Review, the visual and oculomotor systems

Transcription

1 The visual and oculomotor systems Peter H. Schiller, year 2013 Review, the visual and oculomotor systems 1

2 Basic wiring of the visual system 2

3 Primates Image removed due to copyright restrictions. Please see lecture video or Figure 3 from Schiller, Peter H., and Edward J. Tehovnik. "Visual prosthesis." Perception 37, no. 10 (2008):

4 Retina and LGN 4

5 sign inverting synapse sign conserving synapse pigment epithelium rods photo- receptors cones Bipolar glutamate receptors: ON = mglur6 OFF = mglur 1 & 2 OPL gap junction cone horizontal H ON OFF bipolars ON glycinergic synapse IPL AII ON OFF amacrine ganglion cells incoming light to CNS 5

6 Coronal section of monkey LGN fovea Figure removed due to copyright restrictions periphery layers 4 layers Please see lecture video or Figure 4A of Schiller, Peter H., and Edward J. Tehovnik. "Visual Prosthesis." Perception 37, no. 10 (2008): midget/parasol ratio: fovea: 8 to 1 periphery: 1 to 1 midget parasol fovea periphery eccentricity 6

7 Visual cortex 7

8 MEP Central Sulcus MIP LIP STS FEF V1 Principalis Arcuate V4 Lunate Image by MIT OpenCourseWare. 8

9 Cortical projections from LGN K1 M P K V1 Lamina: 3-6 = parvo 1-2 = magno interlaminar LGN Pion Ltd. and John Wiley & Sons, Inc.. All rights reserved. This content is excluded from our Creative Commons license. For more information, see 9

10 Transforms in V1 Orientation Direction Spatial Frequency Binocularity ON/OFF Convergence Midget/Parasol Convergence 10

11 Three models of columnar organization in V1 11 Original Hubel-Wiesel "Ice-Cube" Model Cortical Left Eye Right Eye Midget Parasol Sub-cortical Radical Model 1 mm Left Eye Right Eye Swirl Model Image by MIT OpenCourseWare.

12 Striate Cortex Output Cell Intracortical LEFT EYE INPUT Midget ON Midget OFF Parasol ON Parasol OFF Midget ON Midget OFF Parasol ON Parasol OFF RIGHT EYE INPUT luminance color orientation spatial frequency depth motion 12

13 Extrastriate cortex 13

14 MEP Central Sulcus MIP LIP STS FEF V1 Principalis Arcuate V4 Lunate Image by MIT OpenCourseWare.

15 Major cortical visual areas: Occipital V1 V2 V3 V4 MT (medial temporal) Temporal IT (inferotemporal) Parietal LIP (lateral intraparietal) VIP (ventral intraparietal) MST (medial superior temporal) Frontal FEF (frontal eye fields) 15

16 The ON and OFF Channels 16

17 The receptive fields of three major classes of retinal ganglion cells ON inhibition OFF inhibition ON/OFF inhibition 17

18 Action potentials discharged by an ON and an OFF retinal ganglion cell Figure removed due to copyright restrictions. Please see lecture video or Figure 2A of Schiller, Peter H., and Edward J. Tehovnik. "Visual Prosthesis." Perception 37, no. 10 (2008):

19 The 2-amino-4-phosphonobutyrate (APB) experiments blocking the ON channel: 1. No effect on center-surround antagonism and on orientation and direction selectivities in V1. 2. Deficit in detecting light increment but not light decrement. 19

20 The central conclusion: The ON and OFF channels have emerged in the course of evolution to enable organisms to process both light incremental and light decremental information rapidly and effectively. 20

21 The midget and parasol channels 21

22 MIDGET SYSTEM PARASOL SYSTEM Neuronal response profile ON OFF ON OFF time 22

23 Projections of the midget and parasol systems V 1 Midget Mixed V 2 Parasol w LGN P M? MT V 4 Midget Parasol PARIETAL LOBE TEMPORAL LOBE 23

