Spatial vision

Spatial VisionNick Nichiporuk

October 16, 2014

http://en.wikipedia.org/wiki/Snellen_chart

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

• 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

Visual Angle

http://en.wikipedia.org/wiki/Perceived_visual_angle

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).

http://www.doitbigtickets.com/venues/memorial-stadium-ca-berkeley.php

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/

http://foresighteyes.com/productdepth.html

Acuity for Low Contrast Stripes

• Spatial Frequency The number of grating cycles in a given unit of space. Measured in cycles per degree.

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).

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.

http://www.eyecalcs.com/DWAN/pages/v8/v8c017.html

http://www.brighamandwomens.org/Departments_and_Services/neurology/services/NeuroOphthamology/VisualFieldDeficits.aspx

David Hubel and Torsten Wiesel

http://www.ftpress.com/articles/article.aspx?p=1431818

Experimental Design

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

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

Elongated Rec. Fields & Orientation Tuning

http://ruccs.rutgers.edu/~ikovacs/SandP2000/prepI_3_1.html

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

http://www.sciencedirect.com/science/article/pii/S0896627301004974

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

http://www.wholistichealingresearch.com/93tausin.html

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

http://hubel.med.harvard.edu/book/82.jpg

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

Why Should we Care?

http://www.heightseyecare.com/images/amblyopia.jpg

Scoczenski & Nocia, 1999• Refer to Paper