Visual Sensory Systems - Lesson 3 PDF

Visual Sensory System Lochness monster or tree branch? What is the cornea? -clear, protective outer layer covering the pupil and iris -light enters the eye through the cornea What is the pupil? -small, adjustable opening in the center of the eye -light passes through the pupil What is the iris?...

Visual Sensory System Lochness monster or tree branch? What is the cornea? -clear, protective outer layer covering the pupil and iris -light enters the eye through the cornea What is the pupil? -small, adjustable opening in the center of the eye -light passes through the pupil What is the iris? -pigmented muscle that gives the eye its color -controls the size of the pupil by expanding/contracting over it What is the lens? -transparent structure behind the pupil that changes shape –helps the retina focus on images What is the retina? -light-sensitive inner surface in the back of the eye -curvature of eye’s surface projects flipped images onto the retina -receptor cells What is the fovea? -central focal point in the retina -greatest area of visual activity; responsible for sharpness and color vision Converting light into vision: 1. Incoming light waves reach the receptor cells in the retina’s outer layer Receptor Cells Rods: Photoreceptor cells that… detect black, white and grey sensitive to movement peripheral and night vision/low lighting located along the retina Cones: Photoreceptor cells that… Detect fine detail and color day-time/bright lighting located around the fovea What is the optic nerve? -bundle of neurons Converting light into vision: 2. Light activates chemical and electrical processes in ganglion and bipolar cells, which convert light into signals 3. The optic nerve sends signals to the thalamus and occipital lobes 4. The brain processes the signals to create a visual image What is the blind spot? -point where the optic nerve leaves the eye due to no receptor cells The Visual In the visual cortex, the brain begins working by transforming neural impulses into visual Cortex sensations of color, form, boundary and movement… this is called parallel processing  Theories of Color Vision: Young-Helmholtz Theory Opponent-Process Theory Young- Helmholtz Theory Also known as trichromatic color theory Color vision is a function of our cones… three primary colors: red, green, blue Color Blindness a defective cone results in color vision errors called color blindness “colorblind” people see colors, but their color perception is limited and inaccurate… Trichromats All cones are present Normal color vision Dichromats have two cone systems unable to see primary color of missing cone, creating a reduced color spectrum Monochromats complete color blindness have on cone system: can see shades of grey red-green color The photo on the left shows how people blindness affects with red-green deficiency perceived a 2015 Buffalo Bills vs. New York Jets football 99% of people game. “Everyone looks like they’re on the same with color team” said one color-blind fan. The photo on the right shows how the blindness… game looked for those with normal color vision. MATCH THE PICTURE TO THE TERM: Dichromat Monochromat Trichromat Monochro Dichroma Trichro mat t mat Ishihara Charts Ishihara Charts  Cones are linked in opposing pairs red-green, blue-yellow, and black-white Have you ever seen a color that wasn't quite blue, Opponent- but wasn't quite green—a bluish-green? Sure you have. That's because the cones for blue and green Process are not opposing pairs; they are able to fire at the same time. Theory Have you ever seen a color that's sort of green and sort of red? No, there is no green-red, they are opposing pairs / complementary colors. Only one of them can be firing at a time. You can see blue and red together, or blue and green together, but not green and red. After Image Staring at an image for 30-60 seconds causes opponent cells to become fatigued and briefly de-active, allowing for opposing cells to fire in response