PSY280 - 4. VISION IN THE CORTEX

Question 0

in the light

Answer 0

packets of light hit retinal - isomerization - retinal changes shape to detach to opsin
once rhodopsin is activated - cGMP becomes GMP
no cGMP means sodium channels shut
more K moves out driving potential down -70mV
thus in the light release more neurotransmitter

Question 1

in the dark

Answer 1

CGMP: keep doors open, sodium rushes in cell, K+ channels open, K moves out
trading ions to return them, creating a dark current, -40mV in the dark which is slightly depolarized
it releases a lot of neurotransmitter

Question 2

On + Off Bipolar

Answer 2

On bipolar: in light less neurotransmitter - spontaneously releases more in the absence of light - stimulating ganglion cell to fire more
product of strength of activation - inhibition
inhibition lateral is proportional to excitation
doesn’t reflect diff in illumination - enunciates the shift in contrast

Question 3

On + Off Bipolar

Answer 3

lights are off - photoreceptors releasing a lot of neurotransmitter
off bipolar cells release a lot + excite ganglion cells
now it’s opposite
mirror curve - reversed
these 2 curves do not cancel each other out
at the level of cortex, they see it as a signal that there is a change in light intensity

Question 4

On + Off Bipolar

Answer 4

Lateral connections via horizontal & amacrine cells send information to nearby bipolar & RGCs, changing the firing rate of the RGCs under non- uniform lighting conditions.
in uniform light you activate centre surround cells which cancel each other out
boost contrast signals

Question 5

On + Off Bipolar

Answer 5

horizontal cells connecting lateral cells creating lateral inhibition
centre shine = active ganglion cell
surround = less activation on ganglion cell
whether the bipolar cells are on or off dictate whether its centre surround

Question 6

retinotopic mapping & cortical magnification

Answer 6

Activity on the retina causes activity in the cortex.
There is disproportionately more cortex dedicated processing information from the fovea.
info adjacent on retina is processed in adjacent neurons in the cortex

Question 7

retinotopic mapping & cortical magnification

Answer 7

beside each other in visual field, on the retina, processed by neurons in V1 that are also adjacent
cortical magnification” more cortex processing fovea
necessary for tasks that require high visual acuity - reading, object recognition

Question 8

Vernier acuity & grating judgments

Answer 8

vernier acuity: high acuity, can sense smallest diff
how diff does reference have to be just to notice the diff
grating
both use JNDs to estimate visual acuity in participants.

Question 9

• Spatial organization

Answer 9

way stimuli at specific locations in the environment are represented by activity at specific locations in the nervous system

Question 10

Electronic map of V1

Answer 10

Points on the retinal image cause activity in the cortex
Retinotopic map: electronic map of the retina where locations on the cortex correspond to locations in the retina
Points that are close together on the object and on the right noble activate neurons that are close together in the brain

Question 11

Electronic map of V1

Answer 11

More space being allocated two locations near the fovea then to locations in the peripheral retina
Cortical magnification: apportioning to the small phobia of a large area on the cortex
Extra cortical space allotted to letters and words at which person is looking provides extra neural processing needed to accomplish tasks such as reading

Question 12

Visual angle

Answer 12

amount of space something takes up on the retina
depends on how far away it is
visual angle is absolute measure of how much space is taken up on the retina
mouse + elephant take up same VA
60 minutes of arc to 1 visual angle

Question 13

cortical magnification

Answer 13

estimate of cortical magnification, researchers presented spots of light of varying visual angles & measured the size of the fMRI response.
how much of visual cortex activated by spot of light
1 degree VA + 1mm = 1:1
1 degree VA + 12 mm = 1:12
ratio = M for magnification

Question 14

cortical magnification

Answer 14

higher participant’s visual acuity, the greater their magnitude of cortical magnification
low acuity: 12 minutes of arc necessary
high acuity: small diff in minutes can still reliably detect diff
negative relationship in both tasks

Question 15

columns in V1 (striate cortex)

Answer 15

Neurons perpendicular to the surface of the cortex have RFs at approximately the same location on the retina.
highly systemic organized of preference neurons
receptive field locations on retina are same location
receptive fields are one on top of each other perpendicular of cortex

Question 16

columns in V1 (striate cortex)

Answer 16

neurons perpendicular are interested not only to same location, but also stimuli of same orientation
move just a little bit, preference changes just a little bit

Question 17

Location and orientation columns

Answer 17

Striate cortex is organized into location columns that are perpendicular to the surface of the cortex so that all of the neurons within a location call them have their receptive fields at the same location on the retina
Cortex is organized into orientation columns, each column containing cells that correspond best to a particular orientation

Question 18

One location: many orientation columns

Answer 18

Neurons in that location: receive signals from a particular location on the retina, which correspond to a small area in the visual field
Hyper column: Receives info about all possible orientations that fall within a small area of the retina and therefore well-suited for processing info from a small area in the visual field

