Rozi Xu & Daniil Kolesnikov VISION Light Energy Neural Messages Transducing Into Rozi Xu & Daniil Kolesnikov

Determining our Sensory Experience of Light WAVELENGTH: the distance from the peak of one light or sound wave to the peak of the next determines hue HUE: the dimension of color; what we know as the color names blue, green, and so forth

Determining our Sensory Experience of Light AMPLITUDE: height of a wavelength INTENSITY: the amount of energy in a light or sound wave; what we perceive as brightness or loudness

The Eye

Structure of an Eye Shark corneas have been used in place of human corneas before! protects the eye and bends light to provide focus the light-sensitive inner surface of an eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information When we’re attracted to someone, our pupils dilate as much as 45%! ACCOMMODATION: the process by which the eye’s lens changes shape to focus near/far objects on the retina 1 the adjustable opening in the center of the eye through which light enters 4 Retina’s area of central focus the transparent structure behind the pupil that changes shape to help focus images on the retina 5 2 8 Blind Spot 6 The point at which the optic nerve leaves the eye (no receptor cells here) Our irises have over 256 different characteristics; fingerprints only have 40. 3 a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening Carries neural impulses from eye to brain 7

Retina Processing Retinal receptors that are concentrated near the center of the retina and that function in daylight or in well-light conditions. Detect fine detail and give rise to color sensations. Blind Spot Retinal receptors that detect black, white, & gray; necessary for peripheral and twilight vision, when cones don’t respond. Can send nearly 1 million messages at once through its nearly 1 million ganglion fibers

Rods and Cones Located in the periphery of retina Share bipolar cells with other rods, sending combined messages Enable black-and-white vision Sensitive to faint light 120 million rods Cluster in and around the fovea (center of retina) Each one transmits to a single bipolar cell that helps relay the cone’s individual message to the visual cortex These direct “hotlines” preserve cones’ precise information Enable you to perceive color Sensitive to detail & color 6 million cones

Visual Information Processing 1 3 4 2

Feature Detection

Parallel Processing

Review SiR, FaceuP Right SCENE Brain’s detector cells respond to specific features → edges, lines, and angles Brain interprets the constructed image based on information from stored images SiR, FaceuP Right SCENE RETINAL PROCESSING FEATURE DETECTION PARALLEL PROCESSING RECOGNITION Brain cell teams process combined information about motion, form, depth, and color Receptor rods and cones → bipolar cells → ganglion cells

Color Vision Young Helmholtz Trichromatic (three color) theory: the theory that the retina contains three different color receptors: one most sensitive to red, one most sensitive to green, one most sensitive to blue. Every color we “see” is a combination of red, green, and/or blue. Color-deficient vision lacks functioning red- and/or green-sensitive cones. Vision becomes monochromatic or dichromatic. Afterimages: Ex.: When you stare at something that’s green, look at a white piece of paper, and see red Hering’s opponent-process theory: the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision Ex.: In the thalamus, some neurons are turned “on” by red but turned “off” by green

Some Popular Optical Illusions

What do you see?

What is it actually? HAPPY HALLOWEEN! The Thatcher Effect Our brains can’t process faces upside down. Our brains are programmed to recognize faces by creating a mental map in pieces (eyes, mouth, nose, etc.). Therefore, when we encounter a Thatcherized face, we assume that because the facial features look fine, the rest of the face is as well.

What do you see?

What is it actually? Silhouette Illusion Due to the lack of depth/width cues, it is possible to see the dancer moving BOTH counterclockwise and clockwise. It comes from our brains trying to reconstruct a 3D space from the flat image that is given to us. The brain adds information that is realistic, but not really there.

What do you see?

What is it actually? Deception on your Perception

What do you see?