04_Visiual+Recognition+_+Agnosia

04_Visiual+Recognition+_+Agnosia - VisualRecognition...

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Visual Recognition
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Visual Processing n Millions of computations are performed on the  light patterns that fall on the retina before we  see images consciously. n Much of what goes on in the brain during  vision is unconscious (prior to awareness).   n Processing begins with  Sensory  Registration , as shown in the next slide.
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Visual system divides into three  pathways Thalamus Pulvinar nucleus Lateral geniculate nucleus Superior Colliculus Retina Ganglion cells bipolar cells photoreceptors Midbrain (eye movements) Optic tract divides into 3 paths: Cortex Parietal Primary visual
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Visual Pathways n As shown in the previous slide, after sensory  registration the visual pathway divides into: n The  eye-movement pathway  (superior colliculus) n How pathway  for all other movements (parietal  cortex) n Damage to how pathway causes visual apraxia. n What pathway  (occipital cortex) n Produces visual perception n Damage produces visual agnosia
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Visual Recognition n Sensory Registration n Feature Analysis n Patterns are constructed from features activated in  the primary visual cortex (occipital lobe) by visual  inputs. n Local form features such as shape and color are  invariant under orientation n Global, spatial, relational features are defined against a  fixed orientation n Integration
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04_Visiual+Recognition+_+Agnosia - VisualRecognition...

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