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Perceptual deficits of object identification: apperceptive agnosia
A David Milner1, Cristiana Cavina-Pratesi1
1Department of Psychology, Durham University, Durham, United Kingdom.
Handbook of Clinical Neurology
|March 10, 2018
Summary
Apperceptive object agnosia, or visual form agnosia, may be better understood as "imperception" caused by damage to the lateral occipital cortex (LO). This suggests spared dorsal stream functions may aid shape processing in affected individuals.
Area of Science:
- Neuroscience
- Cognitive Psychology
- Visual Perception
Background:
- Apperceptive object agnosia, now termed visual form agnosia, is traditionally classified as a deficit in object recognition.
- The dual-system model posits distinct ventral (perception) and dorsal (action) visual processing streams.
Observation:
- This study re-evaluates visual form agnosia, proposing it as "imperception" rather than true agnosia.
- Evidence suggests bilateral damage to the lateral occipital cortex (area LO) underlies this condition.
- Area LO is critical for visual form processing within the ventral stream.
Findings:
- Functional loss of area LO impairs visual form perception.
- The occipito-parietal dorsal stream, involved in visually-guided actions, may retain some shape processing capabilities.
- Patient D.F. provides key evidence for these observations.
Implications:
- Understanding visual form agnosia requires considering the role of the dorsal stream.
- Parietal lobe visual mechanisms interact with occipitotemporal systems in guiding actions.
- This perspective refines models of visual processing and neurological disorders.
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