title: A study of structural and functional connectivity in early Alzheimer's disease using rest fMRI and diffusion tensor imaging.
abstract: OBJECTIVE
  Alzheimer's disease (AD) is a progressive neurodegenerative condition where in early diagnosis and interventions are key policy priorities in dementia services and research. We studied the functional and structural connectivity in mild AD to determine the nature of connectivity changes that coexist with neurocognitive deficits in the early stages of AD.
  
  
  METHODS
  Fifteen mild AD subjects and 15 cognitively healthy controls (CHc) matched for age and gender, underwent detailed neurocognitive assessment and magnetic resonance imaging (MRI) of resting state functional MRI (rs-fMRI) and diffusion tensor imaging (DTI). Rest fMRI was analyzed using dual regression approach and DTI by voxel wise statistics.
  
  
  RESULTS
  Patients with mild AD had significantly lower functional connectivity (FC) within the default mode network and increased FC within the executive network. The mild AD group scored significantly lower in all domains of cognition compared with CHc. But fractional anisotropy did not significantly (p < 0.05) differ between the groups.
  
  
  CONCLUSIONS
  Resting state functional connectivity alterations are noted during initial stages of cognitive decline in AD, even when there are no significant white matter microstructural changes.
authors.affiliation: Department of Clinical Neuroscience, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India; Multimodal Brain Image Analysis Laboratory (MBIAL), National Institute of Mental Health and Neurosciences, Bangalore, India.
authors.forename: R
authors.initials: R
authors.lastname: Balachandar
authors.forename: J P
authors.initials: JP
authors.lastname: John
authors.forename: J
authors.initials: J
authors.lastname: Saini
authors.forename: K J
authors.initials: KJ
authors.lastname: Kumar
authors.forename: H
authors.initials: H
authors.lastname: Joshi
authors.forename: S
authors.initials: S
authors.lastname: Sadanand
authors.forename: S
authors.initials: S
authors.lastname: Aiyappan
authors.forename: P T
authors.initials: PT
authors.lastname: Sivakumar
authors.forename: S
authors.initials: S
authors.lastname: Loganathan
authors.forename: M
authors.initials: M
authors.lastname: Varghese
authors.forename: S
authors.initials: S
authors.lastname: Bharath
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000503:physiopathology*; D016880:Anisotropy; D001921:Brain / Q000473:pathology; D016022:Case-Control Studies; D003071:Cognition / Q000502:physiology; D060825:Cognitive Dysfunction / Q000503:physiopathology; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008568:Memory / Q000502:physiology; D008875:Middle Aged; D009434:Neural Pathways / Q000503:physiopathology
keywords: early diagnosis; functional biomarkers; mild Alzheimer's disease; resting state functional connectivity; white matter microstructural integrity