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Functional connectivity and the failure to retrieve meaning from shape in visual object agnosia.
Journal article

Functional connectivity and the failure to retrieve meaning from shape in visual object agnosia.

  • Ptak R Division of Neurorehabilitation, Department of Clinical Neurosciences, Geneva University Hospitals, Geneva, Switzerland; Laboratory of Cognitive Neurorehabilitation, Department of Clinical Neurosciences, Medical School, University of Geneva, Geneva, Switzerland; Faculty of Psychology and Educational Sciences, University of Geneva, Geneva, Switzerland. Electronic address: radek.ptak@hcuge.ch.
  • Lazeyras F Department of Radiology and Medical Informatics, University of Geneva, Geneva, Switzerland.
  • 2018-12-29
Published in:
  • Brain and cognition. - 2019
Functional connectivity
Lateral occipital cortex
Object recognition
Visual object agnosia
fMRI
Aged
Agnosia
Brain Mapping
Humans
Magnetic Resonance Imaging
Male
Occipital Lobe
Pattern Recognition, Visual
Visual Pathways
Visual Perception
English The neural mechanisms underlying the access to object knowledge from early representations of shape are little known. Functional imaging studies support the view that representations of visual properties are distributed across occipito-temporal cortex of both cerebral hemispheres. By contrast, brain lesion studies show that focal occipito-temporal damage may lead to object agnosia - a specific impairment of object recognition. How does distributed processing fit with functional specialization implied by the existence of stimulus-specific agnosias? Using fMRI we studied functional connectivity (FC) in a patient with object agnosia following left lateral occipital damage. Despite intact global and local processing of 2D and 3D object structure, the patient made consistent object identification errors. Seven experiments testing naming, visual matching or object priming showed that his errors mainly reflected the global shape similarity between objects. Compared to controls the patient exhibited strongly reduced FC between the damaged left and the intact right medial/lateral occipital cortex. In addition, controls showed stronger connectivity between the right occipital cortex and the left and right inferior and anterior temporal cortices. Interestingly, the patient also showed compensatory increases of FC between dorsal occipital and medial parietal cortex. These findings show that focal damage to the lateral occipital cortex may have global effects on representations of objects in bilateral occipito-temporal cortex, thus supporting the view that bilaterally distributed coding is necessary for the retrieval of associative knowledge from shape.
Language
  • English
Open access status
closed
Identifiers
Persistent URL
https://sonar.ch/global/documents/232875
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