title: Complexity and synchronicity of resting state blood oxygenation level-dependent (BOLD) functional MRI in normal aging and cognitive decline.
abstract: OBJECTIVE
  To explore the use of approximate entropy (ApEn) as an index of the complexity and the synchronicity of resting state blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) in normal aging and cognitive decline associated with familial Alzheimer's disease (fAD).
  
  
  METHODS
  Resting state BOLD fMRI data were acquired at 3T from two independent cohorts of subjects consisting of healthy young (age 23 ± 2 years, n = 8) and aged volunteers (age 66 ± 3 years, n = 8), as well as 22 fAD associated subjects (14 mutation carriers, age 41.2 ± 15.8 years; and eight nonmutation carrying family members, age 28.8 ± 5.9 years). Mean ApEn values were compared between the two age groups and correlated with cognitive performance in the fAD group. Cross-ApEn (C-ApEn) was further calculated to assess the asynchrony between precuneus and the rest of the brain.
  
  
  RESULTS
  Complexity of brain activity measured by mean ApEn in gray and white matter decreased with normal aging. In the fAD group, cognitive impairment was associated with decreased mean ApEn in gray matter as well as decreased regional ApEn in right precuneus, right lateral parietal regions, left precentral gyrus, and right paracentral gyrus. A pattern of asynchrony between BOLD fMRI series emerged from C-ApEn analysis, with significant regional anti-correlation with cross-correlation coefficient of functional connectivity analysis.
  
  
  CONCLUSIONS
  ApEn and C-ApEn may be useful for assessing the complexity and synchronicity of brain activity in normal aging and cognitive decline associated with neurodegenerative diseases.
authors.affiliation: Department of Neurology, University of California Los Angeles, Los Angeles, CA 90095, USA.
authors.forename: Collin Y
authors.initials: CY
authors.lastname: Liu
authors.forename: Anitha P
authors.initials: AP
authors.lastname: Krishnan
authors.forename: Lirong
authors.initials: L
authors.lastname: Yan
authors.forename: Robert X
authors.initials: RX
authors.lastname: Smith
authors.forename: Emily
authors.initials: E
authors.lastname: Kilroy
authors.forename: Jeffery R
authors.initials: JR
authors.lastname: Alger
authors.forename: John M
authors.initials: JM
authors.lastname: Ringman
authors.forename: Danny J J
authors.initials: DJ
authors.lastname: Wang
mesh_terms: D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000502:physiology*; D063132:Connectome / Q000379:methods; D003344:Cortical Synchronization / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009415:Nerve Net / Q000502:physiology*; D010100:Oxygen / Q000097:blood*; D055815:Young Adult
chemical_list: D010100:Oxygen