title: Resting-State Functional Connectivity Changes Associated with Visuospatial Cognitive Deficits in Patients with Mild Alzheimer Disease.
abstract: Alzheimer disease (AD) is a neurodegenerative disorder characterized by progressive disconnection of various brain networks leading to neuropsychological impairment. Pathology in the visual association areas has been documented in presymptomatic AD and therefore we aimed at examining the relationship between brain connectivity and visuospatial (VS) cognitive deficits in early AD.
  
  
  
  Tests for VS working memory, episodic memory and construction were used to classify patients with AD (n = 48) as having severe VS deficits (n = 12, female = 4) or mild deficits (n = 11, female = 4). Resting-state functional magnetic resonance imaging and structural images were acquired as per the standard protocols. Between-group differences in resting-state functional connectivity (rsFC) were examined by dual regression analysis correcting for age, gender, and total brain volume.
  
  
  
  Patients with AD having severe VS deficits exhibited significantly reduced rsFC in bilateral lingual gyri of the visual network compared to patients with mild VS deficits.
  
  
  
  Reduced rsFC in the visual network in patients with more severe VS deficits may be a functional neuroimaging biomarker reflecting hypoconnectivity of the brain with progressive VS deficits during early AD.
authors.affiliation: Department of Clinical Neuroscience, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, India.
authors.forename: Rakesh
authors.initials: R
authors.lastname: Balachandar
authors.forename: Srikala
authors.initials: S
authors.lastname: Bharath
authors.forename: John P
authors.initials: JP
authors.lastname: John
authors.forename: Himanshu
authors.initials: H
authors.lastname: Joshi
authors.forename: Shilpa
authors.initials: S
authors.lastname: Sadanand
authors.forename: Jitender
authors.initials: J
authors.lastname: Saini
authors.forename: Keshav J
authors.initials: KJ
authors.lastname: Kumar
authors.forename: Mathew
authors.initials: M
authors.lastname: Varghese
mesh_terms: D000368:Aged; D000377:Agnosia / Q000175:diagnosis / Q000209:etiology; D000544:Alzheimer Disease / Q000175:diagnosis / Q000523:psychology; D001921:Brain / Q000000981:diagnostic imaging / Q000473:pathology; D003071:Cognition / Q000502:physiology; D063132:Connectome / Q000379:methods; D005260:Female; D059907:Functional Neuroimaging / Q000379:methods*; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D012720:Severity of Illness Index
keywords: Mild Alzheimer disease; Resting-state functional connectivity; Visuospatial cognitive deficits