation of speech in both quiet and noise conditions, suggesting a possible imbalance between inhibitory and excitatory processes, or diminished network connectivity, that may impair their ability to efficiently encode speech.