visual_cog_08 - 1 Visual Cognition September 11, 2008 2...

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1 1 Visual Cognition September 11, 2008 2 Overview of Visual Cognition • Visual system: mission critical • Multivariate inputs, unitary experience • Multiple types of vision means many types of units in a distributed visual network • Segregating vs. parsing • Visual experience reveals nature of underlying representations • Theory >> data 3 Who’s Coming to Dinner? • Gestalt Psychology (interested in basic dimensions of perceptual organization) • Cognitive Psychology (interested primarily in effects of cognitive operations on visual experience) • Cognitive Neuropsychology (interested in effects of selective lesions of visual cortex on visual behavior) • Electrophysiology (interested in single- and multiple-unit activity of cells in visual cortex) • Cognitive science (interested in developing overall theories of visual experience and object recognition) 4 Sensation and Perception Sensation : Conscious outcome of sense organs and projection regions. (“I detect something”, not necessarily conscious, and not necessarily meaningful) Perception : means by which information acquired from the environment via the sense organs is transformed (organized) into conscious experiences of objects, events, sounds, tastes, etc. (“I know, recognize, appreciate what I am sensing, and it means something to me”) 5 Three Stages of Visual Processing • Reception: absorption of physical energy by receptors • Transduction: translation of physical energy into electrochemical activity of the nervous system • Coding: how information is encoded and represented; relationship between aspects of the physical stimulus and resultant nervous system activity (e.g., rate, temporal patterning of neuronal activity) – Population coding – Sparse coding 6 Basic Perceptual Phenomena You Already Know About Size and Shape Constancies : reflect mechanisms whereby perception of a distal object stays the same despite proximal changes in the perception – implies storage of a “structural representation” Depth Cues: monocular or binocular sources of information that convey information about relative distance of objects from viewer – involve cues about the structure, movement, and proximity of objects 7 8 9 Milner & Goodale: Perception-Action Model • Alternative to the Mishkin-Ungerleider model – Dorsal: “How do I interact with that object”? – Ventral: “What is that object”?
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2 • Evidence: distinctions between object recognition and visual control of action; Balint’s syndrome; optic ataxia 10 Perceptual Organization • Two complementary issues: Organizing coherent objects and events out of segregated sensory/perceptual inputs (“binding”) “Parsing” the perceptual world; understanding which inputs belong together and which come from separate objects – 11 Perceptual Organization • Gestalt Psychology Law of Prägnanz : perceptual system organizes to the simplest and most stable shape possible from the
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This note was uploaded on 12/01/2011 for the course CLP 7934 taught by Professor Staff during the Fall '08 term at University of Florida.

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visual_cog_08 - 1 Visual Cognition September 11, 2008 2...

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