24 Summary of PLGN and MLGN lesion deficit magnitudes VISUAL CAPACITY PLGN MLGN color vision severe none texture perception severe none pattern perception fine severe none V 4 mild mild mild MT none none none INTERMEDIATE BASIC VISUAL FUNCTIONS shape perception brightness perception coarse scotopic vision contrast sensitivity stereopsis motion perception flicker perception choice of "lesser" stimuli visual learning object transformation fine coarse fine coarse fine coarse severe mild none none severe mild severe pronounced none none severe not tested not tested none none none none none none none none moderate severe none not tested not tested mild none none none mild none none none none none severe severe pronounced none none none none mild mild none none moderate pronounced none none not tested 24

25 H Spatial Frequency The midget system extends the range of visual processing in the spatial frequency and wavelength range. Processing Capacity L L Midget System Parasol System H Temporal Frequency H The parasol system extends the range of visual processing in the temporal frequency range. L L H Image by MIT OpenCourseWare. 25

26 Color vision and adaptation 26

27 The color circle Y Hue G Saturation R B Image by MIT OpenCourseWare. 27

28 Basic facts and rules of color vision 1. There are three qualities of color: hue, brightness, saturation 2. There is a clear distinction between the physical and psychological attributes of color: wavelength vs. color, luminance vs. brightness. 3. Peak sensitivity of human photoreceptors (in nanometers): S = 420, M = 530, L = 560, Rods = Grassman's laws: 1. Every color has a complimentary which when mixed propery yields gray. 2. Mixture of non-complimentary colors yields intermediates. 5. Abney's law: The luminance of a mixture of differently colored lights is equal to the sum of the luminances of the components. 6. Metamers: stimuli producing different distributions of light energy that yield the same color sensations. 28

29 Response to Different Wavelength Compositions in LGN Blue ON cell Yellow ON cell Spikes per Second Green OFF cell Red ON cell maintained discharge rate

30 Response of a retinal ganglion cell at various background adaptation levels 400 Discharge rate (spikes/sec) background log cd/m Test flash (log cd/m 2 ) Image by MIT OpenCourseWare. 30

31 Basic facts about light adaptation 1. Range of illumination is 10 log units. But reflected light yields only a 20 fold change (expressed as percent contrast). 2. The amount of light the pupil admits into the eye varies over a range of 16 to 1. Therefore the pupil makes only a limited contribution to adaptation. 3. Most of light adaptation takes place in the photoreceptors. 4. Any increase in the rate at which quanta are delivered to the eye results in a proportional decrease in the number of pigment molecules available to absorb those quanta. 5. Retinal ganglion cells are sensitive to local contrast differences, not absolute levels of illumination. 31

32 Depth perception 32

33 Cues used for coding depth in the brain Oculomotor cues Visual cues accommodation vergence Binocular stereopsis Monocular motion parallax shading interposition size perspective 33

34 Autostereogram Image removed due to copyright restrictions. Please see lecture video or the autostereogram from The Magic Eye, Volume I: A New Way of Looking at the World. Andrews McMeel Publishing, Masayuki Ito, 1970, Chris Tyler,

35 MOTION PARALLAX, the eye tracks 1 a 2 b a eye movement object motion 1 The eye tracks the circle, which therefore remains stationary on the fovea Objects nearer than the one tracked move at greater velocities on the retinal surface than objects further; the further objects actually move in the opposite direction on the retina. 2 b 35

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37 37 37

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39 Form perception 39

40 Three general theories of form perception: 1. Form perception is accomplished by neurons that respond selectively to line segments of different orientations. 2. Form perception is accomplished by spatial mapping of the visual scene onto visual cortex. 3. Form perception is accomplished by virtue of Fourier analysis. 40

41 Form perception with little information about orientation of line segments Image removed due to copyright restrictions. Please refer to lecture video. 41

42 Cortical layout of neurons activated by disks disks in one hemifield Image by MIT OpenCourseWare. 42

43 Cortical layout of neurons activated by disks disks across midline Image by MIT OpenCourseWare. 43

44 Prosthetics 44

45 Image removed due to copyright restrictions. Please see lecture video or Figure 5 from Schiller, Peter H., and Edward J. Tehovnik. "Visual prosthesis." Perception 37, no. 10 (2008):

46 Image removed due to copyright restrictions. Please see lecture video or Figure 7 from Schiller, Peter H., and Edward J. Tehovnik. "Visual prosthesis." Perception 37, no. 10 (2008):

