Your Brain, Not Your Ears May Be Causing Your Hearing Impairment
Researchers at the University of Maryland have found that something is happening in the brain of older adults that usually causes them to have a hard time following speech, especially when they are in the middle of a noisy background. This happens even though they're hearing is considered normal during a routine clinical assessment.
According to Times of India, the study involving three researchers, Samira Anderson, Jonathan Z. Simon, and Alessandro Presacco, found that adults aged 61-73 years old with normal hearing got a significantly low score on speech understanding in noisy areas compared to adults aged 18-30 with normal hearing.
The researchers, who are involved with UMD's Brain and Behavior Initiative, explained: "Evidence of degraded representation of speech in noise, in the aging midbrain and cortex" is part of an 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.
The study, published in the Journal of Neurophysiology, is a combination of different fields of hearing and speech science, neuroscience and cognitive science, electrical engineering, biology, and systems science. As reported by The Economic Times, the participants of the study had to go through 2 different kinds of scans to gauge their brain's electrical activity while they listened to people talk. The researchers were able to see what the subjects' brains doing when they were asked what someone was saying, both in a quiet environment and amidst a level of noise.
They analyzed two areas of the brain, the more 'ancestral' midbrain area, which most vertebrate animals, all the way down to fish have, which usually 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. The researchers found that in the younger group subject, the midbrain created a signal that matched its task in each case, looking like speech in the quiet environment and speech clearly recognizable against a noisy background in the noise environment.
However, BC Post reported that when researchers looked at the older group, they found that the quality of the response to the signal has lessened in a quiet environment, and had an even worse response in a noisy environment. "For older listeners, even when there isn't any noise, the brain is already having trouble processing the speech," said researcher Simon.
Neural signals recorded from cortex showed that younger adults are able to process speech well in a relatively short amount of time; however the auditory cortex of older test subjects took longer to break down the same amount of information. "Part of the comprehension problems experienced by older adults in both quiet and noise conditions could be linked to age-related imbalance between excitatory and inhibitory neural processes in the brain," researcher Presacco said. "This imbalance could impair the brain's ability to correctly process auditory stimuli and could be the main cause of the abnormally high cortical response observed in our study."
"Often we will hear an older person say, 'I can hear you, I just can't understand you,'" said Anderson. "This research gives us new insight into why that is the case." Meanwhile, experts said taht tThe deterioration of brain function usually happens to older adults and a natural part of the aging process. Researchers are now looking into whether brain training techniques may be able to help older adults improve their speech comprehension.