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Vision

Vision. Transduction conversion of one form of energy to another in sensation, transforming of stimulus energies into neural impulses (ex: light energy into neural messages) Wavelength the distance from the peak of one wave to the peak of the next. Hue

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Vision

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  1. Vision • Transduction • conversion of one form of energy to another • in sensation, transforming of stimulus energies into neural impulses (ex: light energy into neural messages) • Wavelength • the distance from the peak of one wave to the peak of the next

  2. Hue dimension of color determined by wavelength of light Wavelength also determines the pitch of sounds Great amplitude (bright colors, loud sounds) Short wavelength=high frequency (bluish colors, high-pitched sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Small amplitude (dull colors, soft sounds) Vision

  3. Intensity amount of energy in a wave determined by amplitude brightness loudness Great amplitude (bright colors, loud sounds) Short wavelength=high frequency (bluish colors, high-pitched sounds) Long wavelength=low frequency (reddish colors, low-pitched sounds) Small amplitude (dull colors, soft sounds) Vision

  4. The spectrum of electromagnetic energy

  5. Differing Eyes Bee detects reflected ultraviolet wavelengths

  6. Vision

  7. Vision • Pupil- adjustable opening in the center of the eye • Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening • Lens- transparent structure behind pupil that changes shape through accommodation to focus images on the retina

  8. Vision • Accommodation- the process by which the eye’s lens changes shape to help focus near or far objects on the retina • Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information

  9. Vision • Acuity- the sharpness of vision (can be affected by distortions in the eye’s shape) • Nearsightedness- condition in which nearby objects are seen more clearly than distant objects because distant objects in front of retina • Farsightedness- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina

  10. Vision • Normal Nearsighted Farsighted Vision Vision Vision

  11. Myopia Simulation

  12. How do we correct vision? • Glasses, contact lenses, or LASIK surgery reshape the cornea (which is also involved in bending light to provide focus) to correct the problem

  13. Retina’s Reaction to Light • Optic nerve- nerve that carries neural impulses from the eye to the brain • Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there • Fovea- central point in the retina, around which the eye’s cones cluster

  14. Blind Spot

  15. Retina’s Reaction to Light- Receptors • Rods • peripheral retina • detect black, white and gray • twilight or low light • Cones • near center of retina • fine detail and color vision • daylight or well-lit conditions • Light energy striking the rods and cones produces chemical changes that generate neural signals

  16. 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 Vision- Receptors

  17. Light energy  Rods and Cones  Bipolar Cells  Ganglion Cells (axons form the optic nerve)

  18. Pathways from the Eyes to the Visual Cortex

  19. Cell’s responses Stimulus Visual Information Processing • Feature Detectors • Located in the visual cortex • nerve cells in the brain that respond to specific features • shape • angle • movement

  20. How the Brain Perceives

  21. Illusory Contours

  22. If the region responsible for perceiving faces were damaged, you would have difficulty recognizing familiar faces

  23. Visual Information Processing • Parallel Processing • simultaneous processing of several aspects of a problem simultaneously

  24. Visual Information Processing • Trichromatic (three-color) Theory • Young and Helmholtz • three different retinal color receptors that are sensitive to specific colors • Red • Green • Blue • Additive color making – addswavelengths andthus increases light

  25. Color-Deficient Vision • People who suffer red-green blindness have trouble perceiving the number within the design • They lack functioning red- or green- sensitive cones, or sometimes both • Examples

  26. Visual Information Processing Opponent-Process Theory- opposing retinal processes enable color vision “ON” “OFF” redgreen greenred blueyellow yellowblue black white white black

  27. Opponent Process- Afterimage Effect

  28. Color Processing • Summary: Color processing occurs in two stages: (1) the retina’s red, green, and blue cones respond in varying degrees to different color stimuli, as the trichromatic theory suggests, (2) then their signals are processed by the nervous system’s opponent-process cells, en route to the visual cortex.

  29. Visual Information Processing • Color Constancy • Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

  30. Audition • Audition • the sense of hearing • Frequency • the number of complete wavelengths that pass a point in a given time • Pitch • a tone’s highness or lowness • depends on frequency • Long waves have low frequency and low pitch • Short waves high frequency and high pitch

  31. The Intensity of Some Common Sounds Decibels are the measuring unit for sound energy

  32. Audition- The Ear • Middle Ear • chamber between eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window • Inner Ear • innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs • Cochlea • coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses

  33. Perceiving Pitch • Place Theory – best explains how we sense high pitches • the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated • Frequency Theory – best explains how we sense low pitches • the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch

  34. How We Locate Sounds

  35. Hearing Loss • Conduction Hearing Loss • hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea • Ex: eardrum punctured • Sensorineural Hearing Loss – more common • hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve • Also called nerve deafness

  36. Amplitude required for perception relative to 20-29 year-old group 1 time 10 times 100 times 1000 times 32 64 128 256 512 1024 2048 4096 8192 16384 Frequency of tone in waves per second Low Pitch High Hearing Loss • Older people tend to hear low frequencies well but suffer hearing loss for high frequencies

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