- Exam 3 Thursday, 4/11
- Warm-up
- From eye to brain
- Prep for Thursday's exam
2019-04-10 10:51:18
Today's topics
Warm-up
What property of electromagmentic radiation does our perception of color depend upon?
- Intensity
- Wavelength
- Direction
- Refraction
What property of electromagmentic radiation does our perception of color depend upon?
- Intensity
- Wavelength
- Direction
- Refraction
Why does Gilmore say the retina is physiologically backwards?
- Light triggers action potentials from axon to dendrite
- Light hyperpolarizes photoreceptors
- Light depolarizes photoreceptors
- Night vision is the reverse of day vision
Why does Gilmore say the retina is physiologically backwards?
- Light triggers action potentials from axon to dendrite
- Light hyperpolarizes photoreceptors
- Light depolarizes photoreceptors
- Night vision is the reverse of day vision
Which type of photoreceptor is more numerous in the retina?
- Rods
- Cones
- Bipolar cells
- Retinal ganglion cells
Which type of photoreceptor is more numerous in the retina?
- Rods
- Cones
- Bipolar cells
- Retinal ganglion cells
From eye to brain
Center-surround receptive fields
Center-surround receptive fields
- Center region
- Excites (or inhibits)
- Surround region
- Does the opposite
- Bipolar cells & Retinal Ganglion cells ->
- Most activated by "donuts" of light/dark
- Local contrast (light/dark differences)
What's a reddish-green look like?
What's a reddish-green look like?
Opponent processing
Opponent processing
- Black vs. white (achromatic)
- Long (red) vs. Medium (green) wavelength cones
- (Long + Medium) vs. Short cones
- Can't really see reddish-green or bluish-yellow
From eye to brain
From eye to brain
- Retinal ganglion cells
- 2nd/II cranial (optic) nerve
- Optic chiasm
- Lateral Geniculate Nucleus (LGN) of thalamus (90% of projections)
From eye to brain
- Hypothalamus
- Suprachiasmatic nucleus (SCN)
- Superior colliculus & brainstem
LGN
LGN
- 6 layers + intralaminar zone
- Parvocellular (small cells): chromatic
- Magnocellular (big cells): achromatic
- Koniocellular (chromatic - short wavelength?)
- Retinotopic map of opposite visual field
From LGN to V1
From LGN to V1
- Via optic radiations
- Primary visual cortex (V1) in occipital lobe
Human V1
Measuring retinotopy in V1
Retinotopy in V1
- Fovea overrepresented
- Analogous to somatosensation
- High acuity in fovea vs. lower outside it
- Upper visual field/lower (ventral) V1 and vice versa
V1 has laminar, columnar organization
V1 has laminar, columnar organization
- 6 laminae (layers)
- Input: Layer 4
- Output: Layers 2-3 (to cortex), 5 (to brainstem), 6 (to LGN)
V1 has laminar, columnar organization
- Columns
- Orientation/angle
- Spatial frequency
Orientation/angle tuning
From center-surround receptive fields to line detection
Spatial frequency tuning
Low == gist || high == details 
V1 has laminar, columnar organization
- Columns
- Color/wavelength
- Eye of origin, ocular dominance
Ocular dominance columns
Ocular dominance signals retinal disparity
Beyond V1
Beyond V1
- Larger, more complex receptive fields
- Dorsal stream (where/how)
- Toward parietal lobe
- Ventral stream (what)
What is vision for?
- What is it? (form perception)
- Where is it? (space perception)
- How do I get from here to there (action control)
- What time (or time of year) is it?
References
Dougherty, R. F., V. M. Koch, A. A. Brewer, B. Fischer, J. Modersitzki, and B. A. Wandell. 2003. “Visual Field Representations and Locations of Visual Areas V1/2/3 in Human Visual Cortex.” Journal of Vision 3 (10): 1–1. doi:10.1167/3.10.1.
Panichello, Matthew F., Olivia S. Cheung, and Moshe Bar. 2013. “Predictive Feedback and Conscious Visual Experience.” Perception Science 3: 620. doi:10.3389/fpsyg.2012.00620.