title: Visual perceptual organization deficits in Alzheimer's dementia.
abstract: BACKGROUND
  Deficits in visual processing are a prominent feature of Alzheimer's disease (AD), yet the cognitive and neuropathological mechanisms underlying these deficits are poorly understood. In the current study, we examined the hypothesis that perceptual organization is specifically impaired in AD compared to other dementias.
  
  
  METHODS
  We examined perceptual organization with a psychophysically well-controlled measure of contour integration in patients with AD (n = 17), vascular dementia (n = 5), frontotemporal dementia (n = 5) and mild cognitive impairment (n = 10) and 11 age-matched healthy controls.
  
  
  RESULTS
  Patients with AD differed significantly in their ability to detect contours comprised of Gabor elements as detection relied increasingly on long-range spatial interactions. Impairments in contour integration were particularly pronounced in AD patients with atrophy and gliosis of white matter in the occipital lobe. Deficits in perceptual organization were not found in patients with other dementias and participants with mild cognitive impairment.
  
  
  CONCLUSIONS
  These results suggest that a subgroup of AD patients is characterized by a specific deficit in visual perceptual organization, which might reflect the impaired functional integrity of occipital cortico-cortical pathways.
authors.affiliation: Department of Neurophysiology, Max-Planck Institute for Brain Research, Department of Psychiatry, Frankfurt am Main, Germany. uhlhaas@mpih-frankfurt.mpg.de
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Uhlhaas
authors.forename: Johannes
authors.initials: J
authors.lastname: Pantel
authors.forename: Heinrich
authors.initials: H
authors.lastname: Lanfermann
authors.forename: David
authors.initials: D
authors.lastname: Prvulovic
authors.forename: Corinna
authors.initials: C
authors.lastname: Haenschel
authors.forename: Konrad
authors.initials: K
authors.lastname: Maurer
authors.forename: David E J
authors.initials: DE
authors.lastname: Linden
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D005556:Form Perception; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009413:Nerve Fibers, Myelinated / Q000473:pathology; D009483:Neuropsychological Tests; D009778:Occipital Lobe / Q000473:pathology / Q000503:physiopathology*; D010775:Photic Stimulation; D014795:Visual Pathways / Q000473:pathology / Q000503:physiopathology*