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The Incredible Journey of Vision: From Light to Perception

Explore the fascinating process of human vision, from gathering light to neural processing, and discover the complexities of color perception, eye anatomy, and common vision impairments. Uncover the mysteries of parallel processing, color theories, and intriguing phenomena like color blindness and face blindness.

jenniferwmartinez
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The Incredible Journey of Vision: From Light to Perception

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  1. Vision Module 18

  2. Human’s most dominating sense • If multiple senses are competing, vision will overwhelm the others • baby

  3. Vision Step One: Gathering Light • Light is reflected off objects • Gathered by eye • Light is small part of electric spectrum • Video

  4. Perception of Color • Depends on • Light intensity – height of wave – brightness • Light wavelength – hue or color • Objects appear as color of the wavelengths they reflect • Red shirt reflects red light and absorbs all other colors

  5. Differing Eyes Bee detects reflected ultraviolet wavelengths

  6. Vision Step Two: Within the Eye

  7. The Eye • Cornea • Outer transparent coating • protects the eye • focuses incoming light • Very sensitive

  8. The Eye • Pupil • Adjustable opening in the center of the eye • Lets light in • Iris • Ring of muscle that forms the colored portion of the eye around the pupil • Controls the size of opening allowing various degrees of light in

  9. Just FYI • Iris does not have enough time to close and adjust…shines to the back of the eye…showing blood vessels and tissue at the back of the eye called the retina

  10. The Eye • Lens • Transparent structure behind the pupil • Changes shape through accomodation to focus images on the retina • Cataracts are the clouding of the eye’s lens • Hold up one finger and focus on it. Now look at wall. Now back to finger.

  11. The Eye • Accommodation • Change in the curvature of the lens that enables the eye to focus on objects at various distances

  12. Vision Impairments • Myopia • Nearsightedness • Can’t see far away objects as well • Hyperopia • Farsightedness • Decreased vision for up close objects

  13. Vision Step Three: Transduction • Translation of incoming stimuli into neural signals • Occurs when light activates the neurons in the retina

  14. Transduction

  15. The Eye • Retina • Light-sensitive membrane at the back of the eye • Contains millions of photoreceptors for vision • Begins the processing of visual information

  16. Photoreceptors • Rods • More sensitive to light • Peripheral retina • Detect black, white, and gray • Twilight or low light • Cones • Near center of retina – mainly in the fovea • Fine detail and color vision • Daylight or well-lit conditions

  17. The Retina • Light energy rods and cones bipolar cells  ganglion cells • Bipolar cells • Collect neural signals from rods and cones • Transfer messages to ganglion cells • Ganglion cells • Organize the neural signals • Axons converge into optic nerve

  18. Receptors in the Human Eye Cones Rods Number 6 million 120 million Location in retina Center Periphery Sensitivity in dim light Low High Color sensitive? Yes No

  19. Blind Spot • Point where blood vessels and nerves exit the eye • No rods or cones

  20. The Eye • Optic Nerve • Nerve that carries neural impulses to the brain • Dissection Video

  21. Vision to the brain • Optic Nerve then carries the neural signals to the primary visual cortex • Optic chiasm (Ki-asm) crosses to opposite hemisphere of the brain • Info is transferred to the thalamus where it is relayed to the visual cortex in the occipital lobes

  22. Vision from the Eye to the Brain

  23. Visual Information Processing • Feature Detectors • David Hubel and Torsten Wiesel • Located in the visual cortex • nerve cells in the brain that respond to specific features • Shape • Angle • Movement • Sam I Am

  24. Visual Information Processing • Parallel Processing • Processing of several aspects of an object simultaneously • Crash Course

  25. Color Theories • Young-Helmholtz trichromatic theory • Three types of cone cells – red, green and blue • All other colors are perceived through the mixing of signals from cones

  26. Color Blindness • Most common • Partial color blindness • Lacks either red or green cones – red and green look like the same color • More common in males • NFL color rush • game

  27. Opponent Process Theory • Two color process • Opposing pairs • Red – green • Yellow – blue • Explains a phenomena known as afterimages • Afterimage – visual experience that occurs after the original source of stimulation is no longer present • flag • video

  28. Prosopagnosia • Face Blindness • video

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