chapter 5- vision

Question 1

what is the law of specific nerve energies?

Answer 1

-the brain encodes information based on which neurons are active. its not based on the stimuli themselves but instead these neurons. if you touch your eyes you see things, if you stillmulated audio receptors you would hear

Question 2

what is the centre of the iris

Answer 2

pupil

Question 3

light enters centre of iris. the ____ . it is focused by ______ (adjustable) and ____ (not adjustable, and projected to the _____, the rear surface of the eye

Answer 3

pupil, … lens, cornea…retina

Question 4

the visual system does not replicate images instead it

Answer 4

codes it by various neuronal activity

Question 5

describe travel of light through the receptors

Answer 5

it first goes to receptors at the back of the eye, then to bipolar cells then to ganglion cells. the ganglion axons go to the back of the brain to the optic nerve. there are also amacrine cells which get information from bipolar cells and send it to other bipolar cells, amnicrane cells and ganglion cells

Question 6

what do amnicrine cells do

Answer 6

refine the input to ganglion cells enabling certain ones to respond mainly to particular shapes, directions of movement, changes in lighting color and other visual features

Question 7

what creates the blind spot

Answer 7

the axon join the optic nerve and it has no receptors

Question 8

why don’t you notice blind spot

Answer 8

brain fills in the gap, anything in blind spot one eye is visible to the other eye

Question 9

the fovea is the

Answer 9

central portion of the retina, tiny and specialized for acute specialized vision..it is so detailed because almost no blood vessels or ganglion axons

Question 10

the more important part of seeing detail from the fovea is

Answer 10

each receptor connects to a single bipolar cell which connects to a single ganglion cell that has an axon to the brain

Question 11

the ganglion cells in the fovea of humans are called

Answer 11

midget ganglion cells

Question 12

why are they called midget ganglion cells

Answer 12

each is small and responds to a single cone , so each cone in the fovea has a direct route to the brain

Question 13

vision is dominated by what you see in fovea because

Answer 13

midget ganglion cells provide 70 percent of the input to the brain

Question 14

“eyes like a hawk” is a phrase because

Answer 14

birds have two fovea one looking ahead and one straight and their eyes are bigger

Question 15

where do predatory birds have most receptors and why

Answer 15

top half because they spend most time looking down. input from bottom goes to top of the fovea

Question 16

why can the brain not detect the exact location or shape of a peripheral light source? what advantage does it have instead

Answer 16

because towards to periphery more and more receptors converge onto bipolar and ganglion cells ..has sensitivity for dim light, perception of fainter things

Question 17

in the peripehrary the ability to detect detail is limited by

Answer 17

inference by nearby objects

Question 18

rods are in the ____ and for ___ light and cones are in the ___ and for ____

Answer 18

peripherally, dim…..fovea, color

Question 19

are there more rods or cones ? what’s the ratio?

Answer 19

more rods..20:1

Question 20

visible lights consists of electromagnetic radiation within the range

Answer 20

less than 400nm to more than 700nm

Question 21

why do we call the wavelengths light

Answer 21

the receptors in our eyes are tuned to detecting them

Question 22

what does trichromatic theory/young helmholts theory say about how we see color

Answer 22

we perceive color through the relative rates of response by three kinds of cones, each one maximally sensitive to a different set of wavelengths

Question 23

how did hemholtz decide on three?

Answer 23

people could match any color by mixing appropriate amounts of just three wavelengths?

Question 24

what happens when all 3 types of wavelengths are active

Answer 24

we see white or gray

Question 25

which wave length cones are more abundant? because of this we its harder to see what dots

Answer 25

medium and long. blue

Question 26

what is the difference in distribution of short medium and long wavelength cones

Answer 26

short is evenly while the other two are distributed haphazardly with differences among individuals .causes small differences. cones are so scarce in periphery no color vision there .

Question 27

what is color constancy?

Answer 27

ability to recognize colours despite changes in lighting

Question 28

why should we avoid talking about the color of a wave length of light?

Answer 28

a certain wavelength of light can appear as different colours depending on the background

Question 29

explain retinx theory

Answer 29

combo of the words retina and cortex. the cortex is comparing information from different parts of the retina to determine the brightness and color for each area...

Question 30

what was dale purves idea that was more general of the retinix theory

Answer 30

whenever we see something we make an inference...visual perception requires reasoning and inference not just retinal stimulation

Question 31

explain opponent process theory

Answer 31

color vision works in pairs....red,green..yellow blue..white black....when you stare at a color it gets fatigurd...this is because cells in the retina for example one gets excited by short and inhibited by medium/ long...but if you stare at blue for two long that cell becomes fatigued and stops firing as much. you get a decreased response leading you to perceive yellow

Question 32

why can opponent process theory not be the whole story

Answer 32

after images depend on the whole context, not just the light on individual receptors..the cerebral cortex must be responsible not the bipolar or ganglion cells

Question 33

where does the dorsal stream go through

Answer 33

parietal cortex

Question 34

what pathway is the dorsal stream

Answer 34

action, "how" because of importance for visually guided movements

Question 35

what happened to the patient who had damage to her ventral pathway

Answer 35

she couldn't see objects but she could put an envelop through slot but she could not say wether it was horizontal or vertical

Question 36

what happens to patients with dorsal damge

Answer 36

they can identify objects they see while walking but not good at integrating vision with arm and leg movements so they bump into things

Question 37

where is secondary visual cortex

Answer 37

just anterior to v1 in the occipital cortex

Question 38

what is the difference between receptive feilds in v1 and v2

Answer 38

v2 receptive fields are elongated

Question 39

cells of what area respond to corners, textures or complex shapes?

