Summary: Researchers report that subtle hearing loss in young adults may increase cognitive demands on the brain and could raise the risk of developing dementia later in life. The study found altered activity in the right frontal cortex among those with mild hearing decline.
Source: Ohio State University.
Turning up the volume on headphones or pushing for a front-row spot at concerts may do more than damage ears — it could change how the brain works.
New research from The Ohio State University indicates that even modest, unrecognized hearing loss in young adults can shift how the brain processes speech, recruiting brain regions normally engaged later in life. These changes may force the brain to use cognitive resources earlier than expected, a pattern that could have long-term consequences for thinking and memory.
“Even small hearing deficits can place extra demands on young people’s brains,” said lead researcher Yune Lee, an assistant professor of speech and hearing science at Ohio State. “That early burden could deplete resources that would otherwise be available later in life, and it raises concerns about a potential link to dementia.”
The study was published in the journal eNeuro.
Researchers examined healthy adults aged 18 to 41, using functional magnetic resonance imaging (fMRI) to measure brain activity while participants listened to spoken sentences. Sentences varied in syntactic complexity so the team could observe how the brain responds when comprehension becomes more challenging.
Before scanning, all participants reported normal hearing and completed audiometric testing. Although no one met clinical criteria for hearing impairment, some participants showed small differences in hearing acuity within the clinically normal range. Those subtle differences proved important.
When listening and comprehending sentences, most participants showed the expected left-lateralized activity in the brain regions typically responsible for language. However, participants with even modest hearing decline also showed increased activity in the right hemisphere, specifically in the right anterior middle frontal gyrus of the frontal cortex.
“This is not simply an ear problem — it’s a brain adaptation,” Lee explained. “Normally, healthy young adults rely heavily on left-hemisphere systems for language. In participants with mild hearing decline, the right frontal cortex was recruited as well, a pattern we usually see only in older adults.”
As people age, it is common to see more bilateral or right-hemisphere involvement in language tasks. The new finding is that this compensatory pattern can appear much earlier when hearing acuity is reduced, even slightly. The right frontal activity appeared to reflect the engagement of executive attention systems to cope with acoustic challenges, regardless of sentence complexity.
Researchers caution that the long-term consequences of this early compensatory recruitment are not yet known. One concern is that consistently using additional cognitive resources to understand everyday speech could accelerate cognitive wear and reduce reserve, potentially contributing to declines in memory and thinking over time.
Lee noted prior epidemiological research linking hearing loss to dementia risk: people with mild hearing loss have shown higher rates of cognitive decline, and those with moderate to severe loss face even greater risk. He suggested that increased listening effort may be one pathway connecting hearing changes to later cognitive problems.
“If your brain spends extra effort processing everyday sounds for decades, that may come at a cognitive cost,” Lee said. “Protecting hearing early in life could help preserve cognitive resources later on.”
The researchers advise young people to take hearing health seriously. Routine exposures such as prolonged use of personal music players at high volume and frequent attendance at loud live events can contribute to small, cumulative changes in hearing. Early attention to safe listening practices and hearing protection may reduce the need for the brain to compensate prematurely.
“Letting this process start in your 20s or 30s is like spending your retirement savings early,” Lee said. “You’re using resources you’ll want later in life.”
Source: Yune Lee — Ohio State University
Publisher: NeuroscienceNews.com (organizing summary)
Image Source: Public domain image provided with the original report.
Original Research: “Differences in Hearing Acuity among ‘Normal-Hearing’ Young Adults Modulate the Neural Basis for Speech Comprehension” by Yune S. Lee, Arthur Wingfield, Nam-Eun Min, Ethan Kotloff, Murray Grossman and Jonathan E. Peelle. Published in eNeuro, May 21, 2018. DOI: 10.1523/ENEURO.0263-17.2018
MLA: Ohio State University. “Subtle Hearing Loss While Young Alters Brain Function.” NeuroscienceNews, 22 May 2018.
APA: Ohio State University (2018, May 22). Subtle Hearing Loss While Young Alters Brain Function. NeuroscienceNews.
Chicago: Ohio State University. “Subtle Hearing Loss While Young Alters Brain Function.” NeuroscienceNews, May 22, 2018.
Abstract
Differences in Hearing Acuity among “Normal-Hearing” Young Adults Modulate the Neural Basis for Speech Comprehension
This study examines how modest variations in hearing ability affect the neural systems that support spoken sentence comprehension in young adults. Understanding spoken sentences requires both accurate perception of acoustic signals and linguistic processing to extract meaning. We used fMRI to measure brain activity while adults aged 18–41 listened to sentences that varied in syntactic complexity (subject-relative versus object-relative center-embedded clauses). All participants reported normal hearing and passed standard audiometric testing, though some showed small differences in hearing acuity within the clinically normal range.
Across participants, sentence processing primarily engaged a left-lateralized frontotemporal language network. Errors in comprehension, though infrequent, were associated with increased activity in bilateral cingulo-opercular and frontoparietal attention networks. Crucially, a whole-brain regression revealed that activity in the right anterior middle frontal gyrus (aMFG), part of the frontoparietal attention system, scaled with individual differences in hearing acuity: listeners with poorer hearing showed greater recruitment of this right frontal region when they successfully understood sentences. This right aMFG activity did not vary with sentence type, suggesting a general executive attention mechanism that responds to acoustic challenge independent of linguistic complexity. The results indicate that even modest declines in hearing can alter the neural systems supporting auditory sentence comprehension, requiring coordination between left perisylvian language systems and executive attention networks sensitive to acoustic difficulty.
Significance Statement
Hearing loss increases cognitive demand during speech comprehension. Using fMRI, we found that regions of the right frontal cortex, outside the traditional perisylvian language network, are more active in listeners with poorer hearing as measured by pure-tone thresholds. These results demonstrate that executive attention recruitment varies with hearing ability even in individuals without clinical hearing loss, highlighting how small acoustic deficits can change brain function during successful spoken language comprehension.