Lecture slides for PSY-2 Ch07: Vision

1. Ch07: Vision
➔Visual Transduction
➔Visual Processing in the CNS
➔Receptive Fields for Vision
➔Color Vision

2. CASE STUDY: PATIENT D.F.
Seeing without perceiving.

3. CASE STUDY: PATIENT D.F.
Seeing without perceiving.

4. VISUAL TRANSDUCTION
4

5. Figure 7.1 Structures of the Human
• CORNEA
• PUPIL
• IRIS
• LENS
• CILIARY MUSCLE
• RETINA
• OPTIC NERVE
VISUAL TRANSDUCTION

6. VISUAL TRANSDUCTION

7. VISUAL TRANSDUCTION

8. Figure 7.2 Focusing Images on the
Retina
• ACCOMMODATION: using
ciliary muscles to change lens
shape
• MYOPIA: nearsightedness
• HYPEROPIA: farsightedness
• PRESBYOPIA: age-related
farsightedness
VISUAL TRANSDUCTION

9. Figure 7.3 Anatomy of the Retina
(Part 1)
Cells in the Retina
– PHOTORECEPTORS:
sensory neurons that
detect light
– BIPOLAR CELLS: connect
photoreceptors and
ganglion cells
– GANGLION CELLS: axons
form the optic nerve
VISUAL TRANSDUCTION

10. Figure 7.3 Anatomy of the Retina
(Part 1)
Cells in the Retina
– HORIZONTAL CELLS: link
receptor cells and
bipolar cells
– AMACRINE CELLS: link
bipolar cells and ganglion
cells
VISUAL TRANSDUCTION

11. Figure 7.3 Anatomy of the Retina
(Part 1)
• Only ganglion cells
generate action
potentials
• CONVERGENCE: info
from many
photoreceptors
converges onto each
ganglion cell
VISUAL TRANSDUCTION

12. 12
SCOTOPIC SYSTEM (RODS):
•100 million per eye
•Low light
•Rhodopsin
•Insensitive to color
•Low visual acuity
•Peripheral
VISUAL TRANSDUCTION

13. 13
PHOTOPIC SYSTEM (CONES):
•4 million per eye
•Bright light
•Opsin (3 Types)
•Detect color
•High visual acuity
•Central
VISUAL TRANSDUCTION

14. VISUAL TRANSDUCTION

15. Figure 7.4 Hyperpolarization of
Photoreceptors
VISUAL TRANSDUCTION

16. • OPTIC DISC: where blood
vessels and ganglion cell axons
leave the eye
• BLIND SPOT: due to lack of
photoreceptors in the optic
disc
• FOVEA: center of retina; high
density of smaller, tightly-
packed cones
VISUAL TRANSDUCTION

17. VISUAL TRANSDUCTION

18. VISUAL TRANSDUCTION

19. VISUAL TRANSDUCTION

20. VISUAL TRANSDUCTION

21. Ch07: Vision
➔Visual Transduction
➔Visual Processing in the CNS
➔Receptive Fields for Vision
➔Color Vision

22. Visual Processing in the Brain
• LATERAL GENICULATE NUCLEUS
(LGN): the visual part of the
thalamus
• OPTIC RADIATIONS: axons of LGN
neurons that terminate in the
occipital cortex
CNS VISUAL PROCESSING

23. Visual Processing in the Brain
• PRIMARY VISUAL CORTEX (V1): region
of occipital cortex where most visual
information first arrives
• EXTRASTRIATE CORTEX: visual cortex
outside of V1
CNS VISUAL PROCESSING

24. CNS VISUAL PROCESSING
Optic Nerve
Optic Chiasm
Lateral Geniculate Nucleus
Superior Colliculus
Striate Cortex (V1)
Optic Radiations
Retina

26. CNS VISUAL PROCESSING

27. TOPOGRAPHIC
PROJECTION:
organization that
preserves the point-
to-point map between
neighboring parts of
space
CNS VISUAL PROCESSING

28. • SCOTOMA: perceptual gap,
due to injury
• BLINDSIGHT: inability to
consciously perceive visual
cues, yet able to make visual
discrimination
CNS VISUAL PROCESSING

29. • Where does information go after it leaves V1?
CNS VISUAL PROCESSING

30. Animation 7.3
Click here to watch an animation of the visual
pathways in the brain.

31. Video 7.1
Click here to watch a video about object
recognition.

32. Ch07: Vision
➔Visual Transduction
➔Visual Processing in the CNS
➔Receptive Fields for Vision
➔Color Vision

33. RECEPTIVE FIELDS FOR VISION
At rest, in darkness,
photoreceptors release
GLU

34. RECEPTIVE FIELDS FOR VISION
GLU depolarizes some bipolar
cells and hyperpolarizes others
• ON-CENTER BIPOLAR CELLS:
turning on light excites the
cell
• OFF-CENTER BIPOLAR CELLS:
turning off light in the center
of the field excites the cells

35. Bipolar cells also release
GLU, which always
depolarizes ganglion cells
RECEPTIVE FIELDS FOR VISION

36. Types of Ganglion Cells
• On-center bipolar cells excite
ON-CENTER GANGLION CELLS,
when light is turned on
• Off-center bipolar cells excite
OFF-CENTER GANGLION CELLS,
when light is turned off
RECEPTIVE FIELDS FOR VISION

37. RECEPTIVE FIELD: the stimulus region and features that
affect the activity of a cell in a sensory system
–On-center/off-surround
–Off-center/on-surround
RECEPTIVE FIELDS FOR VISION

38. Figure 7.13 Receptive Fields of
Retinal Cells (Part 1)
RECEPTIVE FIELDS FOR VISION

39. Animation 7.4
Click here to watch a video overview of
receptive fields for vision.

40. LATERAL INHIBITION: sensory receptor cells inhibit
information from neighboring receptor cells
RECEPTIVE FIELDS FOR VISION

41. RECEPTIVE FIELDS FOR VISION

42. Neurons in the visual cortex have varied receptor
fields:
• SIMPLE CORTICAL CELLS: also called bar or edge
detectors—respond to an edge or bar of a particular
width, orientation, and location
• COMPLEX CORTICAL CELLS: also respond to a bar of a
particular width and orientation, but may be located
anywhere in the visual field
RECEPTIVE FIELDS FOR VISION

43. RECEPTIVE FIELDS FOR VISION

44. RECEPTIVE FIELDS FOR VISION

45. RECEPTIVE FIELDS FOR VISION

46. RECEPTIVE FIELDS FOR VISION

47. RECEPTIVE FIELDS FOR VISION

48. RECEPTIVE FIELDS FOR VISION

49. Ch07: Vision
➔Visual Transduction
➔Visual Processing in the CNS
➔Receptive Fields for Vision
➔Color Vision

50. COLOR VISION

51. COLOR VISION
Dimensions of color perception:
1. Brightness–varies from dark to light
2. Hue–varies throughout all colors
3. Saturation–varies from full colors to
gray at the center

52. COLOR VISION
Cones contain one of
three pigments, called
opsins, with overlapping
but different peaks of
sensitivity.

53. In the second stage of color processing:
– Most ganglion cells and LGN cells fire in response to some
wavelengths and are inhibited by others
– COLOR OPPONENT CELL: has opposite firing responses to
different regions of the spectrum
– EX: a plus L/minus M (+L/–M) cell is stimulated above
600 nm and inhibited at shorter wavelengths
COLOR VISION

54. COLOR VISION

55. COLOR VISION