title: Age-related effects on word recognition: reliance on cognitive control systems with structural declines in speech-responsive cortex.
abstract: Speech recognition can be difficult and effortful for older adults, even for those with normal hearing. Declining frontal lobe cognitive control has been hypothesized to cause age-related speech recognition problems. This study examined age-related changes in frontal lobe function for 15 clinically normal hearing adults (21-75 years) when they performed a word recognition task that was made challenging by decreasing word intelligibility. Although there were no age-related changes in word recognition, there were age-related changes in the degree of activity within left middle frontal gyrus (MFG) and anterior cingulate (ACC) regions during word recognition. Older adults engaged left MFG and ACC regions when words were most intelligible compared to younger adults who engaged these regions when words were least intelligible. Declining gray matter volume within temporal lobe regions responsive to word intelligibility significantly predicted left MFG activity, even after controlling for total gray matter volume, suggesting that declining structural integrity of brain regions responsive to speech leads to the recruitment of frontal regions when words are easily understood.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Avenue, MSC 550, Charleston, SC 29425-5500, USA. eckert@musc.edu
authors.forename: Mark A
authors.initials: MA
authors.lastname: Eckert
authors.forename: Adam
authors.initials: A
authors.lastname: Walczak
authors.forename: Jayne
authors.initials: J
authors.lastname: Ahlstrom
authors.forename: Stewart
authors.initials: S
authors.lastname: Denslow
authors.forename: Amy
authors.initials: A
authors.lastname: Horwitz
authors.forename: Judy R
authors.initials: JR
authors.lastname: Dubno
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D001288:Attention / Q000502:physiology; D001303:Auditory Cortex / Q000502:physiology*; D005260:Female; D006179:Gyrus Cinguli / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D021641:Recognition, Psychology / Q000502:physiology*; D013067:Speech Perception / Q000502:physiology*