1. THE VISUAL SYSTEM

2. LIGHT Electromagnetic radiation that travels as a wave Amplitude = brightness Wavelength = color Varies in purity (richness of colors)

3. THE EYE Light enters through cornea Cornea and lens form an upside down image Lens: transparent eye structure that focuses the light rays falling on the retina

4. VISUAL DEFICIENCIES Nearsighted: close objects are clear; far objects are blurry Caused by light from far objects falling short of retina Farsighted: distant clear; close blurry Caused by light from close objects falling behind retina and eyeball being too short

5. EYE Iris: colored ring of muscle surrounding the pupil Pupil: opening in the center of iris that helps regulate the amount of light passing into the rear chamber of the eye

6. RETINA: BRAINS ENVOY TO THE EYE Retina: neural tissue lining the inside back surface of the eye; it absorbs light, processes images, and sends visual info. to the brain Optic disk: a hole in the retina where optic nerve fibers exit the eye

7. RODS AND CONES Cones: specialized visual receptors that play a key role in daylight vision and color vision Fovea: tiny spot in center of retina; contains only cones Rods: play key role in night vision and peripheral vision

8. DARK AND LIGHT ADAPTATION Dark adaptation: process in which the eyes become more sensitive to light in low illumination Light adaptation: eyes become more sensitive to light in high illumination

9. INFO PROCESSING IN THE BRAIN Light hits receptors; triggers neural signals Signals move to optic nerve Receptive field of visual cell: the retinal area that, when stimulated affects the firing of that cell

10. VISUAL PATHWAYS TO THE BRAIN Optic chiasm: pt at which the optic nerves from the inside half of each eye cross over and then project to the opposite half of the brain Optic fibers then diverge along 2 paths Main path projects into thalamus; retinal axons synapse in the Lateral geniculate nucleus (LGN) Then to the occipital lobe to the primary visual cortex Main path divided into 2 paths: magnocellular and parvocellular channels---engage in parallel processing 2 nd path goes to Superior colliculus in the midbrain

11. INFO PROCESSING IN VISUAL CORTEX Feature detectors: neurons that respond selectively to very specific features of more complex stimuli Visual agnosia: inability to recognize objects Prosopagnosia: inability to recognize familiar faces