chapter 4: the visual cortex and beyond

Question 1

describe the pathway from the retina to the brain

Answer 1

• optic nerve
• optic chiasm
• 90% go to lateral geniculate nucleus (LGN), 10% go to superior colliculus
• cortex

Question 2

what happens at the optic chiasm

Answer 2

anything in the right visual field (regardless of the eye), end up on the left hemisphere of the brain
vice-versa

Question 3

what is the function of the LGN and where is it located

Answer 3

regulates neural info as it flows from retina to cortex
- receives more signals from the cortex than the retina called “feedback”
located in the thalamus

Question 4

what is the function of the superior colliculus

Answer 4

controls eye movement

Question 5

what are the other names for visual receiving area

Answer 5

striate cortex
V1

Question 6

what are simple cortical cells

Answer 6

cells in the striate cortex with side-by-side receptive fields that have excitatory and inhibitory areas

Question 7

Explain how simple cells respond best to certain orientation

Answer 7

• layout of the excitatory and inhibitory areas are parallel to each other
• the more tilted it is, the more it will stimulate the inhibitory area and decrease firing rates

Question 8

what are complex cells

Answer 8

cells that respond best to correctly oriented bar of light that moves across the entire receptive field

Question 9

what are end-stopped cells

Answer 9

cells that fire to moving lines of a specific length or to moving corners or angles

Question 10

what are end-stopped cells

Answer 10

cells that fire to moving lines of a specific length or to moving corners or angles

Question 11

why are simple, complex and end-stopped cells also called feature detectors

Answer 11

because they fire in response to specific features of the stimulus, such as orientation or direction of movement

Question 12

define selective adaptation

Answer 12

firing causes neurons to eventually become fatigued or forces them to adapt

Question 13

what are the two physiological effects caused by selective adaptation

Answer 13

1. neuron’s firing rate decreases
2. neuron fires less when that stimulus is immediately presented again

Question 14

define what is the contrast threshold that was used to measure the effect of selective adaptation to orientation

Answer 14

minimum intensity difference between two adjacent light and dark bar until they can barely be seen

Question 15

define selective rearing

Answer 15

if an animal is reared in an environment that contains only certain types of stimuli, then neurons that respond to these stimuli will become more prevalent

Question 16

explain why results of selective rearing experiments are described as “use it or lose it”

Answer 16

presenting the rearing orientation over a period of days/weeks keeps the neurons that respond to that orientation active.
- other neurons lose their ability to respond to their orientations

Question 17

explain the experiment done by Blakemore and Cooper on the kittens

Answer 17

• kittens kept in the dark from birth to 2 weeks
• then placed in striped tube for 5 hours a day
  kittens seemed blind to orientation that they hadn’t seen in the tube

Question 18

what is the retinotopic map

Answer 18

electronic map of the retina on the cortex

Question 19

define the cortical magnification and cortical magnification factor

Answer 19

apportioning of a large area on the cortex to the small fovea
- cortical magnification factor: size of magnification

Question 20

true or false? the more space on the cortex allocated for an image translates into a larger size of the image

Answer 20

false, it translates into a better detailed vision

Question 21

explain what location columns and orientation columns are

Answer 21

organization of the cortex where all neurons in a perpendicular column to the surface of the cortex represent the same location on the retina and the same orientation

Question 22

define a hypercolumn

Answer 22

a location column with all of its orientation columns

Question 23

explain the tiling effect

Answer 23

a scene is divided into small areas. each area sends info to one location column. together, they cover the entire visual field

Question 24

true or false? each visual area can overlap each other

Answer 24

true

Question 25

explain how visual signals are processed as they move from V1 to higher-level extrastriate areas

Answer 25

receptive field sizes gradually increase.
as we move up this hierarchy of extrastriate cortex, visual scene builds up from line or edge to entire shapes and objects

Question 26

define the technique called ablation

Answer 26

destruction or removal of tissue in the NS

Question 27

describe the object/landmark discrimination problem and the ablation part of the experiment

Answer 27

object: be able to discriminate between two objects and put aside “target object”
landmark: be able to remove cover of food closest to “landmark”
ablation: temporal or parietal lobes removed
conclusion: what and where pathway

Question 28

what does the term dorsal and ventral refers to

Answer 28

dorsal: back or upper surface of an organism
ventral: lower part of the brain

Question 29

true or false? specific ganglion cells exists for both dorsal and ventral stream

Answer 29

true

Question 30

define neuropsychology

Answer 30

study of the behavioral effects of brain damage in humans

Question 31

what is the double dissection method

Answer 31

damage to one area of the brain causes function A to be absent while function B is present in one patient
damage to another area of the brain causes function B to be absent while function A is present in another patient

Question 32

why can the dorsal pathway also be called the how pathway

Answer 32

because it determines how a person carries out an action.

Question 33

explain the experiment that supports the idea that perception and action are served by different mechanisms

Answer 33

illusion: line 1 is longer, line 2 appears longer
- task 1: length estimation task
- task 2: grasping task
illusion works for perception not for action

Question 34

describe the neurons found in the inferotemporal cortex

Answer 34

increase in receptive fields continues through the what stream
- largest receptive fields at the apex of the stream in IT cortex respond to more complex objects

Question 35

name a few structures in the medial temporal lobe (MTL)

Answer 35

parahippocampal cortex
entorhinal cortex
hippocampus

Question 36

the MTL structures are extremely important for __

Answer 36

memory

Question 37

define the contextual modulation effect

Answer 37

effect of stimulating outside the receptive field can affect what’s happening within the receptive field

Question 38

describe gross’s experiments on neurons in the IT cortex of the monkey

Answer 38

presented stimuli like lines, squares, circles, etc
- one neuron refused to respond to anything, until experimenter pointed at something in the room
- expanded types of stimuli presented
- found neurons that responded to real-life, complex objects like hands and faces

Question 39

what is the link between MTL neurons and hippocampal neurons

Answer 39

neurons in the MTL that respond to perceiving specific objects or events are also involved in remembering these objects and event

Question 40

what is perceptual organization

Answer 40

lines of the same orientation are perceived as a group that stands out from the surrounding clutter