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Human Eye. Structures of the Human Eye Anatomy of the Retina

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Anatomy of the Retina

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Human Eye Structures of the Human Eye Anatomy of the Retina Hyperpolarization of Photoreceptors Without light With light An Unobstructed View Structures of the Human Eye Densities of Retinal Receptors and Visual Acuity Lateral Inhibition in the Retina The Effect of Context on the Perception of Brightness Dot illusion Visual Pathways in the Human Brain The Lateral Geniculate Nucleus Blindsight Individuals with damage to their visual striate cortex V1 due to accidents or strokes reported partial or total blindness. In spite of this, when they were prompted they could "guess" with above-average accuracy about the presence and details of objects. Alternative pathways for visual information Retina Superior Colliculus Pulvinar Extrastriate A person with blindsight could detect slow or fast-moving stimuli, but was only aware of the fast ones. Visual motion information processing in the LGN A connection from LGN to the extrastriate visual areas V2, V3, V4 and visual motion area V5/MT Blindsight in Action: What Can the Different Sub-types of Blindsight Tell Us About the Control of Visually Guided Actions? James Danckert, Yves Rossetti Blindsight Connections of Cones to Bipolar Cells See Figure 10.8 Receptive Fields of Retinal Cells Receptive Fields of Cells at Various Levels in the Cat Visual System Circular Receptive Fields Can Be Combined to Produce Rod-Shaped Receptive Fields Spatial Frequencies Subsystem Ganglion NeuronsLGNVisual Cortex Color(L/M) Midget S(L+M) Bistratified Parvocellular in layers 3,4,5,6 Koniocellular Between each of the M and P layers V1 layer 4C beta - >V2 Thin -> V4 MotionDiffuse "Parasol"Magnocellular in layers 1, 2 V1 layer 4C -> 4B -> V2 Thick -> V5 Dynamic FormDiffuse "Parasol"Magnocellular in layers 1, 2 V1 layer 4B -> V2 Thick -> V3 Visual Subsystem Pathways Main Visual Areas in Monkey and Human Brains Functionally identified areas of human cortex using fMRI The retinotopic organization of the human middle temporal area MT/V5 and its cortical neighbors. Kolster et al. (2010) J. Neurosci. 30: Visual Areas interconnections FELLEMANN, D..J. & D.C. VAN ESSEN Distributed hierarchical processing in the primate cerebral cortex. Cerebral Cortex 1: 147. Why are there so many visual areas... ? COLOUR, FORM, STEREOSCOPIC DEPTH, MOTION All require very different processing strategies - most efficient if performed separately The Forest Has Eyes by Bev Dolittle