title: Age and amyloid-related alterations in default network habituation to stimulus repetition.
abstract: The neural networks supporting encoding of new information are thought to decline with age, although mnemonic techniques such as repetition may enhance performance in older individuals. Accumulation of amyloid-β, one hallmark pathology of Alzheimer's disease (AD), may contribute to functional alterations in memory networks measured with functional magnetic resonance imaging (fMRI) prior to onset of cognitive impairment. We investigated the effects of age and amyloid burden on fMRI activity in the default network and hippocampus during repetitive encoding. Older individuals, particularly those with high amyloid burden, demonstrated decreased task-induced deactivation in the posteromedial cortices during initial stimulus presentation and failed to modulate fMRI activity in response to repeated trials, whereas young subjects demonstrated a stepwise decrease in deactivation with repetition. The hippocampus demonstrated similar patterns across the groups, showing task-induced activity that decreased in response to repetition. These findings demonstrate that age and amyloid have dissociable functional effects on specific nodes within a distributed memory network, and suggest that functional brain changes may begin far in advance of symptomatic Alzheimer's disease.
authors.affiliation: Athinoula A. Martinos Center for Biomedical Imaging, Department of Psychiatry, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA. patrizia@nmr.mgh.harvard.edu
authors.forename: Patrizia
authors.initials: P
authors.lastname: Vannini
authors.forename: Trey
authors.initials: T
authors.lastname: Hedden
authors.forename: John A
authors.initials: JA
authors.lastname: Becker
authors.forename: Caroline
authors.initials: C
authors.lastname: Sullivan
authors.forename: Deepti
authors.initials: D
authors.lastname: Putcha
authors.forename: Dorene
authors.initials: D
authors.lastname: Rentz
authors.forename: Keith A
authors.initials: KA
authors.lastname: Johnson
authors.forename: Reisa A
authors.initials: RA
authors.lastname: Sperling
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology* / Q000502:physiology; D005260:Female; D006185:Habituation, Psychophysiologic / Q000502:physiology; D006801:Humans; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009415:Nerve Net / Q000473:pathology* / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D058225:Plaque, Amyloid / Q000473:pathology*; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D055815:Young Adult