Vision

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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

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Vision

• Hue
• dimension of color determined by wavelength of
  light
• Wavelength also determines the pitch of sounds

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Vision

• Intensity
• amount of energy in a wave determined by
  amplitude
• brightness
• loudness

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The spectrum of electromagnetic energy
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Differing Eyes

Bee detects reflected ultraviolet wavelengths
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Vision
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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

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Vision

• Accommodation- the process by which the eyes
  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

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Vision

• Acuity- the sharpness of vision (can be affected
  by distortions in the eyes 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

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Vision

• Normal Nearsighted Farsighted
  Vision Vision
  Vision

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Myopia Simulation
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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

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Retinas 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 eyes cones cluster

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Blind Spot
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Retinas 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

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Vision- Receptors
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• Light energy ? Rods and Cones ? Bipolar Cells
• ? Ganglion Cells (axons form the optic nerve)

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Pathways from the Eyes to the Visual Cortex
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Visual Information Processing

• Feature Detectors
• Located in the visual cortex
• nerve cells in the brain that respond to
  specific features
• shape
• angle
• movement

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How the Brain Perceives
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Illusory Contours
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If the region responsible for perceiving
faces were damaged, you would have difficulty
recognizing familiar faces
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Visual Information Processing

• Parallel Processing
• simultaneous processing of several aspects of a
  problem simultaneously

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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

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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

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Visual Information Processing

• Opponent-Process Theory- opposing retinal
  processes enable color vision
• ON OFF
• red green
• green red
• blue yellow
• yellow blue
• black white
• white black

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Opponent Process- Afterimage Effect
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Color Processing

• Summary Color processing occurs in two stages
  (1) the retinas 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
  systems opponent-process cells, en route to the
  visual cortex.

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Visual Information Processing

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

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Audition

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

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

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Perceiving Pitch

• Place Theory best explains how we sense high
  pitches
• the theory that links the pitch we hear with the
  place where the cochleas 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

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How We Locate Sounds
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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 cochleas
  receptor cells or to the auditory nerve
• Also called nerve deafness

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Hearing Loss

• Older people tend to hear low frequencies well
  but suffer hearing loss for high frequencies