1. Week 14: Neurobiology of Vision Part 2

2. Agenda for today Neurobiology of Vision: Part 2
Begin Learning & Memory
Thursday: Continue Learning and Memory
Course evaluations are available:

3. From the Eyes:
Lateral geniculate nucleus: Receives most of the visual input. This is the information we perceive
Hypothalamus (Suprachiasmatic Nucleus): Takes light information to keep circadian rhythm set
Pretectum: Brainstem nucleus controls pupillary dilation
Superior colliculus: Deals with head movements and eye movements (saccades)

5. Encoding in the retina
We will define receptive fields at the level of the ganglion cells forward.
What type of stimulus does a ganglion cell respond to?

6. Encoding: Ganglion cells have center/surround receptive fields
We will define receptive fields at the level of the ganglion cells forward.
What type of stimulus does a ganglion cell respond to?

7. Rods send information to magnocellular pathway
Cones send information to
parvocellular pathway
Magnocellular pathway: The majority of axons in the optic nerve (70-80%)
Specialized for - dim light
- no color information
- poor resolution (many rods to one ganglion)
- motion detection
Parvocellular pathway: About 10-20%
- bright light
- high resolution (very few cones to each ganglion)
- color
- texture
- depth
Other cell types, less than 10%

9. From the Eyes:
Lateral geniculate nucleus: Receives most of the visual input. This is the information we perceive
Hypothalamus (Suprachiasmatic Nucleus): Takes light information to keep circadian rhythm set
Pretectum: Brainstem nucleus controls pupillary dilation
Superior colliculus: Deals with head movements and eye movements (saccades)

10. Lateral Geniculate Nucleus
Note the RETINOTOPIC organization
M = Magnocellular P = Parvocellular
C = contralateral I = ipsilateral
©1997 by National Academy of Sciences
Meissirel C et al. PNAS 1997;94:

12. Primary Visual Cortex
Hubel Wiesel
LGN neurons
Simple Cell (V1)

13. Creating simple cells

14. A single patch of V1 encodes all of the information coming in from a single receptive field of the retina (borders, color, locationmovement).

15. Hypercolumns in Primary Visual Cortex (V1)
Simple cells code orientation.
Cells in blobs code color.
Occular dominance columns begin to give depth information.

16. Cortical vision processing: Two “streams”

17. Two different sources of motion illusion
Superior colliculus
Visual cortex

18. From the Eyes:
Lateral geniculate nucleus: Receives most of the visual input. This is the information we perceive
Hypothalamus (Suprachiasmatic Nucleus): Takes light information to keep circadian rhythm set
Pretectum: Brainstem nucleus controls pupillary dilation
Superior colliculus: Deals with head movements and eye movements (saccades)

19. What does the superior colliculus do?
Here do the mirror – eye movement demonstration. SC suppresses visual inputs during saccades (rapid eye movements)

20. +
Superior Colliculus also controls microsaccades to prevent saturation of rods and cones. Try staring at this cross – its pretty easy

21. BLUE +
Now stare at the cross for a while – it begins to get difficult

22. Afterimage occurs because cones become saturated and ganglion cells adapt. Superior colliculus tries to prevent this by microsaccades that desaturate cones.

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Now stare at the cross for a while – it begins to get difficult

24. Afterimage occurs because cones become saturated and ganglion cells adapt. Superior colliculus tries to prevent this by microsaccades that desaturate cones.

27. Fatiguing neurons in MT (V5)

28. Split-depth illusions
Reveal the role of competition between networks of motion-sensitive neurons

29. Top-down processing
Our experience and expectations change what we perceive

32. Bistable perceptions
Our experience and expectations change what we perceive
And reveal competing networks of neurons