title: 3D Shape Perception in Posterior Cortical Atrophy: A Visual Neuroscience Perspective.
abstract: Posterior cortical atrophy (PCA) is a rare focal neurodegenerative syndrome characterized by progressive visuoperceptual and visuospatial deficits, most often due to atypical Alzheimer's disease (AD). We applied insights from basic visual neuroscience to analyze 3D shape perception in humans affected by PCA. Thirteen PCA patients and 30 matched healthy controls participated, together with two patient control groups with diffuse Lewy body dementia (DLBD) and an amnestic-dominant phenotype of AD, respectively. The hierarchical study design consisted of 3D shape processing for 4 cues (shading, motion, texture, and binocular disparity) with corresponding 2D and elementary feature extraction control conditions. PCA and DLBD exhibited severe 3D shape-processing deficits and AD to a lesser degree. In PCA, deficient 3D shape-from-shading was associated with volume loss in the right posterior inferior temporal cortex. This region coincided with a region of functional activation during 3D shape-from-shading in healthy controls. In PCA patients who performed the same fMRI paradigm, response amplitude during 3D shape-from-shading was reduced in this region. Gray matter volume in this region also correlated with 3D shape-from-shading in AD. 3D shape-from-disparity in PCA was associated with volume loss slightly more anteriorly in posterior inferior temporal cortex as well as in ventral premotor cortex. The findings in right posterior inferior temporal cortex and right premotor cortex are consistent with neurophysiologically based models of the functional anatomy of 3D shape processing. However, in DLBD, 3D shape deficits rely on mechanisms distinct from inferior temporal structural integrity.
  
  
  CONCLUSIONS
  Posterior cortical atrophy (PCA) is a neurodegenerative syndrome characterized by progressive visuoperceptual dysfunction and most often an atypical presentation of Alzheimer's disease (AD) affecting the ventral and dorsal visual streams rather than the medial temporal system. We applied insights from fundamental visual neuroscience to analyze 3D shape perception in PCA. 3D shape-processing deficits were affected beyond what could be accounted for by lower-order processing deficits. For shading and disparity, this was related to volume loss in regions previously implicated in 3D shape processing in the intact human and nonhuman primate brain. Typical amnestic-dominant AD patients also exhibited 3D shape deficits. Advanced visual neuroscience provides insight into the pathogenesis of PCA that also bears relevance for vision in typical AD.
authors.affiliation: Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium, Department of Experimental Psychology, University of Oxford, Oxford OX1 3UD, United Kingdom.
authors.forename: Céline R
authors.identifier: http://orcid.org/0000-0001-6686-7262
authors.initials: CR
authors.lastname: Gillebert
authors.affiliation: Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium.
authors.forename: Jolien
authors.initials: J
authors.lastname: Schaeverbeke
authors.affiliation: Cyclotron Research Centre, University of Liège, 4000 Liège, Belgium.
authors.forename: Christine
authors.initials: C
authors.lastname: Bastin
authors.affiliation: Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium.
authors.forename: Veerle
authors.initials: V
authors.lastname: Neyens
authors.affiliation: Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium, Neurology Department.
authors.forename: Rose
authors.identifier: http://orcid.org/0000-0002-2631-9234
authors.initials: R
authors.lastname: Bruffaerts
authors.affiliation: Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium.
authors.forename: An-Sofie
authors.initials: AS
authors.lastname: De Weer
authors.affiliation: Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium, Neurology Department.
authors.forename: Alexandra
authors.identifier: http://orcid.org/0000-0002-8690-1226
authors.initials: A
authors.lastname: Seghers
authors.affiliation: Radiology Department, and.
authors.forename: Stefan
authors.initials: S
authors.lastname: Sunaert
authors.affiliation: Division of Nuclear Medicine, University Hospitals Leuven, 3000 Leuven, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Van Laere
authors.affiliation: Department of Neurology, University Hospital Brussels, 1090 Brussels, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Versijpt
authors.affiliation: Psychiatry Department, University Hospitals Leuven, 3000 Leuven, Belgium.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Vandenbulcke
authors.affiliation: Cyclotron Research Centre, University of Liège, 4000 Liège, Belgium.
authors.forename: Eric
authors.identifier: http://orcid.org/0000-0003-2520-9241
authors.initials: E
authors.lastname: Salmon
authors.affiliation: Department of Psychology, The Ohio State University, Columbus, Ohio 43210.
authors.forename: James T
authors.initials: JT
authors.lastname: Todd
authors.affiliation: Laboratory of Neuro- and Psychophysiology, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium, Department of Neuroscience, University of Parma, 43125 Parma, Italy, and.
authors.forename: Guy A
authors.identifier: http://orcid.org/0000-0002-8179-9584
authors.initials: GA
authors.lastname: Orban
authors.affiliation: Laboratory for Cognitive Neurology, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium, Neurology Department, Alzheimer Research Centre KU Leuven, Leuven Research Institute for Neuroscience and Disease, KU Leuven, 3000 Leuven, Belgium rik.vandenberghe@uz.kuleuven.ac.be.
authors.forename: Rik
authors.identifier: http://orcid.org/0000-0001-6237-2502
authors.initials: R
authors.lastname: Vandenberghe
mesh_terms: D000368:Aged; D000377:Agnosia / Q000503:physiopathology; D000544:Alzheimer Disease / Q000473:pathology / Q000503:physiopathology; D001284:Atrophy; D001766:Blindness / Q000209:etiology / Q000503:physiopathology; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000473:pathology* / Q000503:physiopathology; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D020961:Lewy Body Disease / Q000473:pathology / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology; D009044:Motor Cortex / Q000473:pathology / Q000503:physiopathology; D019636:Neurodegenerative Diseases / Q000473:pathology / Q000503:physiopathology*; D009483:Neuropsychological Tests; D009929:Organ Size; D049268:Positron-Emission Tomography; D013702:Temporal Lobe / Q000473:pathology / Q000503:physiopathology
keywords: Alzheimer's disease; Lewy body; depth perception; fMRI; voxel-based morphometry