“Could you repeat that?” Study links hearing loss to brain aging

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hearing_brainIt’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.

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