1. Seeing READING ASSIGNMENT Discussion of Gregory’s Article on Visual Illusions – Tues Feb 17 Available in your course pack

2. What kind of energy does the visual system sense and perceive? The Visual System

3. Light is an oscillation (a wave) in the electromagnetic field Light

4. What are some characteristics of light waves? Properties of light

5. What are some characteristics of light waves? –amplitude/intensity - how big of a fluctuation in the field/how many waves –frequency - how many fluctuations (waves) pass by a certain point in a given period of time –polarization - the orientation of the waves Properties of light

6. What perceptions are associated with those physical properties? Properties of light

7. What perceptions are associated with those physical properties? –Intensity is associated (loosely) with brightness –Frequency is associated (loosely) with color –Polarization isn’t sensed by humans (but it is by some insects and birds!) Properties of light

8. Light The spectrum is the range of frequencies of electromagnetic waves

9. The eye –curved cornea –lens –retina –fovea –optic disk Using Light

10. Light is focused on the retina by the curvature of the cornea and the lens –Flat lens (relaxed muscles) focuses distant points Using Light

11. Light is focused on the retina by the curvature of the cornea and the lens –Accomodation: Bulged lens (muscles flexed) focuses on near points Using Light

12. Light is focused on the retina by the curvature of the cornea and the lens Constriction of the pupil limits how much light gets in AND reduces the amount of focusing required of the lens Using Light

13. photoreceptors transduce incoming light ganglion cells send signals along to the brain The Retina has layers of cells

14. 2 types of photoreceptors: rods and cones rods are very sensitive - useful in dim light Two kinds of Photoreceptors

15. Rods and cones are distributed differently across the retina The Retina

16. visual acuity (ability to see detail) depends on cones - thus acuity varies across the visual field The Retina

17. Why don’t you notice your blind spot? The Retina

18. Why don’t you notice your blind spot? –Blindspots don’t overlap! –Your brain “fills in” the missing information –The specific information in the blindspot isn’t much more missing than the rest of the periphery! The Retina

19. three types of cones: short, medium, and long different absorptions enable color vision The Retina

20. each ganglion cell integrates information from a particular spot on the retina called its receptive field Neurons “collect” information

21. Receptive Fields Stimulus is in receptive field Stimulus is near receptive field Stimulus is outside receptive field Action potentials

22. Ganglion cells project to the brain via the optic nerve information is projected to contralateral cortex! Visual Pathways