1. 1 Psychology 304: Brain and Behaviour Lecture 31

2. 2 Announcement “Body Worlds and the Brain is now at Science World at TELUS World of Science for a limited time. This all-new version of Dr. Gunther von Hagens’ world-famous exhibition looks at the body in a previously unseen way! With over 200 authentic human specimens, and highlights on recent neuroscience findings on brain development, function and disease, it will excite even those guests who visited when we hosted BODY WORLDS 3 in 2006.”

3. 3 From last class ….

4. 4 Olfactory Receptors and Pathways of the Olfactory System Olfactory Epithelium

5. 5 Pathways of the Olfactory System Secondary olfactory cortex

6. 6 The Visual System 2. What is the structure of the eye and where are the receptors for light? 1. What are the physical and perceptual dimensions of light?

7. 7 By the end of today’s class, you should be able to: 2. describe the structural and functional features of the eye ball and retina. 1. describe the three physical and three perceptual dimensions associated with light. 3. distinguish between cones and rods.

8. 8 Light waves vary on three physical dimensions. Each physical dimension uniquely influences our perception of colour. What are the physical and perceptual dimensions of light?

9. 9 1. Wavelength  Determines hue.  Relatively long wavelengths: Yellow/red hue. Relatively short wavelengths: Blue/purple hue.

10. 10 A Wavelength

11. 11 Wavelengths Associated with Distinct Hues

12. 12  The human eye is only capable of detecting light with a wavelength of 380 – 760 nanometers.

13. 13 Wavelengths and Colours Visible to the Human Eye

14. 14  Determines brightness (i.e., light vs. dark). 2. Intensity  Greater number of light waves of a given wave- length: bright. Fewer number of light waves of a given wave- length: dark.

15. 15 Hue vs. Brightness

16. 16  Determines saturation. 3. Purity  One wavelength: saturated hue. Many wavelengths: intermediate hue. All wavelengths: no hue (white)

17. 17 Saturation Brightness Saturation vs. Brightness

18. 18 The Perceptual Properties of Colour

19. 19 What is the structure of the eye and where are the receptors for light? Light waves pass through the cornea, pupil, and lens of the eye, ultimately falling on the retina, the interior lining of the back of the eye.

20. 20 Vitreous humor The Human Eye

21. 21 The retina is composed of five layers of different types of neurons: receptors, horizontal cells, bipolar cells, amacrine cells, and retinal ganglion cells. Light reaches the receptor layer only after passing through the other four layers; for this reason, the cellular organization of the retina is described as “inside-out.” The point at which the optic nerve exits the eye is referred to as the optic disc and produces a “blind spot” in the visual field.

22. 22 The Cellular Structure of the Retina

23. 23 A Section of the Retina

24. 24 A Section of the Retina and Optic Nerve

25. 25 Cones allow for high visual acuity because a single ganglion cell receives input from only one or a few cones (low convergence). Rods allow for high sensitivity to illumination because a single ganglion cell receives input from many rods (high convergence). There are two types of receptors in the human retina: cones and rods.

26. 26 Convergence of Cones and Rods on Retinal Ganglion Cells

27. 27 The Visual System 2. What is the structure of the eye and where are the receptors for light? 1. What are the physical and perceptual dimensions of light?