The visual and oculomotor systems Peter H. Schiller, year 2006 The Midget and Parasol Channels
MIDGET SYSTEM PARASOL SYSTEM or Neuronal response profile ON OFF ON OFF time
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
Blue/yellow system OFF ON OFF ON OFF? YELLOW BLUE BLUE YELLOW Yellow/blue ganglion cell Blue/yellow ganglion cell
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
Parasol system cones H ON OFF bipolars A IPL, OFF IPL, ON ON OFF ganglion cells
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 3 4 2 3 1 2 1 6 layers 4 layers midget/parasol ratio: fovea: 8 to 1 periphery: 1 to 1 fovea periphery eccentricity
Projections of the retinal ganglion cells
The central connections of the midget and parasol channels
Tissue block with injections inject blocker record V 1 V 4 MT Parvo Magno LGN?
Vl complex cell response to moving light bar Normal Parvo Injection 80-60- 40-20- Spikes per bin Magno Injection 80-60- 40-20- 80-60- 40-20- 80-60- 40-20- Paired Injection 60-40- 20- Recovery Figure by MIT OCW.
V 1 Midget Mixed V 2 Parasol w LGN P M? MT V 4 Midget Parasol PARIETAL LOBE TEMPORAL LOBE FRONTAL LOBE
Lesion studies
Behavioral procedures
Detection
Detection
Discrimination
Performance Monitor
The lesions
PERCEPTUAL FUNCTIONS TESTED Contrast Sensitivity Color Pattern Texture Shape Stereopsis Flicker Motion Brightness Scotopic Vision
Contrast sensitivity
Contrast Sensitivity 0.1 0.2 0.3 Contrast 0.4 Normal MLGN Lesion 0.5 PLGN Lesion 0.6 0.7 0.8 0.9 1 1.5 2 2.5 3 Spatial Frequency (cy/deg) Figure by MIT OCW.
Color vision
100 90 80 Color Discrimination Seneca Percent Correct 70 60 50 40 30 20 10 0 Normal PLGN MLGN Figure by MIT OCW.
Brightness perception
The perception of brightness in photopic vision 100 100 90 90 nt C o rrect 80 70 60 50 Normal 80 70 60 50 Normal rce 40 40 Pe 30 20 Parvo lesion 30 20 Magno lesion 10 10 10 20 30 50 70 10 20 30 50 Percent Luminance Contrast
Pattern and texture perception
Texture and Pattern Discrimination Percent Correct 100 90 80 70 60 50 40 30 20 10 N P M Texture N P M Pattern Figure by MIT OCW.
Stereoscopic depth perception
Stereoscopic depth perception Parvo lesion 100 Magno lesion 100 90 Percent Correct 90 80 70 60 50 40 30 20 10 Normal Parvo Lesion 80 70 60 50 40 30 20 10 Magno Lesion Normal 6.6 13.2 19.8 10 15 20 25 30 Disparity in minutes
Motion perception
Motion detection
Motion detection
Motion detection
Motion detection 100 Parvo lesion 100 Magno lesion 90 80 90 80 Normal Percent Correct 70 60 50 40 30 20 10 Normal Parvo Lesion 70 60 50 40 30 20 10 Magno Lesion 15 20 30 40 50 60 Percent Contrast 20 30 50 70
The perception of flicker
Flicker perception 100 Parvo lesion 100 Magno lesion Percent Correct 90 80 70 60 50 40 30 20 10 Normal Parvo lesion 90 80 70 60 50 40 30 20 10 Normal Magno lesion 0 5 8 11 14 17 20 23 26 5 10 15 20 25 Flicker Rate (cy/sec)
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
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
Spatial Frequency H Processing Capacity L L Midget System Parasol System H Temporal Frequency H L L H Figure by MIT OCW.
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 1. 5. 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.
Recording in V4 Magno Block Parvo Block 46 36 Before Block 46 36 After Block 0 1593 0 1589 Time (msec) Time (msec) Figure by MIT OCW.
Recording in MT Magno Block Parvo Block Before Block 59 179 After Block 59 179 0 963 0 963 Time (msec) Time (msec) Figure by MIT OCW.
1.0 0.8 Average blocking index 0.6 0.4 0.2 0.0 V4 MT Parvocellular Block Magnocellular Block Figure by MIT OCW.
V 1 Midget Mixed V 2 Parasol w LGN P M Midget Parasol
How selective are individual horizontal cells in their connections with cones? Model 1 Model 2
V 1 V 2 w LGN P M MT V 4 Midget Parasol PARIETAL LOBE TEMPORAL LOBE FRONTAL LOBE
stripes: thin inter thick V 2 V 1 1 2 3 4Ca 4Cb parasol midget 500
The blue/yellow koniocellular system cones ON OFF? ON OFF OFF ON bipolars outer IPL inner IPL yellow blue ganglion cells