title: Posterior compensatory network in cognitively intact elders with hippocampal atrophy.
abstract: Functional compensation in late life is poorly understood but may be vital to understanding long-term cognitive trajectories. To study this we first established an empirically derived threshold to distinguish hippocampal atrophy in those with Mild Cognitive Impairment (MCI n = 34) from those with proficient cognition (PRO n = 22), using data from a population-based cohort. Next, to identify compensatory networks we compared cortical activity patterns during a graded spatial working memory (SWM) task in only cognitively proficient individuals, either with (PROATR ) or without hippocampal atrophy (PRONIL ). Multivariate Partial Least Squares analyses revealed that these groups engaged spatially distinct SWM-related networks. In those with hippocampal atrophy and under conditions of basic-SWM demand, expression of a posterior compensatory network (PCN) comprised calcarine and posterior parietal cortex strongly correlated with superior SWM performance (r = -0.96). In these individuals, basic level SWM response times were faster and no less accurate than in those with no hippocampal atrophy. Cognitively proficient older individuals with hippocampal atrophy may, therefore, uniquely engage posterior brain areas when performing simple spatial working memory tasks.
authors.affiliation: Regenerative Neuroscience Group, Brain & Mind Research Institute, University of Sydney, Sydney, Australia; School of Medical Sciences, Sydney Medical School, University of Sydney, Sydney, Australia.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Valenzuela
authors.forename: Andrew J F
authors.initials: AJ
authors.lastname: Turner
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Kochan
authors.forename: Wei
authors.initials: W
authors.lastname: Wen
authors.forename: Chao
authors.initials: C
authors.lastname: Suo
authors.forename: Harry
authors.initials: H
authors.lastname: Hallock
authors.forename: Randy A
authors.initials: RA
authors.lastname: McIntosh
authors.forename: Perminder
authors.initials: P
authors.lastname: Sachdev
authors.forename: Michael
authors.initials: M
authors.lastname: Breakspear
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001284:Atrophy; D001931:Brain Mapping; D060825:Cognitive Dysfunction / Q000473:pathology*; D015331:Cohort Studies; D005260:Female; D006624:Hippocampus / Q000473:pathology* / Q000503:physiopathology*; D006801:Humans; D016018:Least-Squares Analysis; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D015999:Multivariate Analysis; D009434:Neural Pathways / Q000473:pathology / Q000503:physiopathology; D009483:Neuropsychological Tests; D009929:Organ Size; D010296:Parietal Lobe / Q000503:physiopathology; D012815:Signal Processing, Computer-Assisted; D065852:Spatial Memory / Q000502:physiology*
keywords: compensation; functional MRI; hippocampus; mild cognitive impairment; working memory