READ MOREResearchers 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.
The researchers are all associated with the UMD's Brain and Behavior Initiative.
"Evidence of degraded representation of speech in noise, in the aging midbrain and cortex" is part of ongoing research into the so-called cocktail party problem, or the brain's ability to focus on and process a particular stream of speech in the middle of a noisy environment.
This research brings together the fields of hearing and speech science, neuroscience and cognitive science, electrical engineering, biology, and systems science.
The study subjects underwent two different kinds of scans to measure their brains' electrical activity while they listened to people talk. The researchers were able to see what the subjects' brains were up to when asked what someone was saying, both in a quiet environment and amidst a level of noise.
The researchers studied two areas of the brain. They looked at the more 'ancestral' midbrain area, which most vertebrate animals -- all the way down to fish - have, and which does basic processing of all sounds. They also looked at the cortex, which is particularly large in humans and part of which specializes in speech processing.
In the younger subject group, the midbrain generated a signal that matched its task in each case - looking like speech in the quiet environment, and speech clearly discernable against a noisy background in the noise environment.
But in the older subject group, the quality of the response to the speech signal was degraded even when in the quiet environment, and the response was even worse in the noisy environment.
"For older listeners, even when there isn't any noise, the brain is already having trouble processing the speech," said Simon. ■