title: Resting activity in visual and corticostriatal pathways in Parkinson's disease with hallucinations.
abstract: BACKGROUND
  Visual hallucinations are an important non-motor complication of Parkinson's disease (PD) and carry a negative prognosis. Their biological basis is uncertain, but may relate to the activity of resting state networks in brain. We therefore aimed to investigate functional activity of brain in patients with visual hallucinations (PDVH) in resting state compared to patients without hallucinations (PDnonVH) and a healthy control group (HC).
  
  
  METHODS
  Resting state functional MRI was acquired and the primary analysis compared the amplitude of low-frequency fluctuations (ALFF) across groups. This informed a secondary analysis, in the PD groups only, comparing functional connectivity between a 'seed' region in the occipital lobe and the rest of the brain.
  
  
  RESULTS
  Individuals with PDVH showed lower ALFF in bilateral lingual gyrus and cuneus and greater ALFF in temporo-parietal regions, medial temporal gyrus and cerebellum than PDnonVH and HC. PDnonVH also had lower ALFF in occipitoparietal region and greater ALFF in medial temporal gyrus, temporo-parietal and cerebellum regions than HC. Functional connectivity analysis revealed that, although both PD groups had lower occipital functional connectivity relative to the HC group, occipital - corticostriatal connectivity was significantly higher in those with PDVH compared with PDnonVH.
  
  
  CONCLUSIONS
  Our study reveals widespread hemodynamic alterations in PD. However, within a functionally abnormal occipital lobe, those with PDVH have even lower ALFF than non-hallucinators, but have higher occipital functional connectivity with cortical-striatal regions. These findings suggest disruption of pathways underpinning both primary visual perceptual and intrinsic visual integration may contribute to visual hallucinations 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.affiliation: Division of Neurology, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong.
authors.forename: Shirley
authors.initials: S
authors.lastname: Pang
authors.affiliation: Department of Psychiatry, Queen Mary Hospital, The University of Hong Kong, Pokfulam, Hong Kong; State Key Laboratory for Cognitive Sciences, The University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Charlton
authors.initials: C
authors.lastname: Cheung
authors.affiliation: Division of Neurology, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong.
authors.forename: Richard Shek-Kwan
authors.initials: RS
authors.lastname: Chang
authors.affiliation: Division of Neurology, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong.
authors.forename: Kui Kai
authors.initials: KK
authors.lastname: Lau
authors.affiliation: Department of Psychiatry and Behavioural and Clinical Neuroscience Institute, University of Cambridge, United Kingdom & Cambridge and Peterborough Foundation NHS Trust, UK.
authors.forename: John
authors.initials: J
authors.lastname: Suckling
authors.affiliation: Department of Psychiatry, Queen Mary Hospital, The University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Kevin
authors.initials: K
authors.lastname: Yu
authors.affiliation: Department of Diagnostic Radiology, The University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Henry Ka-Fung
authors.initials: HK
authors.lastname: Mak
authors.affiliation: Department of Psychiatry, Queen Mary Hospital, The University of Hong Kong, Pokfulam, Hong Kong; State Key Laboratory for Cognitive Sciences, The University of Hong Kong, Pokfulam, Hong Kong; Department of Forensic and Neurodevelopmental Science, Institute of Psychiatry, King's College London, London SE5 8AZ, UK. Electronic address: grainne.mcalonan@kcl.ac.uk.
authors.forename: Grainne
authors.initials: G
authors.lastname: McAlonan
authors.affiliation: Division of Neurology, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong. Electronic address: slho@hku.hk.
authors.forename: Shu-Leong
authors.initials: SL
authors.lastname: Ho
authors.affiliation: Department of Psychiatry, Queen Mary Hospital, The University of Hong Kong, Pokfulam, Hong Kong; State Key Laboratory for Cognitive Sciences, The University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Siew-Eng
authors.initials: SE
authors.lastname: Chua
mesh_terms: D000368:Aged; D002540:Cerebral Cortex / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism*; D005260:Female; D006212:Hallucinations / Q000175:diagnosis / Q000378:metabolism*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000378:metabolism; D010300:Parkinson Disease / Q000175:diagnosis / Q000378:metabolism*; D012146:Rest / Q000502:physiology; D014793:Visual Cortex / Q000378:metabolism*; D014795:Visual Pathways / Q000378:metabolism*
keywords: ALFF; Functional connectivity; Parkinson's disease; Resting state; Visual hallucinations