The Midget and Parasol Channels

Transcription

1 The visual and oculomotor systems Peter H. Schiller, year 2006 The Midget and Parasol Channels

2 MIDGET SYSTEM PARASOL SYSTEM or Neuronal response profile ON OFF ON OFF time

3 Midget system cones ON OFF ON OFF bipolars IPL, OFF IPL, ON ON OFF ON OFF Green ON and OFF Red ON and OFF ganglion cells ganglion cells

4 Blue/yellow system OFF ON OFF ON OFF? YELLOW BLUE BLUE YELLOW Yellow/blue ganglion cell Blue/yellow ganglion cell

5 Midget and blue/yellow system cones? ON OFF ON OFF ON OFF ON OFF ON OFF bipolars H A IPL, OFF IPL, ON ON OFF YELLOW BLUE BLUE YELLOW ON OFF Green ON and OFF Yellow/blue Blue/yellow Red ON and OFF ganglion cells ganglion cell ganglion cell ganglion cells

6 Parasol system cones H ON OFF bipolars A IPL, OFF IPL, ON ON OFF ganglion cells

7 Number of midget and parasol cells per unit area as a function of eccentricity fovea 6 mber of cells Nu midget parasol 5 4 periphery layers 4 layers midget/parasol ratio: fovea: 8 to 1 periphery: 1 to 1 fovea periphery eccentricity

8 Projections of the retinal ganglion cells

9 The central connections of the midget and parasol channels

10 Tissue block with injections inject blocker record V 1 V 4 MT Parvo Magno LGN?

11 Vl complex cell response to moving light bar Normal Parvo Injection Spikes per bin Magno Injection Paired Injection Recovery Figure by MIT OCW.

12 V 1 Midget Mixed V 2 Parasol w LGN P M? MT V 4 Midget Parasol PARIETAL LOBE TEMPORAL LOBE FRONTAL LOBE

13 Lesion studies

14 Behavioral procedures

15 Detection

16 Detection

17 Discrimination

18 Performance Monitor

19 The lesions

20 PERCEPTUAL FUNCTIONS TESTED Contrast Sensitivity Color Pattern Texture Shape Stereopsis Flicker Motion Brightness Scotopic Vision

21 Contrast sensitivity

22 Contrast Sensitivity Contrast 0.4 Normal MLGN Lesion 0.5 PLGN Lesion Spatial Frequency (cy/deg) Figure by MIT OCW.

23 Color vision

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25 Color Discrimination Seneca Percent Correct Normal PLGN MLGN Figure by MIT OCW.

26 Brightness perception

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28 The perception of brightness in photopic vision nt C o rrect Normal Normal rce Pe Parvo lesion Magno lesion Percent Luminance Contrast

29 Pattern and texture perception

30 Texture and Pattern Discrimination Percent Correct N P M Texture N P M Pattern Figure by MIT OCW.

31 Stereoscopic depth perception

32 Stereoscopic depth perception Parvo lesion 100 Magno lesion Percent Correct Normal Parvo Lesion Magno Lesion Normal Disparity in minutes

33 Motion perception

34 Motion detection

35 Motion detection

36 Motion detection

37 Motion detection 100 Parvo lesion 100 Magno lesion Normal Percent Correct Normal Parvo Lesion Magno Lesion Percent Contrast

38 The perception of flicker

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41 Flicker perception 100 Parvo lesion 100 Magno lesion Percent Correct Normal Parvo lesion Normal Magno lesion Flicker Rate (cy/sec)

42 Deficit magnitude following PLGN, MLGN, V4 and MT lesions NC VISUAL FU VISUAL CAPACITY PLGN MLGN V 4 MT color vision severe none mild none texture perception severe none mild none pattern perception fine severe none mild none TIONSshape coarse mild none none none perceptionfine severe none mild none brightness perception none none none none coarse scotopic vision none none none none contrast sensitivity fine severe none mild mild BASIC coarse mild none none mild stereopsis fine severe none none none coarse pronounced none none none motion perception none moderate none moderate flicker perception none severe none pronounced IN TE RMED IATE choice of "lesser" stimuli severe none severe none visual learning not tested not tested severe none object transformation not tested not tested pronounced not tested

43 Functions of the midget and parasol systems: The midget system : color texture fine form fine stereo The parasol system: fast flicker fast, low contrast motion Both Systems: brightness coarse form coarse stereo slow flicker slow, high contrast motion scotopic vision

44 Spatial Frequency H Processing Capacity L L Midget System Parasol System H Temporal Frequency H L L H Figure by MIT OCW.

45 Summary: 1. Two major channels originating in the retina are the midget and the parasol. 2. In central retina the receptive field center of midget RGC and parvocellular LGN cells is compised of a single cone. 3. Parasol cells have much larger receptive fields; the cone input is mixed in both the center and the surround. 4. The midget and parasol cell ratio from center to periphery changes from 8 to 1 to 1 to The midget and parasol systems converge on some of the cells in V1. 6. V4 receives input from both the midget and parasol cells. 7. The major input to MT is from the parasol cells. 8. The midget system extends the range of vision in the wavelength and high spatial frequency domains 9. The parasol system extends the range of vision in the high temporal frequency domain.

46 Recording in V4 Magno Block Parvo Block Before Block After Block Time (msec) Time (msec) Figure by MIT OCW.

47 Recording in MT Magno Block Parvo Block Before Block After Block Time (msec) Time (msec) Figure by MIT OCW.

48 Average blocking index V4 MT Parvocellular Block Magnocellular Block Figure by MIT OCW.

49 V 1 Midget Mixed V 2 Parasol w LGN P M Midget Parasol

50 How selective are individual horizontal cells in their connections with cones? Model 1 Model 2

51 V 1 V 2 w LGN P M MT V 4 Midget Parasol PARIETAL LOBE TEMPORAL LOBE FRONTAL LOBE

52 stripes: thin inter thick V 2 V Ca 4Cb parasol midget 500

53 The blue/yellow koniocellular system cones ON OFF? ON OFF OFF ON bipolars outer IPL inner IPL yellow blue ganglion cells