title: Altered cortical visual processing in PD with hallucinations: an fMRI study.
abstract: OBJECTIVE
  To compare fMRI activation during two visual stimulation paradigms in Parkinson disease (PD) subjects with chronic visual hallucinations vs PD patients who had never hallucinated.
  
  
  METHODS
  Twelve pairs of PD subjects, matched for age, PD duration, and dopaminergic drug exposure duration, participated in this study. The authors examined group differences in activation during stroboscopic (flashing) vs no visual stimulation and kinematic (apparent motion) vs stationary visual stimulation.
  
  
  RESULTS
  During stroboscopic stimulation, non-hallucinating PD subjects showed significantly greater activation in the parietal lobe and cingulate gyrus compared to hallucinating PD subjects. In contrast, the hallucinating subjects showed significantly greater activation in the inferior frontal gyrus and the caudate nucleus. During kinematic stimulation, non-hallucinating PD subjects showed significantly greater activation in area V5/MT, parietal lobe, and cingulate gyrus compared to hallucinating PD subjects. Hallucinating PD subjects showed significantly greater activation in the superior frontal gyrus.
  
  
  CONCLUSIONS
  PD patients with chronic visual hallucinations respond to visual stimuli with greater frontal and subcortical activation and less visual cortical activation than non-hallucinating PD subjects. Shifting visual circuitry from posterior to anterior regions associated primarily with attention processes suggests altered network organization may play a role in the pathophysiology of visual hallucinations in PD.
authors.affiliation: Department of Neurological Sciences, Rush University Medical Center, 1725 West Harrison Street, Suite 309, Chicago, IL 60612, USA. gstebbin@rush.edu
authors.forename: G T
authors.initials: GT
authors.lastname: Stebbins
authors.forename: C G
authors.initials: CG
authors.lastname: Goetz
authors.forename: M C
authors.initials: MC
authors.lastname: Carrillo
authors.forename: K J
authors.initials: KJ
authors.lastname: Bangen
authors.forename: D A
authors.initials: DA
authors.lastname: Turner
authors.forename: G H
authors.initials: GH
authors.lastname: Glover
authors.forename: J D E
authors.initials: JD
authors.lastname: Gabrieli
mesh_terms: D000368:Aged; D001288:Attention / Q000502:physiology; D016022:Case-Control Studies; D002421:Caudate Nucleus / Q000473:pathology / Q000503:physiopathology; D002540:Cerebral Cortex / Q000473:pathology / Q000503:physiopathology*; D002908:Chronic Disease; D015331:Cohort Studies; D015259:Dopamine Agents / Q000627:therapeutic use; D005625:Frontal Lobe / Q000473:pathology / Q000503:physiopathology; D006179:Gyrus Cinguli / Q000473:pathology / Q000503:physiopathology; D006212:Hallucinations / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D010296:Parietal Lobe / Q000473:pathology / Q000503:physiopathology; D010300:Parkinson Disease / Q000150:complications*; D010775:Photic Stimulation; D014795:Visual Pathways / Q000473:pathology / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology*
chemical_list: D015259:Dopamine Agents