Question 19

columns in V1 (striate cortex)

Answer 19

cut across the orientation columns, they found orientation preference changed systematically
systematic variation across orientations along the parallel of the cortex surface

Question 20

Ocular dominance

Answer 20

neurons in striate cortex will respond to stimulation from either eye, but tend to prefer one eye over the other
LGN are eye specific, but in V1, neurons respond to both eyes
however, they tend to have a preference
ocular dominance varies specifically as well

Question 21

Hypercolumns

Answer 21

pair of ocular dominance columns in conjunction with one complete series of orientation columns.
columns of neurons that prefer info from the right eye beside columns that prefer left eye
respond more strongly to preference

Question 22

Hypercolumns

Answer 22

cubes in V1 that are 1/4 mm x 1/2 mm
ice cube tray model
retina organization then will also be the same
columns prefer a certain area of the visual field

Question 23

Tilting

Answer 23

working together these columns cover the entire visual field

Any scene is presented in the striate cortex by amazingly complex pattern of firing

Question 24

Hypercolumns

Answer 24

hypercolumns in cortical region on the fovea have a small receptive field large receptive fields give sensitivity not detail small receptive field means you need more (hypercolumns) cortex which explains cortical magnification midget cells receiving info from fovea cones to details (stationary, colour contrast) all of which importnant for object identification

Question 25

Parallel visual channels

Answer 25

Pathways from LGN to V1 stay segregated compartementalization allows brain to be more efficient due to specialization parallel visual channels form basis for seperation of duties at early stage of visual processing

Question 26

Magnocellular

Answer 26

``` retinotopic emphasis: peripheral receptive field size: large contrast sensitivity: high color sensitivity: low spatial resolution: low temporal resolution: high motion sensitivity: high neural transmission: rapid ```

Question 27

Parvocellular

Answer 27

``` retinotopic emphasis: central receptive field size: large contrast sensitivity: low color sensitivity: high spatial resolution: high temporal resolution: low motion sensitivity: low neural transmission: sluggish ```

Question 28

extrastriate cortex

Answer 28

borders V1 & is also important for visual processing: Broadmann’s Area 18 & 19 broadmann identified regions as distinct

Question 29

association areas

Answer 29

Using electrophysiology, behavior & lesion studies, researchers determined these pathways extend beyond the striate cortex into the association areas. areas of cortex that connect visual info with meaning

Question 30

Monkey Cortex

Answer 30

Magnocelluar - V1 - area MT Parvocellular - V1 - V4 neurons in this MT region prefer object motion + movement detail v4 - object form, colour, textures - variables important for identifying objects V5 in humans instead of MT

Question 31

Dorsal

Answer 31

area MT - parietal lobe | pathway is responsible for determining where in space an object is

Question 32

Ventral

Answer 32

V4 - temporal lobe | pathway responsible for determining the identity of an object.

Question 33

Where pathway

Answer 33

halfway leading from the striate cortex to the parietal lobe | the upper part of the brain, where the parietal lobe is located is the dorsal part of the brain

Question 34

Ventral pathway [what]

Answer 34

lower part of the brain where Temporel lobe is located is ventral part of the brain pathway leading from the striate cortex to the Temporel lobe

Question 35

pathways

Answer 35

highly interactive segregation done in parallel with cortex dorsal - body + eye movements dependent on visual input based on magno function but what object is guides how you should act on it these provide top down processes

Question 36

pathways

Answer 36

Properties of the ventral and dorsal streams are established by two different types of ganglion cells in the retina which transmit signals to different layers of the LGN processed in the what pathway, not where pathway dorsal stream provides info about how to direct action with regard to stimulus Neurons in the parietal cortex that respond when a monkey look set an object and when it reaches toward the object

Question 37

Ablation

Answer 37

remove it and see how the system now functions. | refers to distraction or removal of tissue in the nervous system

Question 38

Landmark description problem

Answer 38

goal in this task is to remove food well cover that is closest to the cylinder. parietal lobe removed had difficulty solving the landmark discrimination problem

Question 39

Object discrimination problem

Answer 39

shown one object and was been presented with two choice task which included the target and another stimulus part of the Temporel lobe, object discrimination problem was very difficult

Question 40

Neuropsychology

Answer 40

researchers look for dissociations in functional deficits. naturally occurring lesions understand cognitive function of those areas pairs of patients with opposing deficits in function study of behavioral effects of brain damage in humans

Question 41

Feedback

Answer 41

backward flow of info provides information from higher centers that can influence the signals blowing into the system

Question 42

double dissociations

Answer 42

Involve two people: in one person, damage to one area of the brain causes function A to be absent while function B is present, and the other person damage to B causes function B to be absent function a is present orientation distinguishes the identity of these 2 shapes processed in the what pathway, not where pathway

