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Analysis of pathways mediating preserved vision after striate cortex lesions
Mircea Ariel Schoenfeld1, Toemme Noesselt, Dorothe Poggel
1Department of Neurology II, University of Magdeburg, 39120 Magdeburg, Germany. ariel@neuro2.med.uni-magdeburg.de
Annals of Neurology
|November 26, 2002
Summary
Patients with Riddoch syndrome and V1 damage can still perceive visual stimuli. This study reveals preserved visual processing via extrastriate pathways bypassing the primary visual cortex (V1).
Area of Science:
- Neuroscience
- Visual Neuroscience
- Clinical Neurology
Background:
- Homonymous hemianopsia and Riddoch syndrome can result from posterior cerebral artery strokes.
- Primary visual cortex (V1) lesions typically cause severe visual field deficits.
Observation:
- A patient with a V1 lesion demonstrated preserved, albeit limited, visual abilities in the hemianopic field.
- This included reporting movement, color change, and movement direction discrimination above chance levels.
Findings:
- Functional neuroimaging revealed activation in extrastriate visual areas (V4/V8, V5, V2/V3) in response to stimuli in the hemianopic field.
- Activity occurred earlier in higher-tier areas (V4/V8, V5) than lower-tier areas (V2/V3).
- Increased functional connectivity was observed between V4/V8 and V5 in the lesioned hemisphere.
Implications:
- Visual perception in Riddoch syndrome may rely on subcortical pathways bypassing V1.
- These pathways may initially project to higher-tier visual areas (V5, V4/V8) before reaching lower-tier areas (V2/V3).
- This challenges traditional models of visual processing following V1 damage.