spatial vision
TRANSCRIPT
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Spatial VisionNick Nichiporuk
October 16, 2014
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http://en.wikipedia.org/wiki/Snellen_chart
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Spatial VisionVision Acuity The smallest spatial detail that can be resolved.
Sine Wave Grating A grating with a sinusoidal luminance profile.
Cycle For a grating, a pair consisting of one dark bar and one bright bar.
Visual Angle The angle subtended by an object at the retina
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• Visual Acuity: The smallest spatial detail that can be resolved• Cycle: For a grating, a pair consisting of one dark bar and one bright
bar. http://www.cns.nyu.edu/~david/courses/perception/lecturenotes/channels/channels.html
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Visual Angle
http://en.wikipedia.org/wiki/Perceived_visual_angle
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Visual Angle
Under ideal conditions, humans with very good visual acuity can resolve gratings when one cycle subtends an angle of approximately 1 minute of arc (0.017 degrees).
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http://www.doitbigtickets.com/venues/memorial-stadium-ca-berkeley.php
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Fundamental Limit of Spatial Vision• Limit of 0.017 degrees is determined by the spacing of photoreceptors in the
retina.
http://read.uconn.edu/PSYC3501/Lecture04/
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http://foresighteyes.com/productdepth.html
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Acuity for Low Contrast Stripes
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• Spatial Frequency The number of grating cycles in a given unit of space. Measured in cycles per degree.
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How is Visual Acuity affected if Contrast of Stripes is Reduced?
• Otto Schade showed people sine wave gratings with different spatial frequencies and had the adjust the contrast of the gratings until they could just be detected (1956).
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How is Visual Acuity affected if Contrast of Stripes is Reduced?
• Otto Schade showed people sine wave gratings with different spatial frequencies and had the adjust the contrast of the gratings until they could just be detected (1956).
Intuitively, one might think that the wider the stripes – the lower the spatial frequency – the easier it is to distinguish light stripes from dark stripes.
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http://www.eyecalcs.com/DWAN/pages/v8/v8c017.html
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http://www.brighamandwomens.org/Departments_and_Services/neurology/services/NeuroOphthamology/VisualFieldDeficits.aspx
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David Hubel and Torsten Wiesel
http://www.ftpress.com/articles/article.aspx?p=1431818
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Experimental Design
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First Exploration of Primary Visual Cortex (V1)• Receptive fields are elongated, as opposed to circular, so they respond
to bars, lines, and edges.• Orientation tuning Tendency of neurons in V1 to respond optimally to
certain orientation and less to others• Complex Cells Neuron whose receptive field characteristics cannot be
easily predicted by mapping with spots of light• Ocular Dominance Neurons in V1 respond to information from both
eyes, but prefer one eye over another• End Stopped Neuron’s firing rate sensitive to length of stimulus
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First Exploration of Primary Visual Cortex (V1)• Receptive fields are elongated, as opposed to circular, so they respond
to bars, lines, and edges.• Orientation tuning Tendency of neurons in V1 to respond optimally to
certain orientation and less to others• Complex Cells Neuron whose receptive field characteristics cannot be
easily predicted by mapping with spots of light• Ocular Dominance Neurons in V1 respond to information from both
eyes, but prefer one eye over another• End Stopped Neuron’s firing rate sensitive to length of stimulus
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Elongated Rec. Fields & Orientation Tuning
http://ruccs.rutgers.edu/~ikovacs/SandP2000/prepI_3_1.html
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First Exploration of Primary Visual Cortex (V1)• Receptive fields are elongated, as opposed to circular, so they respond
to bars, lines, and edges.• Orientation tuning Tendency of neurons in V1 to respond optimally to
certain orientation and less to others• Complex Cells Neuron whose receptive field characteristics cannot be
easily predicted by mapping with spots of light• Ocular Dominance Neurons in V1 respond to information from both
eyes, but prefer one eye over another• End Stopped Neuron’s firing rate sensitive to length of stimulus
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http://www.sciencedirect.com/science/article/pii/S0896627301004974
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First Exploration of Primary Visual Cortex (V1)• Receptive fields are elongated, as opposed to circular, so they respond
to bars, lines, and edges.• Orientation tuning Tendency of neurons in V1 to respond optimally to
certain orientation and less to others• Complex Cells Neuron whose receptive field characteristics cannot be
easily predicted by mapping with spots of light• Ocular Dominance Neurons in V1 respond to information from both
eyes, but prefer one eye over another• End Stopped Neuron’s firing rate sensitive to length of stimulus
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http://www.wholistichealingresearch.com/93tausin.html
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First Exploration of Primary Visual Cortex (V1)• Receptive fields are elongated, as opposed to circular, so they respond
to bars, lines, and edges.• Orientation tuning Tendency of neurons in V1 to respond optimally to
certain orientation and less to others• Complex Cells Neuron whose receptive field characteristics cannot be
easily predicted by mapping with spots of light• Ocular Dominance Neurons in V1 respond to information from both
eyes, but prefer one eye over another• End Stopped Neuron’s firing rate sensitive to length of stimulus
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http://hubel.med.harvard.edu/book/82.jpg
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Summary• Receptive fields are elongated, as opposed to circular, so they respond
to bars, lines, and edges.• Orientation tuning Tendency of neurons in V1 to respond optimally to
certain orientation and less to others• Complex Cells Neuron whose receptive field characteristics cannot be
easily predicted by mapping with spots of light• Ocular Dominance Neurons in V1 respond to information from both
eyes, but prefer one eye over another• End Stopped Neuron’s firing rate sensitive to length of stimulus
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Why Should we Care?
http://www.heightseyecare.com/images/amblyopia.jpg
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Scoczenski & Nocia, 1999• Refer to Paper