Question 43

D.F

Answer 43

DF couldn’t match the orientation* of the card to the slot. D.F Carbon monoxide poisoning - damage to temporal lobe D.F has difficulty finding orientation of slot Dorsal pathway should be how pathway or the action pathway because it determines how a person carries out an option

Question 44

D.F

Answer 44

she can’t match the orientation, but she can push the card in the slot action pathway was preserved, but her perception pathway was compromised. dorsal stream is for taking action provide info on how to interact with object interaction betw what object is + how to interact with it

Question 45

Modularity: structures for faces, places and bodies

Answer 45

structure specialized to process info about a particular type of stimulus Specific areas in the Temporel lobe respond best to particular types of stimuli

Question 46

Behavior of people without brain damage

Answer 46

Length estimation task: indicate how perceive the lines length by spreading their thumb and index finger Involves the ventral what stream Grasping task: reach toward the lines and grasp each line bites and Involves the dorsal how stream Perception + action are served by different mechanisms In the length estimation task, subjects judged 1 was looking shorter than line 2 but in the grasping task they separated their fingers farther apart

Question 47

action stream deficits

Answer 47

perceptual streams are preserved. | difficulty acting on object because action stream is damaged

Question 48

Face neurons in the Monkeys IT cortex

Answer 48

Inferotemporal cortex many neurons that respond it best to faces The areas in the monkey Temporel lobe that are particularly rich in these neurons

Question 49

rod & frame illusion

Answer 49

is it just the action/perception stream fooled Using the same stimuli, researchers had participants do a action task & a perceptual task. grasping - change the rod position to match stimuli matching task - say left or right to match we assume visual illusions occur in what pathway

Question 50

rod & frame illusion

Answer 50

The results of this experiment were consistent with Milner & Goodale, but recent evidence suggests there is still room for Ungerleider & Mishkin. illusion is huge in matching task magnitude of grasping task illusion is smal action pathway seperate from basic perception? diff parts of parietal in knowing where things are in space to act + just plain knowing where it is

Question 51

inferior temporal cortex

Answer 51

visual areas in temporal lobe posterior IT - early complex representations with specific configurations central IT + anterior IT}late complex representation back half close to occipital: combos of line + basic shape central + anterior IT - more toward front - more complicated, doesn’t matter if its upside down

Question 52

anterior IT

Answer 52

Neurons in the anterior IT cortex in monkeys show a preference for faces. neurons in this area that prefer face

Question 53

fusiform face area.

Answer 53

Broadmann’s area 37 corresponds to human analog betw parahippocampal + entorhinal - respond to various representations of ppl neurons in middle area activate when they recognize her, but also to recall who she is

Question 54

• Fusiform face area

Answer 54

located in the fusiform gyrus’s on the underside of the brain directly below the inferotemporel cortex

Question 55

• Parahippocampal place area

Answer 55

activated by pictures depicting indoor and outdoor scenes Important for spatial layout because increased activation occurs both the empty rooms into rooms that are completely furnished

Question 56

Extrastriate body area

Answer 56

activated by pictures of bodies and parts of bodies | The stimuli also activate other areas of the brain as well

Question 57

Fusiform face area

Answer 57

Object such as faces may cause a large focus of activity in the FFA but also cause additional activity that is distributed over wide area of the cortex Visual system is organized functionally with different streams for what and where/how it with specific cortical areas that are rich in neurons that respond to specific types of stimulus such as faces, places and bodies

Question 58

Fusiform face area

Answer 58

betw parahippocampal + entorhinal - respond to various representations of ppl neurons in middle area activate when they recognize her, but also to recall who she is Broadmann’s area 37 corresponds to the human analog

Question 59

Modules

Answer 59

While there is some specialization through modules, categorical stimuli still activate other areas of the brain. areas of specialization can be misleading various stimuli produce activation in various parts of the brain lots of overlap activation for face, house, chairs there is distribution of representation

Question 60

Face recognition

Answer 60

holistic process we don’t recognize indiv elements of person + assembleing them later it needs to be in a particular configuration relationship of features configuration: distance betw eyes, + their distance to middle of mouth similar configuration adds to their similarity

Question 61

FFA

Answer 61

processing holistic + expertly info, we are just all face recognition experts Novices tend to focus on one aspect of a stimulus for discrimination. Experts tend to focus on the whole stimulus for discrimination

Question 62

Greebles

Answer 62

features vary in a familiar way; holistic processing is required to discriminate individuals. forcing ppl to rely on holistic processing trained ppl to be greeble experts got really good at distinguishing them

Question 63

Greebles

Answer 63

FFA responded to greebles once participants became experts | after training nearly identical response rates to both greebles + faces

Question 64

3 bifurcations

Answer 64

3 splits in processing retina - Sc, most to LGN LGN - MAGNO + PARVO - V1 V1 - dorsal, ventral