1. PSYCH 2220 Sensation & Perception I Lecture 3

2. Keywords for lecture 2 Air-dwelling eye, water-dwelling eye, (both: mask, powerful lens, flat cornea, pinhole), presbyopia, astigmatism, accommodation, depth of focus, ophthalmoscope, retina, retinal blood vessels, fovea, optic disk, blind spot, retina, cells, cell membrane, ions, potassium, sodium, channels (meaning 1), neurones, resting potential (-70mV), action potential, synapse, neurotransmitter, Schwann cells, axon, dendrites, polarization, depolarization, hyperpolarization, dark/light adaptation, rods, thresholds, sensitivity, cones, visual purple, Purkinje shift, scotopic, photopic, fovea, receptive fields, bipolar cells, retinal ganglion cells

3. Eye movements Point eyes to right place Accommodation focus Pupils Light Adaptation Adjust for the light level Transduction Convert light energy to activity in cells

5. Optic Disc Fovea

6. The foveal pit

8. RETINAL GANGLION CELLS

9. Bipolar cell CONVERGENCE ….. which means the receptive field of a RGC is bigger than a photoreceptor

10. Bipolar cell DIVERGENCE ….. which means the receptive fields of RGCs overlap.

11. Excitatory Bipolar cell Inhibitory Bipolar cell receptive field spontaneous activity

12. Excitatory Bipolar cell Inhibitory Bipolar cell OFF-CENTRE CELL

13. Excitatory Bipolar cell Inhibitory Bipolar cell

14. Excitatory Bipolar cell Inhibitory Bipolar cell ON-CENTRE CELL

17. VIDEO from disc… Look at how the cells will respond to an edge. Followed by Sustained and Transient

18. video...

19. response 1 2 21 3 3 4 4 5 5 space response to spot in centre response to spot in surround spontaneous level 0 high low LIGHT DARK

20. Mach bands

21. HI !

23. Types of Retinal Ganglion Cells On-centre Off-surround Off-centre On-surround SustainedtransientSustainedtransient 1 2 3 4

24. Perceptual effects that can be understood from knowing about retinal ganglion cells...

25. Mach bands

26. Simultaneous contrast

28. Scallop illusion

29. Scallop illusion luminance

31. A light check in the shadow is the same gray as a dark check outside the shadow. ©1995, Edward H. Adelson

32. PHYSICAL PERCEPTUAL luminancebrightness wavelengthcolour

33. Hermann Grid

34. less inhibition

36. RETINAL GANGLION CELLS Have spontaneous activity show action potentials can be inhibited by light can be excited by light have concentric fields have smaller fields in the fovea (they also respond in an interesting and surprising way to colour, but we’ll come back to that when we look at colour)

37. INFORMATION GOING TO BRAIN is LIMITED (partial) is ALREADY PROCESSED is in the form of ACTION POTENTIALS is DISTORTED (fovea more) tells about EDGES (change)

38. Introduction to the structure of the brain

44. Cortex

58. Lateral geniculate nucleus of the THALAMUS

59. Organization of the lateral geniculate of the THALAMUS (1) Parvocellular layers (3- 6) Magnocellular layers (1- 2)

60. Injection of tracer to left eye 6 5 4 3 2 1 1 2 3 4 5 6

62. CORTEX

64. Magnification factor when looking at the centre, each letter uses the same amount of cortex

65. David HubelTorsten Wiesel Plotting the receptive field of a simple cell…..

66. Hubel & Wiesel described three types of cells in the cortex: simple complex hypercomplex from their responses all vision is built up. They received a NOBEL PRIZE for this work.

68. SIMPLE CELLS are orientation tuned...

69. Complex cells