title: Evidence of altered corticomotor system connectivity in early-stage Alzheimer's disease.
abstract: OBJECTIVE
  There is increasing evidence for subtle motor dysfunction early in Alzheimer disease (AD), including common motor behaviors that were once considered unaffected early in the disease process. Our objective was to assess whether functional neural networks underlying motor behavior are altered by AD.
  
  
  METHODS
  We investigated AD-related differences in regional brain activation during motor performance. Nine older adults with early-stage AD and 10 without dementia underwent functional magnetic resonance imaging while performing a visually directed simple motor task (hand squeeze).
  
  
  RESULTS
  Despite some similarity in brain activation during motor performance, we found that individuals without dementia exhibited greater activation in accessory motor regions, supplementary motor area, and cerebellum compared with those with AD. We also assessed disease-related differences in regions where activity was functionally integrated with primary motor cortex. Using a psychophysiological interaction analysis, we found that those with AD displayed increased coactivation with primary motor cortex of bilateral motor and visual regions.
  
  
  CONCLUSIONS
  These AD-related differences in regional coactivation during motor execution may represent inefficiency in the motor network as a consequence of the disease process. Alternatively, they may represent compensatory activation. These findings provide further evidence that in early stages of AD, neuromotor function is altered even during simple motor behaviors. The results may have implications for performance of more complex tasks and may be associated with the well-characterized decline in dual-task performance in those with AD.
authors.affiliation: Department of Neurology, University of Kansas Medical Center, Kansas City, KS 66160, USA. evidoni@kumc.edu
authors.forename: Eric D
authors.initials: ED
authors.lastname: Vidoni
authors.forename: George P
authors.initials: GP
authors.lastname: Thomas
authors.forename: Robyn A
authors.initials: RA
authors.lastname: Honea
authors.forename: Natalia
authors.initials: N
authors.lastname: Loskutova
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Burns
mesh_terms: D000367:Age Factors; D000368:Aged; D000544:Alzheimer Disease / Q000175:diagnosis* / Q000534:rehabilitation; D000704:Analysis of Variance; D001931:Brain Mapping / Q000379:methods; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000473:pathology* / Q000502:physiology; D009048:Motor Skills / Q000502:physiology; D009434:Neural Pathways / Q000473:pathology / Q000503:physiopathology; D011379:Prognosis; D011597:Psychomotor Performance / Q000502:physiology*; D012016:Reference Values; D018570:Risk Assessment; D012720:Severity of Illness Index; D012737:Sex Factors; D013647:Task Performance and Analysis