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Functional connectivity and the failure to retrieve meaning from shape in visual object agnosia
Radek Ptak1, François Lazeyras2
1Division 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.
Brain and Cognition
|December 29, 2018
Summary
Damage to the left occipital cortex impairs object recognition by disrupting functional connectivity (FC) across the brain. This highlights the importance of bilateral occipito-temporal networks for accessing object knowledge from shape.
Area of Science:
- Neuroscience
- Cognitive Neuroscience
- Neuroimaging
Background:
- Object recognition relies on accessing knowledge from visual shape representations.
- Functional imaging suggests visual processing is distributed across the occipito-temporal cortex.
- Brain lesions can cause object agnosia, challenging the understanding of distributed processing and functional specialization.
Purpose of the Study:
- To investigate functional connectivity (FC) in a patient with object agnosia due to left lateral occipital damage.
- To understand how focal brain damage affects the distributed neural networks involved in object recognition.
- To reconcile findings from functional imaging and lesion studies regarding object knowledge retrieval.
Main Methods:
- Used functional magnetic resonance imaging (fMRI) to study functional connectivity (FC).
- Assessed a patient with object agnosia resulting from left lateral occipital cortex damage.
- Conducted seven experiments on naming, visual matching, and object priming, alongside control comparisons.
Main Results:
- The patient exhibited object identification errors, primarily based on global shape similarity, despite intact 2D/3D structure processing.
- Reduced FC was observed between the damaged left and intact right medial/lateral occipital cortex in the patient compared to controls.
- Controls showed stronger connectivity between the right occipital cortex and bilateral inferior/anterior temporal cortices; the patient displayed compensatory FC increases in dorsal occipital-medial parietal regions.
Conclusions:
- Focal damage to the lateral occipital cortex can globally impact object representations in the bilateral occipito-temporal cortex.
- Bilaterally distributed neural coding is essential for retrieving associative knowledge from visual shape.
- Understanding functional connectivity is crucial for explaining deficits in object recognition after focal brain lesions.
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