title: Executive functions in mild cognitive impairment: emergence and breakdown of neural plasticity.
abstract: BACKGROUND
  Our goal was to test the effect of disease severity on the brain activation associated with two executive processes: manipulation and divided attention.
  
  
  METHODS
  This was achieved by administrating a manipulation task and a divided attention task using functional magnetic resonance imaging to 24 individuals with mild cognitive impairment (MCI) and 14 healthy controls matched for age, sex and education. The Mattis Dementia Rating Scale was used to divide persons with MCI into those with better and worse cognitive performances.
  
  
  RESULTS
  Both tasks were associated with more brain activation in the MCI group with higher cognition than in healthy controls, particularly in the left frontal areas. Correlational analyses indicated that greater activation in a frontostriatal network hyperactivated by the higher-cognition group was related with better task performance, suggesting that these activations may support functional reorganization of a compensatory nature. By contrast, the lower-cognition group failed to show greater cerebral hyperactivation than controls during the divided attention task and, during the manipulation task, and showed less brain activation than controls in the left ventrolateral cortex, a region commonly hypoactivated in patients with Alzheimer's disease.
  
  
  CONCLUSIONS
  These findings indicate that, during the early phase of MCI, executive functioning benefits from neural reorganization, but that a breakdown of this brain plasticity characterizes the late stages of MCI.
authors: Centre de recherche de l'Institut universitaire de gériatrie de Montréal, Montréal, Canada.
authors: Francis
authors: F
authors: Clément
authors: Serge
authors: S
authors: Gauthier
authors: Sylvie
authors: S
authors: Belleville
mesh_terms: D000368:Aged; D001931:Brain Mapping; D060825:Cognitive Dysfunction / Q000503:physiopathology*; D056344:Executive Function / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009473:Neuronal Plasticity / Q000502:physiology*; D009483:Neuropsychological Tests