1. The responses of on-center and off-center retinal ganglion cells

Transcription

1 1. The responses of on-center and off-center retinal ganglion cells

2 2. Responses of an on-center ganglion cell to different light conditions

3 3. Responses of an on-center ganglion cells to different light condition

4 4. Generation of the receptive field surround of an on-center retinal ganglion cell Origin of center-surround receptive fields of RGC: When the surround is dark: Surround cones are depolarized. Surround cones release glutamate onto horizontal cells. Horizontal cells depolarize. Horizontal cells release GABA onto center cone. (GABAergic) Center cone hyperpolarizes more: similar to if it got more light!

5 5. Targets of retinal ganglion cells Suprachiasmatic nucleus of hypothalamus: circadian rhythm primary visual cortex, V-1, area 17, striate ctx

6 6. Midsagittal view of the human brain

7 7. Brainstem cranial nerve nuclei

8 8. Targets of retinal ganglion cells: Pupillary light reflex Optic nerve (CN II): afferent; sensory Oculomotor nerve (CN III): efferent; motor

9 9. Targets of retinal ganglion cells: Pupillary light reflex The consensual pupillary reflex is caused by bilateral projections: 1. Each eye projects to both pretecta 2. Each pretectum projects to both Edinger-Westphal nuclei. 3. Each Edinger-Westphal nucleus projects to the ipsilateral pupil.

10 10. Pupillary Reflex Problems Problem: Light in left eye does not cause pupillary reflex in either eye. Light in right eye causes pupillary reflex in both eyes. Cause: Left optic nerve (CN II) or left retina damage.

11 11. Pupillary Reflex Problems Problem: Light in either eye causes pupillary reflex in right eye only. Cause: Left oculomotor nerve (CN III), or left Edinger-Westphal nucleus damage.

12 12. The Retinal Image is Left/Right and Up/Down Inverted

13 13. Monocular and Binocular Visual Fields

14 14. Decussation of nasal retinal axons in optic chiasm Optic nerve (CN II): axons from one eye. Optic tract: axons from both eyes. Left optic nerve Contralaterality: caused by decussation of the nasal retinal axons at the optic chiasm

15 15. Retino-geniculo-cortical pathway primary visual cortex, V-1, area 17, striate ctx

16 16. Types of Visual Field Deficits Right monocular blindness Bitemporal hemianopsia Left homonymous hemianopsia Left superior quadrantanopsia Left homonymous hemianopsia with foveal sparing

17 17. Visuotopic (Retinotopic) Organization of Primary Visual Cortex

18 18. Visuotopic (Retinotopic) Organization of Primary Visual Cortex Retinotopic map in primary visual cortex

19 19. Layers in LGN, and Ocular Dominance Columns in V-1 Lateral geniculate nucleus (LGN) Primary visual cortex (V1)

20 20. Transneuronal Labeling with Radioactive Amino Acids

21 21. Transneuronal Labeling with Radioactive Amino Acids

22 22. Effect of monocular deprivation on ocular dominance columns in the macaque monkey Normal Monocular Deprivation

23 23. Effect of monocular deprivation on terminal arborizations of LGN axons in V1

24 24. Developmental Critical Period for Ocular-Dominance Plasticity

25 25. Effect of short period of monocular deprivation at height of critical period in cat

26 26. Ocular dominance plasticity caused by strabismus induced during critical period

27 27. Orientation-Selective V1 Receptive Fields

28 28. Hubel & Wiesel Ice Cube model

29 29. The Population Vector for Inferring Orientation Each vector represents one neuron in V1 The direction of the vector is the neuron s preferred orientation The magnitude of the vector is the neuron s firing rate 35 Question: How might the brain infer the orientation of the stimulus?

30 30. The Population Vector for Inferring Orientation The Population Vector: a method the brain may use to infer stimulus orientation Vector additon: the geometric (tip-to-tail) approach: population vector

31 31. The Population Vector for Inferring Orientation Finding the Population Vector with Trigonometry (review of vector addition): 1) Find the vertical and horizontal components of each vector: o 88sin(45 ) = 62.2 o 88cos(45 ) = ) Add: sin(-45 o ) = cos(-45 o) = 24.7 Resultant vector vertical component = = 37.5 Resultant vector horizontal component = = ) Find resultant vector s angle: Arctan(37.5 / 86.9) = 23 o 23 o

32 32. Binocular disparity and stereopsis

33 33. Binocular disparity and stereopsis Two objects at the same depth from the observer: red object image at identical location on the two retinae (no disparity) fixation point fovea fovea

34 34. Binocular disparity and stereopsis Two objects at different depths from the observer: red object image at different location on the two retinae (disparity) fixation point fovea fovea

35 35. Depth illusion: the two red objects hit the retina just as a single closer object would. fixation point fixation point

36 36. How to Create a Stereogram!

37 37. Cortical Visual Areas

38 38. Cortical Visual Areas Lesion to MT: cerebral akinetopsia Lesion to V4: cerebral achromatopsia

39 39. Area MT Neuronal Receptive Fields Felleman, DJ & Kaas, JH (1984) Receptive-field properties of neurons in middle temporal visual area (MT) of owl monkeys. J. Neurophysiol 52:

40 40. The MT Population Vector for Inferring Direction of Motion The MT Population Vector: a method the brain may use to infer stimulus direction Vector additon: the geometric (tip-to-tail) approach: population vector