title: Prognostic value of posteromedial cortex deactivation in mild cognitive impairment.
abstract: BACKGROUND
  Normal subjects deactivate specific brain regions, notably the posteromedial cortex (PMC), during many tasks. Recent cross-sectional functional magnetic resonance imaging (fMRI) data suggests that deactivation during memory tasks is impaired in Alzheimer's disease (AD). The goal of this study was to prospectively determine the prognostic significance of PMC deactivation in mild cognitive impairment (MCI).
  
  
  RESULTS
  75 subjects (34 MCI, 13 AD subjects and 28 controls) underwent baseline fMRI scanning during encoding of novel and familiar face-name pairs. MCI subjects were followed longitudinally to determine conversion to AD. Regression and analysis of covariance models were used to assess the effect of PMC activation/deactivation on conversion to dementia as well as in the longitudinal change in dementia measures. At longitudinal follow up of up to 3.5 years (mean 2.5+/-0.79 years), 11 MCI subjects converted to AD. The proportion of deactivators was significantly different across all groups: controls (79%), MCI-Nonconverters (73%), MCI-converters (45%), and AD (23%) (p<0.05). Mean PMC activation magnitude parameter estimates, at baseline, were negative in the control (-0.57+/-0.12) and MCI-Nonconverter (-0.33+/-0.14) groups, and positive in the MCI-Converter (0.37+/-0.40) and AD (0.92+/-0.30) groups. The effect of diagnosis on PMC deactivation remained significant after adjusting for age, education and baseline Mini-Mental State Exam (p<0.05). Baseline PMC activation magnitude was correlated with change in dementia ratings from baseline.
  
  
  CONCLUSIONS
  Loss of physiological functional deactivation in the PMC may have prognostic value in preclinical AD, and could aid in profiling subgroups of MCI subjects at greatest risk for progressive cognitive decline.
authors.affiliation: Alzheimer Imaging Research Laboratory and Brain Imaging and Analysis Center, Department of Radiology, Duke University Medical Center, Durham, North Carolina, United States of America. petre001@mc.duke.edu
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Petrella
authors.forename: Steven E
authors.initials: SE
authors.lastname: Prince
authors.forename: Lihong
authors.initials: L
authors.lastname: Wang
authors.forename: Caroline
authors.initials: C
authors.lastname: Hellegers
authors.forename: P Murali
authors.initials: PM
authors.lastname: Doraiswamy
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000175:diagnosis / Q000473:pathology; D001921:Brain / Q000473:pathology; D016022:Case-Control Studies; D003072:Cognition Disorders / Q000175:diagnosis* / Q000473:pathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011379:Prognosis; D020651:Ventral Thalamic Nuclei / Q000473:pathology