Chapter FIve

Question 1

VIsion

Answer 1

• Physical stimulus: light particles and waves; electromagnetic radiation
• Eyes transduce electromagnetic radiation (light)
• Small range that can be detected
• Birds and insects can see shorter wavelengths of light
• Snakes can detect infrared
• Wavelengths of light bounce off of objects and the reflective light hits our eye

Question 2

Cornea

Answer 2

• clear outside of the eye that light oases through;

- bends and focuses light

Question 3

Pupil

Answer 3

• black spot in the center of the eye;

- the hole at the center of the iris

Question 4

Iris

Answer 4

• aperture that expands or opens of the pupil depending on the eye;
• colored part

Question 5

Lens

Answer 5

• hidden behind the pupil;
• functions the way a camera lens functions;
• allows us to focus on things (fingers) changes shape;
• soft and flexible;
• muscles attached to it pull or relax

Question 6

Retina

Answer 6

• Where transduction occurs

- 3 layers

Question 7

Retina Layers

Answer 7

• Top layer: Ganglion cells; take information to the brain; combine the activity of cones and rods; receptive field for ganglion cells that corresponds with an area of the visual field
• Middle layer
• Bottom layer: Receptor cells
• The light has to pass through other layers to get to the photoreceptors
• Not all the light is making it to the photoreceptors

Question 8

Photopigments

Answer 8

• Light sensitive
• Light hits them and causes chemical reactions and that changes the amount of neuro transmitter being releases
• Cones
  
  • Uses more light
  • Distinguish color
  • Depending on the photopigment different wavelengths of light are going to activate different photoreceptors
• Rods
  
  • Don’t require as much light
  • Cant discriminate between different colors
• Photoreceptors are not evenly dispersed throughout the retina
• Blind spot = where the axons leave the eye and have no photoreceptors

Question 9

Fovea

Answer 9

• Cones are almost exclusively located in the fovea
• Densely packed in the fovea than in other parts of the eye
• This is where the light from objects we are directly looking at are projected
• Rods are on the other part and get light from the background and not as densely packed

Question 10

How to we detect color

Answer 10

• Activate pigments in blue, red, and green cones
• Trichromats
• Primary colors make up the other colors
• detect other colors by seeing how much they activate the three cones
• i.e. yellow activates blue and green
• Red green color blindness
• Mantis shrimp
  
  • 12 different types of cones
  • The most we know of different animals
  • Cant tell the difference between colors we know
  • Underwater filters out long wavelengths and see mostly blue
  • Polarized light

Question 11

On-center Off-surround cells

Answer 11

• Center of the receptive field
  
  • If the light is in the center of the receptive field the ganglion fires
• Surround of the receptive field
  
  • If the light doesn’t cross the center of the receptive field, the ganglion cell is inhibited
• If light falls partially on the center and partially on the surround it leads to no change
• on-center off-surround ganglion cells and LGN cells
• Lateral inhibition
• Helps us detect the edge of things
• Where an object ends and where it begins
• Allows the brain to get very specific information about where the edge is, where light meets dark

Question 12

VIsion and the thalamus

Answer 12

• Lateral geniculate nucleus
• On-center off-surround cells
• From the LGN the information goes to the primary visual cortex in the occipital lobe
• Consequence is both hemispheres receive information from both eyes
• Cells are organized based on which eye the information is coming from

Question 13

ocular dominance columns

Answer 13

• Its organized so that one area is only responding to information from the left eye
• Keeps the different eyes distinct because both hemispheres receive input from all of them
• Having two overlapping means that each eye gets a different view of an object
• Helps with depth perception

Question 14

What happens when you limit the input of one eye to the visual cortex?

Answer 14

• The eye that gets covered up gets very little amounts of cortex that continue to process information from it
• More of the cortex is attributed to the good eye
• If the eye is uncovered, the monkey wont see very well out of the eye because not as much of the brain is processing information from it
• When young children have a good eye and a weak eye doctors cover the good eye so that the weak eye can catch up
• Auditory processing in blind people; occipital lobe lights up

Question 15

SImple cells in V1

Answer 15

• The firing processing of these neurons are different than the ganglion cells and LGN
• Putting the light in the receptive field and of the correct orientation cause them to fire
• This cell likes vertical rather than horizontal
• Horizontal will not cause it to fire
• These cells are responding to more complicated stimuli in more complicated ways

Question 16

Orientation Columns

Answer 16

• The preferred orientation changes in a continuous fashion

- Both the orientation columns and ocular dominance columns

Question 17

Retinotopic organization and BLobs

Answer 17

• Retinotopic organization
• Receptive fields right on the fovea are in the center and those farther away are in the periphery different areas will fire
• Blobs
• These neurons are also selective for certain colors
  
  • Input starts in the cones
• Intrablob regions do not distinguish between colors
  
  • Input starts in the rods

Question 18

Serial and Parallel Processing

Answer 18

• Serial process, goes in a specific order
  
  • Can’t always work because it would take too long
• Parallel processing is when you split up the tasks
• Information from the occipital cortex goes to the parietal cortex and inferotemporal cortex
• The stimuli that get the cells to react are getting more and more complicated

Question 19

Section V4

Answer 19

• Color processing, sometimes shape

- When people damage V4 they become atypically colorblind; achromatopsia, absence of color vision

Question 20

MT/V5

Answer 20

• A bar of light that is moving activates them
• Apart of the movement detection of visual processing
• Akinetopsia = damage to this area
  
  • Everything is a series of still moments
  • Pouring tea you cant tell when you get to the top
  • crossing the street with this disorder is very dangerous

Question 21

Superior COlliculi

Answer 21

• Some information goes to the superior colliculus in the midbrain
• Visual reflexes and unconscious responses to visual stimulus
• More primitive visual processing
• Works even when V1 is damaged (cortical blindness)
• People will duck from a baseball but won’t know why known as “blind sight”
• People can walk around furniture

Question 22

Visual cortex lesions vs. subcortical superior colliculi lesions

Answer 22

• Sunflower seed (localization task)
  1. If you lesioned V1 they could follow the seed with their eyes
  2. If you lesioned the S.C. they could not follow the seed with their eyes
• Vertical striped door (discrimination task)
  1. If you lesioned V1 they could not tell to go through the vertical door
  2. If you lesioned the S.C. they could still of through the vertical door