1 / 34

Spatial Vision 2

Spatial Vision 2. PSY 295 – Sensation & Perception Christopher DiMattina , PhD. Visual acuity. Visual acuity. Smallest spatial detail that can be resolved Simple acuity test – humans with good vision can resolve 1 minute of visual angle (1/60 th degree). Visual angle.

miron
Download Presentation

Spatial Vision 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Spatial Vision 2 PSY 295 – Sensation & Perception Christopher DiMattina, PhD

  2. Visual acuity PSY 295 - Grinnell College - Fall 2012

  3. Visual acuity • Smallest spatial detail that can be resolved • Simple acuity test – humans with good vision can resolve 1 minute of visual angle (1/60th degree) PSY 295 - Grinnell College - Fall 2012

  4. Visual angle • Visual angle is how we measure the size of images on retina • Affected by size and distance of object PSY 295 - Grinnell College - Fall 2012

  5. Photoreceptor spacing • Limit to visual acuity given by photoreceptor spacing PSY 295 - Grinnell College - Fall 2012

  6. Retinal eccentricity and cortical magnification PSY 295 - Grinnell College - Fall 2012

  7. Visual crowding • A consequence of poor acuity in the periphery is visual crowding, where objects that can be seen in isolation become indistinguishable in clutter PSY 295 - Grinnell College - Fall 2012

  8. Visual crowding PSY 295 - Grinnell College - Fall 2012

  9. Web activity: Foveal acuity • http://sites.sinauer.com/wolfe3e/chap3/foveaF.htm PSY 295 - Grinnell College - Fall 2012

  10. Sine wave gratings Gratings of different spatial frequency PSY 295 - Grinnell College - Fall 2012

  11. Contrast • Contrast threshold is % difference in luminance between light and dark bars needed to detect a grating • Contrast sensitivity is measured as reciprocal of threshold • Intuitively, one might expect highest sensitivity for low spatial frequencies (wide stripes) PSY 295 - Grinnell College - Fall 2012

  12. Contrast sensitivity function PSY 295 - Grinnell College - Fall 2012

  13. Contrast sensitivity function view in book from a distance of 2 meters PSY 295 - Grinnell College - Fall 2012

  14. Pop Quiz • What limits our ability to perceive high spatial frequencies? PSY 295 - Grinnell College - Fall 2012

  15. Spatial frequency channels PSY 295 - Grinnell College - Fall 2012

  16. Multi-resolution analysis • Visual receptive fields recorded in animal V1 have a variety of orientations and spatial frequencies PSY 295 - Grinnell College - Fall 2012

  17. Selective adaptation • Since we can’t record from human neurons, how can we know that human visual cortex also has neurons tuned to orientation? • Selective adaptation PSY 295 - Grinnell College - Fall 2012

  18. A hypothetical neural population PSY 295 - Grinnell College - Fall 2012

  19. After adaptation to 20 degree bar PSY 295 - Grinnell College - Fall 2012

  20. Adaptation demonstration PSY 295 - Grinnell College - Fall 2012

  21. Spatial frequency adaptation PSY 295 - Grinnell College - Fall 2012

  22. Spatial frequency PSY 295 - Grinnell College - Fall 2012

  23. Spatial frequency channels • If separate channels are used to analyze information, threshold for detecting a compound stimulus should be explained by thresholds for individual components PSY 295 - Grinnell College - Fall 2012

  24. Different kinds of information PSY 295 - Grinnell College - Fall 2012

  25. Fun Demo PSY 295 - Grinnell College - Fall 2012

  26. Development of spatial vision PSY 295 - Grinnell College - Fall 2012

  27. How does spatial vision develop? • Measure from babies • Preferential looking • Visually evoked potentials PSY 295 - Grinnell College - Fall 2012

  28. Preferential looking PSY 295 - Grinnell College - Fall 2012

  29. Visually evoked potentials PSY 295 - Grinnell College - Fall 2012

  30. VEP PSY 295 - Grinnell College - Fall 2012

  31. Infants less sensitive to high spatial frequencies PSY 295 - Grinnell College - Fall 2012

  32. Visual development • Critical period after birth for eyes to wire up with cortex • Interference with vision during this time can prevent normal wiring and vision • Amblyopia or lazy eye is when one eye has reduced visual acuity because of abnormal experience (i.e. cataracts) PSY 295 - Grinnell College - Fall 2012

  33. Amblyopia • Cataracts must be removed early to permit normal visual development • Other causes of amblyopia are strabismus (incorrect eye alignment) or anisometropia (different refractive errors). PSY 295 - Grinnell College - Fall 2012

  34. Web activities • http://sites.sinauer.com/wolfe3e/chap3/striaterfF.htm PSY 295 - Grinnell College - Fall 2012

More Related