title: The default mode network is disrupted in Parkinson's disease with visual hallucinations.
abstract: BACKGROUND
  Visual hallucinations (VH) are one of the most striking nonmotor symptoms in Parkinson's disease (PD), and predict dementia and mortality. Aberrant default mode network (DMN) is associated with other psychoses. Here, we tested the hypothesis that DMN dysfunction contributes to VH in PD.
  
  
  METHODS
  Resting state functional data was acquired from individuals with PD with VH (PDVH) and without VH (PDnonVH), matched for levodopa drug equivalent dose, and a healthy control group (HC). Independent component analysis was used to investigate group differences in functional connectivity within the DMN. In addition, we investigated whether the functional changes associated with hallucinations were accompanied by differences in cortical thickness.
  
  
  RESULTS
  There were no group differences in cortical thickness but functional coactivation within components of the DMN was significantly lower in both PDVH and PDnonVH groups compared to HC. Functional coactivation within the DMN was found to be greater in PDVH group relative to PDnonVH group.
  
  
  CONCLUSIONS
  Our study demonstrates, for the first time that, within a functionally abnormal DMN in PD, relatively higher "connectivity" is associated with VH. We postulate that aberrant connectivity in a large scale network affects sensory information processing and perception, and contributes to "positive" symptom generation in PD.
authors.affiliation: Department of Psychiatry, Queen Mary Hospital, The University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Nailin
authors.initials: N
authors.lastname: Yao
authors.forename: Richard
authors.initials: R
authors.lastname: Shek-Kwan Chang
authors.forename: Charlton
authors.initials: C
authors.lastname: Cheung
authors.forename: Shirley
authors.initials: S
authors.lastname: Pang
authors.forename: Kui Kai
authors.initials: KK
authors.lastname: Lau
authors.forename: John
authors.initials: J
authors.lastname: Suckling
authors.forename: James B
authors.initials: JB
authors.lastname: Rowe
authors.forename: Kevin
authors.initials: K
authors.lastname: Yu
authors.forename: Henry
authors.initials: H
authors.lastname: Ka-Fung Mak
authors.forename: Siew-Eng
authors.initials: SE
authors.lastname: Chua
authors.forename: Shu Leong
authors.initials: SL
authors.lastname: Ho
authors.forename: Grainne M
authors.initials: GM
authors.lastname: McAlonan
mesh_terms: D000368:Aged; D001921:Brain / Q000098:blood supply / Q000473:pathology*; D005260:Female; D006212:Hallucinations / Q000150:complications* / Q000473:pathology*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010300:Parkinson Disease / Q000150:complications* / Q000473:pathology*; D012044:Regression Analysis
chemical_list: D010100:Oxygen
keywords: MRI; coactivation; cortical thickness; function; resting