Lecture 8. Sensation and Perception (Part II for class)

Lecture 8. Sensation and Perception (Part II for class) -...

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Introduction to Psychology PSYC 1001, Section E Monday, Oct. 20, 2008 (Part II)
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Today’s class (Objectives) The Visual System Dorsal vs. Ventral Stream (Perception vs. Action) Colour Vision Stimulus for Colour; Complementary Theories Perceiving Forms, Patterns and Objects Feature Analysis; Gestalt Principles; Perceptual Hypotheses Depth Perception Perceptual Constancies & Optical Illusions
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Visual Pathways to the Brain How does visual information get to the brain? Light Signal
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Basic Visual Pathway Optic chiasm: The point at which the optic nerves from the nasal (inside) retina of each eye cross over (and then project to the opposite half of the brain) Note that… Axons from the outside half of each eye project to the same (ipsilateral) side of the brain THUS, Information from the L visual field goes to the R side of the brain ; information from the R visual field goes to the L side of the brain
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Central Visual Pathways Main (Geniculostriate) Pathway: Projections from the retina (via the optic nerves) Lateral geniculate nucleus 1° visual cortex Second (Tectopulvinar) Pathway: Projections from the retina Superior colliculus (Tectum) Thalamus (Pulvinar nucleus) Visual cortex
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Tectopulvinar (2 nd ) Pathway Principal Function: Coordination of visual input (superior colliculus) with other sensory input (e.g., Auditory information) Provides information regarding location (“where”) Mediates pupillary light reflex (pretectum)
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Main (Geniculostriate) Pathway Two Subdivisions… Parallel processing ! Simultaneous extraction of different kinds of information from the same input Parvocellular Channel Magnocellular Channel Parvo = small Magno = large Perception of color Perception of brightness (and movement) 1° input from cones (i.e., via ganglion cells) 1° input from rods
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Visual Processing: Dorsal and Ventral Streams Dorsal Stream: Visual control of action The “how/where” pathway ( how action is to be guided toward objects; where objects are located) Pathway that originates in the occipital cortex and projects to the posterior parietal cortex , which also receives input from the tectopulvinar (2 nd ) pathway Ventral Stream: Perception (recognition) of the external world The “what” pathway (identifies what an object is) Pathway that originates in the occipital cortex and projects to the (Occipito-) temporal cortex
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Visual Processing: The Cortex Thus, most visual input eventually arrives in the 1° visual cortex (located in the occipital lobe)
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Visual Processing: The Cortex Receptive Field: Region of the visual world that stimulates a receptor cell (e.g., photoreceptor) or neuron (e.g., ganglion cell, LGN cell, cortical cell)
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Visual Processing: The Cortex How do cortical cells respond to light?
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Lecture 8. Sensation and Perception (Part II for class) -...

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