47 Image removed due to copyright restrictions. Please see lecture video or Figure 9 from Schiller, Peter H., and Edward J. Tehovnik. "Visual prosthesis." Perception 37, no. 10 (2008):

48 Illusions 48

49 The Hermann grid illusion The most widely cited theory purported to explain the illusion: Image is in public domain. Due to antagonistic center/surround organization, the activity of ON-center retinal ganglion cells whose receptive fields fall into the intersections of the grid produces a smaller response than those neurons whose receptive fields fall elsewhere. 49

50 Differently oriented vertical and horizontal lines reduce illusion Figure removed due to copyright restrictions. Please see lecture video or Schiller PH, Carvey CE (2005). "The Hermann Grid Illusion Revisited." Perception 34 (11):

51 Retinal ganglion cell receptive field layout at an eccentricity of 5 degrees Figure removed due to copyright restrictions. Please see lecture video or Schiller PH, Carvey CE (2005). "The Hermann Grid Illusion Revisited." Perception 34 (11):

52 After-effect illusions explained by the facts and rules of adaptation. interocular experiments 52

53 Effects of lesions on vision 53

54 Summary of lesion deficit magnitudes 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 INTERMEDIATE BASIC VISUAL FUNCTIONS shape perception fine severe none mild none coarse mild none none none brightness perception none none none none coarse scotopic vision none none none none contrast sensitivity fine severe none mild mild coarse mild none none mild stereopsis fine coarse severe none none none pronounced none none none motion perception none moderate none moderate flicker perception none severe none pronounced 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 54

55 Eye-movement control 55

56 Electrical stimulation triggering eye movements: Figure removed due to copyright restrictions. Please see lecture video or Figure 2 from Schiller, Peter H., and Edward J. Tehovnik. "Look and See: How the Brain Moves Your Eyes About." Progress in Brain Research 134 (2001):

57 Electrical stimulation triggering eye movements: Figure removed due to copyright restrictions. Please see lecture video or Figure 3 from Schiller, Peter H., and Edward J. Tehovnik. "Look and See: How the Brain Moves Your Eyes About." Progress in Brain Research 134 (2001):

58 Summary of the effects of the GABA agonist muscimol and the GABA antagonist bicuculline Target selection Visual discrimination muscimol bicuculline muscimol bicuculline V1 INTERFERENCE INTERFERENCE V1 DEFICIT DEFICIT FEF INTERFERENCE FACILITATION FEF MILD DEFICIT NO EFFECT LIP NO EFFECT NO EFFECT LIP NO EFFECT NO EFFECT SC INTERFERENCE FACILITATION Hikosaka and Wurtz 58

59 Figure removed due to copyright restrictions. Please see lecture video or Figure 17 from Schiller, Peter H., and Edward J. Tehovnik. "Look and See: How the Brain Moves Your Eyes About." Progress in Brain Research 134 (2001):

60 V 1 Midget Mixed Parasol V 2?? Auditory system w LGN Midget P M Parasol w SC MT Posterior system PARIETAL LOBE BG V 4 TEMPORAL LOBE? Somatosensory system Olfactory system rate code BS BS vector code SN vector code FRONTAL LOBE FEF MEF place code Anterior system Smooth pursuit system Vergence Accessory Vestibular system optic system system 60

61 Motion perception 61

62 Summary of cell types in V1 s 1 D s 5 D L DEGREES OF VISUAL ANGLE deg L D s 2 L D DEGREES OF VISUAL ANGLE s 6 D L deg s 3 L L D deg D s 7 L D L s 4 L D deg L D L D deg CX D L deg Image by MIT OpenCourseWare. 62

63 The central role of the parasol system in motion processing and in the perception of apparent motion. 63

64 Major Pathways of the Accessory Optic System (AOS) Velocity response of AOS neurons = deg/sec Number of AOS RGCs in rabbit = 7K out of 350K 2 1 Ant Cortex Cerebellum 3 Prime axes of retinal direction-selective neurons NOT climbing fibers D M 1 Inferior Olive Semicircular canals rate code BS BS L 2,3 2,3 Terminal Nuclei Vestibular Nucleus vestibulo-ocular reflex 64

65 MIT OpenCourseWare Sensory Systems Fall 2013 For information about citing these materials or our Terms of Use, visit: