March 1 Table of Contents: 77. March 1 & 2 78. Vision Book Agenda: 1. Daily Sheet 2. Vision Notes and Discussion 3. Work on vision book! EQ- How does vision work? Do Now 1.Find your Vision Sensation fill-in-theblanks note page. (you completed this last week for homework) 2.What is the difference between sensation and perception? 3.What are five major parts of the eye? HW- Finish your vision book!
Jot these down on your daily sheet! The Seven Senses Sense Sight Hearing Smell Taste Touch Balance (vestibular) Body Awareness (proprioception) Sensory Organ Eyes Ears Nose Mouth Skin Inner Ear Muscles and Joints
Vision
Transduction In sensation, the transformation of stimulus energy into neural impulses (light=sight, sound=hearing, chemicals=smell and taste.) Phototransduction: Conversion of light energy into neural impulses that the brain can understand.
Both Photos: Thomas Eisner The Stimulus Input: Light Energy What strikes our eyes is not color but electromagnetic energy We have a very small spectrum that we can see- called the visible spectrum Visible Spectrum
What makes up a light wave? 1. Wavelength (hue/color) 2. Intensity (brightness)
Wavelength The distance from the peak of one light wave to the peak of the next. The distance determines the hue (color) of the light we perceive.
Wavelength (Hue) Violet Indigo Blue Green Yellow Orange Red 400 nm 700 nm Short wavelengths Long wavelengths Different wavelengths of light result in different colors.
Intensity The amount of energy in a light wave. Determined by the height of the wave. The higher the wave the more intense the light is.
Intensity (Brightness) Intensity Amount of energy in a wave determined by the amplitude (height). It is related to perceived brightness.
Intensity (Brightness) Blue color with varying levels of intensity. As intensity increases or decreases, blue color looks more washed out or darkened.
The Eye
Parts of the eye 1. Cornea: Transparent tissue where light enters the eye, also responsible for protecting the eye 2. Iris: colored muscle that expands and contracts to change the size of the opening (pupil) for light. (also changes with our emotions!) 3. Lens: Focuses the light rays on the retina (projects an upside down image through a process called accommodation) 4. Retina: tissue on the inner surface of the ear; contains sensory receptors that process visual information and sends it to the brain.
The Lens Lens: Transparent structure behind the pupil that changes shape to focus images on the retina. Accommodation: The process by which the eye s lens changes shape to help focus near or far objects on the retina. Nearsightedness: focuses before the image (far away objects are blurry) Farsightedness: focuses beyond the image (close objects are blurry)
Optic Nerve & Blind Spot Optic nerve: Carries neural impulses from the eye to the brain. Blind Spot: Point where the optic nerve leaves the eye because there are no receptor cells located there. This creates a blind spot. Test your blind spot!
Photoreceptor cells- millions located on the retina; transduction occurs here Rods Located in the periphery of the retina 120 million Allow you to see in black and white Work well in dim light Don t see a lot of detail Cones Located in and around the fovea (the retina s center area for focus) Around 6 million Allow you to see color Don t work well in dim light Allow you to see in high detail
How does vision work? Light comes into the outer layer of the retina Triggers chemical change that sparks neural signals and activates bipolar cells Bipolar cells then activate ganglion cells Axons in the ganglion cells then form optic nerve that carries info to the thalamus and then to the visual cortex in the optic nerve Optic nerve can send 1 million message at a time though its 1 million ganglion fibers
Visual Information Processing Optic nerves connect to the thalamus in the middle of the brain, and the thalamus connects to the visual cortex.
Theory Feature Detection Parallel Processing Color Vision Young-Helmholtz trichromatic theory Notes Visual Perception Color Deficient Opponent Process Theory Afterimage
Feature Detection Nerve cells in the visual cortex respond to specific features, such as edges, shapes, lines, angles, and movement. For really complex stimuli- pass on to other areas of the cortex Ex: Faces: area in the temporal lobe behind the right ear
From Sensation to Recognition Tim Bieber/ The Image Bank
Parallel Processing The processing of several aspects of a problem simultaneously. Color Motion Form Depth
Visual Information Processing Processing of several aspects of the stimulus simultaneously is called parallel processing. The brain divides a visual scene into subdivisions such as color, depth, form and movement etc.
How do we see in color? What color is this dragon?
Trichromatic (three color) Theory Created by Hemholtz There are three primary colors- Any other color is created by combining light waves of these three So they guessed that we have 3 different types of receptor cells in our eyes. Together they can pick any combination of our 7 million color variations. Most colorblind people simply lack cone receptor cells for one or more of these primary colors.
Color Blindness- usually caused by a cone deficiency Genetic disorder in which people are blind to certain colors. Most common is green-red. This supports the Trichromatic theory. Ishihara Test
Opponent Process Theory Hering proposed that our ganglion cells process colors in opposing pairs of red-green, blue-yellow, and blackwhite. Cones Retinal Ganglion Cells
Opponent Colors- Afterimage When we stare at something for too long, the cones associated with that color will tire- and its partner color will be activated Gaze at the middle of the flag for about 30 Seconds. When it disappears, stare at the dot and report whether or not you see Britain's flag. See p. 84 in the high school book for the same idea with the American flag
Your Vision Book On the cover: Give it a title, your name, # and a picture Page 1: Diagram of the eye- labelled with the main parts of the eye defined Page 2: Venn Diagram comparing and contrasting Rods and Cones Page 3: Create a list of steps for HOW vision works Start with: Light waves from the image enter the cornea. End with: The neural message is sent to the thalamus and then to the occipital lobe. Page 4: Chart on Visual perception theories