Sensation and Perception

1
Sensation and Perception

• Vision Hearing

2
The Visual System

• Light enters through the cornea which is the
  protective coating over the front of the eye
• Light passes through the pupil, the opening in
  the center of the iris, the colored part of the
  eye that contracts over the pupil

3
The Visual System

• Light moves through the lens, which focuses the
  image based on distance (close round, far
  flat)
• Lens focuses image on the retina, the inner
  lining of the eyeball
• The center of your visual field is the fovea,
  which is the small indent behind the lens

4
Receptor Cells

• Retina contains receptor cells
• Rods are responsible for intensities of light and
  dark
• Night vision
• 120 millions per retina
• Located around the fovea and fade to the furthest
  edges of the retina
• Several rods connect to specialized neuron
  (bipolar cells)
• Cones are responsible for color
• 8 million per retina
• Located mainly in the fovea
• One specialized neuron (bipolar cell) per cone
• In dim light, cones are not stimulated so you see
  more in white, black, and gray

5
Visual Acuity

• The ability to visually distinguish fine details
• The words in the sentence X are clearest in the
  middle.
• Notice that you can see only about 4 letters to
  each side in the clearest vision.
• Outside the fovea, visual acuity drops by 50

6
Adaptation

• Visual adaptation changes based on the amount of
  light available
• Dark adaptation occurs when the rods and cones
  become more sensitive to light
• Causes issues when driving at night
• 30 minutes
• Light adaptation occurs when rods and cones
  become less sensitive to light
• 1 minute

7
Brain Connection

• Bipolar cells (neurons) connected to rods and
  cones link up to ganglion cells, which are
  neurons connected to bipolar cells and the optic
  nerve
• 1 million per eye
• The optic nerve carries messages from each eye to
  the brain
• Blindspot is a place on the retina where the
  axons of ganglion cells join the optic nerve (no
  receptor cells located here)

8
Optic Nerves

• Each optic nerve splits into two
• Right side of each optic nerve goes to the right
  side of the brain and vice versa
• The right side of the eye (and thus the brain)
  receive information from the left visual field
• See page 94
• Messages are recorded in the occipital lobe

9
Features

• Brain registers and interprets special elements
• Feature detectors
• Horizontal or vertical lines
• Movement
• Depth
• Color
• Piece information into a meaningful image

10
Eye Movements

• Our eyes are always moving, quivering to make
  sure the retinal image continually changes.
• Stopping sensory receptors would be fatigued
  and images would vanish

11
Blindsight

• Blind due to a stroke or brain damage, not eye
  damage
• When a blind person is asked to point to an
  object placed in front of them (seeming
  impossible), they do it!
• WHY?
• Vision remains intact only neural areas that
  bring vision into awareness are impaired (in
  visual cortex of brain)

12
About color blindness

• 10 of all males show color weakness
• Less than .1 of females do
• Color defects are genetically transmitted

13
Journal 1 (Unit 3)

• Describe your experience if your sensory organs
  were suddenly to become much more sensitive than
  they are normally.

14
Hearing
15
Details

• Frequency length of sound wave
• Longer waves, lower frequency low pitch
• Example tuba
• Shorter waves, higher frequency high pitch
• Example piccolo
• Decibels measuring unit
• 20 whisper
• 60 normal conversation
• Over 85 can produce hearing loss

16
Loudness

• Soft tones activate fewer hair cells
• Louder tones activate more hair cells
• Loudness is determined by the NUMBER of activated
  hair cells
• Only 16,000 cells and are not replaceable! Can be
  damaged by loud tones!

17
How it works

• Sounds waves through auditory canal to eardrum
• Tight membrane that vibrates the waves
• Middle ear transmits eardrums vibrations through
  a piston
• Hammer, anvil, stirrup
• Into inner ear or cochlea
• Filled with fluid that vibrates
• Motion causes ripples in basilar membrane that is
  lined with hair cells
• Movement triggers impulses in connecting nerve
  fibers
• Neural message sent to auditory cortex in
  temporal lobe

18
Detecting Sound

• One ear receives sound a little faster than the
  other
• Sound travels 750 mph difference of .000027
  second! But our ears pick that up!

19
Bone Conducted Sound

• Why does your voice sound so different when
  recorded?
• 2 ways you can hear
• Sound conducted by air waves (what others hear)
• Sound conducted by bone (what it sounds like when
  you munch on popcorn)
• On a recording, sound is strictly made by air
  waves, so its thinner
• Inner or middle ear deafness (not auditory nerve
  damage) can hear through bone conducted sound
• Beethoven