Answer 39

v2

Question 40

which areas are highly sensitive to color and other the disparity between what the left and right eye sees

Answer 40

v2 and v3

Question 41

true or false: both area v1 and v2 respond to lines, edges or sine wave gratings

Answer 41

true

Question 42

cells in the _____ learn to recognize meaningful objects

Answer 42

inferior temporal cortex

Question 43

monkeys responded about the same to mirrored images but not to _____..why?

Answer 43

figure- ground reversal..they and humans perceive it as a white object with black background

Question 44

what happens after a bit of experience viewing an object vs at first?

Answer 44

at first the cell responds mainly to the angle it saw but after experience it responds almost equally to it at different angles regardless of major changes in the pattern that reaches the retina

Question 45

what is a possible bases of object permanence?

Answer 45

monkeys saw an object then new or surprising one appeared. some cells in inferotemprol cortex when an original object objeread and other cells responded strongly to a new object

Question 46

what is visual agnosia? explain how it presents

Answer 46

an inability to recognize objects despite otherwise satisfactory vision....damage to temporal lobe...can describe objects but fail to recognizenzie what they are

Question 47

true or false: most brain objects activate one brain area more than another in a specialized fashion

Answer 47

false

Question 48

what are the three objects that produces specific responses and what are the locations

Answer 48

- pictures of places: parahippocampal cortex - faces: fusiform gyrus in inferior temporal cortex especially in right side - bodies: an area close to the face area

Question 49

how far one sees is dependant on what

Answer 49

how far light travels before it strikes ones eyes

Question 50

explain sensation vs perception

Answer 50

sensation is registration by the sensory organ (eyes) of a physical stimuli and perception is how we interpret what we see

Question 51

describe the cornea

Answer 51

clear outer covering, protects the eye, damage leads to eye pain and blurry vision

Question 52

what is the iris

Answer 52

colored area, opens and closes to allow less or light through the pupil

Question 53

the _______ is at the back of the eye, is the most important and has photo receptors

Answer 53

retina

Question 54

what are the two common refractive errors? describe them

Answer 54

usually, normal vision focuses directly on retina.... there is myopia (near sightedness : near to you is clear) where focal point light focuses in front of/ before the retina. the eyeball is elongated or curved on cornea hyperopia: farsightedness: focal point falls behind the retina lens can be too flat

Question 55

what is ther energy released by rods and cones when struck by light

Answer 55

proteins called oxins

Question 56

the perception of color depends on _____

Answer 56

wavelength of light

Question 57

what do night vision goggles use

Answer 57

infrared

Question 58

which color cones we have the least of

Answer 58

blue

Question 59

according to trichromatic theory what determines color

Answer 59

the ratio of activity across the three cones

Question 60

according to opponent process theory the brain perceives color on a continuum from ____ to____ and another ______ to _____

Answer 60

red to green, yellow to blue

Question 61

how does the inability to distinguosh between red and green occur

Answer 61

long and medium wavelength cones having the same photopigment

Question 62

which cells make inhibitory contact onto bipolar cells

Answer 62

horitzontal cells

Question 63

what happens when youre startled

Answer 63

information goes to the superior colliculis so that it can get there fast and not need higher response

Question 64

axons from the ____ (____) half of each retina cross over to the oppisite side of the brain. axons from the ______ (____) half of each retina remain on the same side of the brain

Answer 64

nasal (inside)....... temporal (outer)

Question 65

describe the optic chiasm

Answer 65

the junction of the 2 optic nerves from each eye

Question 66

most axons go to the ____

Answer 66

lateral geniculate nucleus of the thalamus

Question 67

what are receptive fields

Answer 67

part of the visual field that either excite or inhibits a cell in the visual system of the brain

Question 68

what kind of receptive field do ganglion cells have

Answer 68

centre-surround

Question 69

what are the three categories of genglion cells

Answer 69

parvocellular, magnocellular, koniocellular

Question 70

describe parvocellular cells

Answer 70

theyre in the fovea, small cell body, color

Question 71

describe magnocellular cells

Answer 71

large cell body, light and movement

Question 72

what is the inability to recognize faces called

Answer 72

prosopagnosia

Question 73

what about infants suggsest built in recogotion of faces

Answer 73

they look at them more than anything else

Question 74

the "________ responds to a stimulis moving in a particular direction

Answer 74

middle temporal cortex (mt/v5)

Question 75

the _______ respons to expansion, contraction or rotation of a visual stimulis

Answer 75

medial superior temporral cortex