Does hearing loss change how the aging auditory cortex connects?
Among older adults, worse hearing went with stronger resting connectivity between the right auditory cortex and an attention-control region, while age itself showed no such link once hearing was accounted for.
Source
Functional Connectivity of Heschl's Gyrus Associated With Age-Related Hearing Loss: A Resting-State fMRI Study
Study at a glance
- Design
- Cross-sectional — Single-group correlational resting-state fMRI: seed-to-voxel connectivity from left and right Heschl's gyrus correlated with audiometric hearing thresholds, controlling for age, working memory and processing speed
- N
- N=31 · 31 older adults scanned once; follow-up analyses re-run without the five hearing-aid users
- Population
- Community-dwelling older adults aged 60-80 in the Phoenix area, native English speakers, right-handed, without dementia
- Outcome
- Voxelwise functional connectivity from left and right Heschl's gyrus and its correlation with pure-tone hearing thresholds (all frequencies, speech frequencies, high frequencies, each ear)
Structured fields used in claim comparison tables when every cited study has a complete layer.
What they did
Thirty-one healthy older adults had their hearing measured with pure-tone audiometry, completed working-memory and processing-speed subtests of an IQ battery, and lay quietly in an MRI scanner for a 10-minute resting-state scan. The researchers correlated the activity of left and right Heschl's gyrus (primary auditory cortex) with every other brain voxel, then asked whether those connectivity maps varied with hearing thresholds after controlling for age and cognition, and vice versa.
What they found
Both auditory cortices were functionally connected to auditory, sensorimotor and visual cortex and to the cingulo-opercular attention network. Greater hearing loss predicted stronger connectivity from right Heschl's gyrus to the dorsal anterior cingulate and supplementary motor area; this was driven by speech-frequency loss and by the left ear, and held without the hearing-aid users. Age, working memory and processing speed showed no significant connectivity correlations once hearing was controlled, and left Heschl's gyrus connectivity was unrelated to hearing.
The limits
What it doesn't show
It is a small, correlational, single-time-point study, so it cannot show that hearing loss causes the connectivity change or that the change is compensatory; that interpretation is the authors' hypothesis. Participants ranged only from normal hearing to moderate loss, were mostly women and highly educated, and the authors note that more power is needed. No listening task or listening-effort measure was collected, so the link to attention during real listening is inferred from other studies.
Key terms
- Heschl's gyrus
- A ridge on the upper surface of the temporal lobe that contains primary auditory cortex, the first cortical stop for sound information.
- Resting-state functional connectivity
- How strongly the slow, spontaneous activity of two brain regions rises and falls together while a person lies in the scanner doing no task.
- Cingulo-opercular network
- A set of regions including the dorsal anterior cingulate and insula thought to maintain task goals and control attention.
- Pure-tone audiometry
- A hearing test that finds the quietest tone a person can detect at each frequency; higher thresholds mean worse hearing.
- Seed-to-voxel analysis
- Taking the average signal of one chosen region (the seed) and correlating it with the signal of every other point in the brain.
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Quiz yourself
What brain structure served as the seed region in this study?
Common questions
Why not simply compare older adults with and without hearing loss?
Age-related hearing loss lies on a continuum and most older adults sit in the mild-to-moderate middle, so the authors treated hearing as a continuous variable within one group rather than splitting people into arbitrary groups.
Why does the left ear relate to the right auditory cortex?
Auditory pathways cross, so each ear projects most strongly to the opposite hemisphere; the finding that left-ear loss tracked right Heschl's gyrus connectivity fits that anatomy.
Does this mean aging studies have been wrong?
Not necessarily wrong, but the authors argue that aging fMRI studies rarely measure hearing, so some effects credited to age could partly reflect hearing loss.
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