Vision: From Eye to Brain (Chap 3) - Princeton...
Transcript of Vision: From Eye to Brain (Chap 3) - Princeton...
![Page 1: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/1.jpg)
Vision: From Eye to Brain (Chap 3)
Lecture 7
Jonathan PillowSensation & Perception (PSY 345 / NEU 325)
Princeton University, Fall 2017
![Page 2: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/2.jpg)
early visual pathway
optic nerve
optic chiasm
optic tract
lateral geniculate nucleus (LGN)
optic radiations
primary visual cortex (“V1”)
thalamus:
cortex:
(aka “striate cortex”)right visual
worldleft visual
world
eye eye
![Page 3: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/3.jpg)
• Acuity: measure of finest visual detail that can be resolved
![Page 4: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/4.jpg)
Measuring Visual Acuity
Snellen E test• Herman Snellen invented this method for designating visual acuity
in 1862
• Notice that the strokes on the E form a small grating pattern
![Page 5: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/5.jpg)
Visual Acuity
• Acuity: The smallest spatial detail that can be resolved
• in the lab
![Page 6: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/6.jpg)
Acuityeye doctor: 20 / 20 (your distance / avg person’s distance) for letter identification
vision scientist: visual angle of one cycle of the finest grating you can see
![Page 7: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/7.jpg)
• striped pattern is a “sine wave grating”
• visual system “samples” the grating at cone locations
explaining acuity stimulus on retina
percept
acuity limit: 1’ of arccone spacing in fovea: 0.5’ of arc
![Page 8: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/8.jpg)
more “channels”: spatial frequency channels
spatial frequency: the number of cycles of a grating per unit of visual angle (usually specified in degrees)
• think of it as: # of bars per unit length
low frequency intermediate high frequency
![Page 9: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/9.jpg)
Why sine gratings?• Provide useful decomposition of images
Technical term: Fourier decomposition
(But the real reason: some neuroscientists read a math book and decided it would be cool to apply some fancy math to vision science!)
![Page 10: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/10.jpg)
• mathematical decomposition of an image (or sound) into sine waves.
Fourier decomposition
“image”1 sine wave
reconstruction:
2 sine waves
3 sine waves
4 sine waves
![Page 11: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/11.jpg)
“Fourier Decomposition” theory of V1
• Summation of two spatial sine waves• any pattern can be broken down
into a sum of sine waves
claim: role of V1 is to do “Fourier decomposition”, i.e., break images down into a sum of sine waves
![Page 12: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/12.jpg)
• mathematical decomposition of an image (or sound) into sine waves.
Fourier decomposition
Original image High Frequencies Low Frequencies
![Page 13: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/13.jpg)
original
low medium high
![Page 14: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/14.jpg)
Retinal Ganglion Cells: tuned to spatial frequency
Response of a ganglion cell to sine gratings of different frequencies
![Page 15: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/15.jpg)
The contrast sensitivity function
Human contrast sensitivity illustration of this sensitivity
![Page 16: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/16.jpg)
Image Illustrating Spatial Frequency Channels
![Page 17: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/17.jpg)
Image Illustrating Spatial Frequency Channels
![Page 18: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/18.jpg)
If it is hard to tell who this famous person is, try squinting or defocusing
“Lincoln illusion” Harmon & Jules 1973
![Page 19: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/19.jpg)
“Gala Contemplating the Mediterranean Sea, which at 30 meters becomes the portrait of Abraham Lincoln (Homage to Rothko)”
- Salvador Dali (1976)
![Page 20: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/20.jpg)
- Salvador Dali (1976)
“Gala Contemplating the Mediterranean Sea, which at 30 meters becomes the portrait of Abraham Lincoln (Homage to Rothko)”
![Page 21: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/21.jpg)
Ipsilateral: Referring to the same side of the body
Contralateral: Referring to the opposite side of the body
lateral geniculate nucleus (LGN): one on each side of the brain • this is where axons of retinal ganglion cells synapse
Organization:• represents contralateral
visual field• segregated into eye-
specific layers• segregated into M and P
layers
![Page 22: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/22.jpg)
Primary Visual Cortex
• Striate cortex: known as primary visual cortex, or V1
• “Primary visual cortex” = first place in cortex where visual information is processed(Previous two stages: retina and LGN are pre-cortical)
![Page 23: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/23.jpg)
Receptive Fields: monocular vs. binocular
- LGN cells: responds to one eye or the other, never both
- V1 cells: can respond to input from both eyes
(but V1 neurons still tend to have a preferred eye - they spike more to input from one eye)
V1
LGN
![Page 24: Vision: From Eye to Brain (Chap 3) - Princeton Universitypillowlab.princeton.edu/teaching/sp2017/slides/Lec07_Eye...Vision: From Eye to Brain (Chap 3) Lecture 7 Jonathan Pillow Sensation](https://reader034.fdocuments.in/reader034/viewer/2022051603/5fefa79b9bf9ef703b65229d/html5/thumbnails/24.jpg)
Topography: mapping of objects in space onto the visual cortex
• cortical magnification - unequal representation of fovea vs. periphery in cortex - a misnomer, because “magnification” already present in retina
• contralateral representation - each visual field (L/R) represented in opposite hemisphere
(that is, the amount of space in cortex for each part of the visual field is given by the number of fibers coming in from LGN)