Psych_115_-_Vision_CONT

Psych_115_-_Vision_CONT - PRINCIPLES OF BEHAVIORAL...

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PRINCIPLES OF BEHAVIORAL NEUROSCIENCE Vision (continued) May 10, 2011
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Optic Chiasm The optic nerves from each eye join at the optic chiasm Some axons stay on the same side (ipsilateral), some cross (contralateral) The goal is that all axons carrying information about the left visual field end up on the right and so forth…
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Axons Crossing (or NOT!) at the Optic Chiasm The nasal (medial retina) views the non- overlapping part of the visual field, so fibers from ganglion cells in this part cross over. The temporal (lateral) retina views a shared part of the visual field, so those fibers often stay ipsilateral.
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Lateral Geniculate Nucleus The LGN has six main layers: Parvocellular – four dorsal layers of the LGN – small cells, small receptive fields Magnocellular – two ventral layers – large cells, large receptive fields Different layers receive input from different eyes (2 each for P and 1 each for M) Cells in LGN still have center-surround configurations (like ganglion cells)
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LGN Striate Cortex (Occipital Lobe) Axons of postsynaptic cells in the LGN form optic radiations and project to the occipital cortex . Striate cortex another name for primary visual cortex (V1) Extrastriate cortex visual cortical areas outside the striate
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V1 Visual Cortex Neurons Simple cortical neurons Each simple cell monitors a small part of the contralateral visual field It responds to bars and edges present in that location Orientation matters To do this, it must already have “access” to the information of
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V1 Receptive Fields V1 has representations for four parts of a visual stimulus: Location in the visual field Orientation Ocular dominance Color An ocular dominance column is a region of cortex with greater synaptic input from one eye. Vertical columns are arranged in ocular dominance slabs neurons in all layers respond better to one eye.
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Two Forms of Topographic Organization
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Two Forms of Topographic Organization
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Retinotopic Map in V1 In addition to sorting neurons according to whether they are fired by: R Particular eyes R Particular orientations V1 is retinotopically organized, meaning that cells that are near to one another are likely to receive information from ganglion cells that are nearby to one another on the retina
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Ventral “What” Pathway V1 V2 V2 begins putting together information from multiple neurons in V1, building more complex representations of objects that depend upon multiple features and some “approximations”
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This note was uploaded on 06/13/2011 for the course PSYCH 115 taught by Professor Shaine during the Spring '07 term at UCLA.

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Psych_115_-_Vision_CONT - PRINCIPLES OF BEHAVIORAL...

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