task 3

Question 1

sine wave grating

Answer 1

grating with a sinusoidal luminance profile
->visual system “samples’ the grating discreetly through array of receptors at the back of the retina

Question 2

cones in fovea

Answer 2

“center to center” separation of about 0.5 minute of arc fits acuity limit of 1 minute arc ! we need 2 cones per cycle to able to perceive the granting accurately

Question 3

horizontal & vertical asymmetry

Answer 3

visual acuity falls more rapidly along the vertical midline of the visual field than along the horizontal midline
-> if you fix your eyes on one point better acuity 5 degrees left or right than you do 5 degrees up or down

Question 4

vertical meridian asymmetry

Answer 4

better acuity a foxed distance below the midline of the visual field that above

Question 5

central vision

Answer 5

central vision is slower than peripheral vision (30 vs 60 milliseconds)
foveal cones fave longer axons-> which transmit slow signals better than fast ones
-> the slow response allow foveal cones to increase their reliability by integrating their inputs over a longer time

Question 6

amblyopia

Answer 6

reduced spatial vision, developmental disorder

Question 7

constrast sensitivity function

Answer 7

factors that influence CSF:
* adaptation level of the eye
* temporal modulation of the targets
* age
* refractive state of the individual

Question 8

low frequency yields weak response

Answer 8

spatial frequency of grating too low-> Ganglion cell responds weakly ->part of fat, bright bar of gating lands on the inhibitory surround damping cell’s response

Question 9

high frequency yields weak response

Answer 9

spatial frequency-> too high
->ganglion cell responds weakly-> both bright and dark stripes fall within the receptive field center, washing out response.

Question 10

medium frequency yield strong response

Answer 10

spatial frequency ->just right
->bright bar filling the center
-> dark bar filling the surround

Question 11

lateral geniculate nucleus

Answer 11

relay station on the way from the retina to the cortex

Question 12

magnocellular layers

Answer 12

bottom 2 - magno- large

Question 13

parvocellular layers

Answer 13

top 4- Parvo small

Question 14

if chemical lesions M.l and P.l

Answer 14

M.L- large, fast moving objects
P.L- processing details of stationery targets

Question 15

LGN layers

Answer 15

*each layer receives input from one or the other eye
layers 1, 4, 6 of the right LGN receives input from the left contralateral eye
*2, 3, 5 get their input from the right ipsilateral eye -same side

Question 16

LGN receptive fields

Answer 16

they respond well to stripes and gratings
LGN is not merely a stop on the line from the retina to the cortex

Question 17

why will loud noises would cause us to wake up

Answer 17

there are more feedback connection from the visual cortex to the LGN than feedforward connections from the LGN to the cortex. Thalamus inhibition is not complete.

Question 18

receptive field of striate cortex

Answer 18

because receptive field work a bit different than receptive field of the retina and LGN and they are more enlonged , they respond more rapidly to bars, lines, edges, and gratings than to round spots of light

Question 19

orientation selectively

Answer 19

responds best when the line or edge is just at the right orientation

Question 20

orientation tunning

Answer 20

selective responsiveness-> the cell is tuned to detect lines in a specific orientation

neurons fire when the line is orientated vertically

diminishes at about 30° in either direction

Question 21

orientation tuning curve

Answer 21

a graphical representation of the relationship between line orientation and firing of the neuron. The figure shows the orientation tuning curve if a cell that fires more in response to a vertical line.

There are neurons that respond to all the orientations that exists in the environment.

Question 22

other cells in the striate cortex

Answer 22

selective for horizontal lines and lines at 45, 20, 62

more cells are responsive to horizontal, vertical orientation that to obliques

Question 23

visual acuity in humans and sensitivity to what

Answer 23

humans have somewhat lower visual acuity and contrast sensitivty for oblique targets than for horizontal & vertical targets

Question 24

arrangement is crucial

Answer 24

concentric LGN cells that feed into cortical cells are all in a row

neural interaction (lateral inhibition) within the cortex also plays an important role in the dynamics of orientation of tunning

Question 25

simple cells

Answer 25

* Receptive field: elongated, sensitive to orientation of visual stimuli such as edges and bars * Characteristics: respond to specific orientation, edges, bars. Distinct regions of excitation and inhibition: "on" and " off" regions * Function: involved in the initial processing of visual information detecting edges, contours with specific orientations orientation selectivity respond to small spots of light or stationary stimuli

Question 26

complex cells

Answer 26

* Receptive field: larger compared to simple, less sensitive to exact location, direction left or right * Characteristics: dont have distinct "on" and " off" regions, instead respond to orientated stimuli regardless of their precise location * Function: motion direction and pattern recognition more responsive to overall pattern of activity in R. F * respond only when a correctly orientated bar of light moves across the entire R. F. * particular direction of movement *respond to any lines in any place of R. F

Question 27

end-stopping cells

Answer 27

* Receptive field: similar to complex cells + additional properties related to stimulus length * Characteristics: respond best to oriented stimuli that end within specific regions of their R. F * preference for stimuli of a particular length are extent * Function: detection of line endings and corners in visual stimuli *object perception boundaries and complex shapes * respond to moving lines pf specific length or moving corner or angles

Question 28

cytochrome oxidase

Answer 28

regular array of "CO" bolbs- have been implicated in processing color, perception, processing motion and spatial structure

Question 29

interocular transfer

Answer 29

contrast sensitivity transfer from one eye to the other. this transfer of adaption from the adapted to the non adapted eye is called interocular transfer

Question 30

tilt after effect

Answer 30

strongly supports the idea that human visual system contains individual neurons selective for different orientations

Question 31

strabismus

Answer 31

one eye is turned so that it is receiving a view of the world from an abnormal angle

Question 32

anisometropia

Answer 32

two eyes have different refractive errors (one eye is farsighted and one not)

Question 33

development of low spatial frequency

Answer 33

sensitivity to low spatial frequency develops more rapidly than to high spatial frequencies ( 9 weeks)

Question 34

cortical magnification

Answer 34

spatial representation of the visual scene on the cortex is distorted, with more space being allocated to locations near the fovea than to location in the peripheral retina. The fovea takes 0.01% of the retina's area, but signals from the fovea take up to 8-10% of the retinotopic map on the cortex.

Question 35

cortical magnification

Answer 35

spatial representation of the visual scene on the cortex is distorted because the fovea/central vision is overrepresented.

Question 36

visual cortex and processing info from the fovea

Answer 36

visual cortex dedicates significant amount of neural resources to processing information from the fovea, even though it occupies a very small area on the retina.

Question 37

eccentricity

Answer 37

distance from the fovea (in degrees)

Question 38

feature detectors

Answer 38

simple, complex and end- stopped cells are called feature detectors, because they fire in response to specific features of a stimulus (e.g. orientation, direction of movement, etc).

Question 39

location columns

Answer 39

the striate cortex is organized into location columns, which are perpendicular to the cortical surface. all neurons within a location column have their receptive field at ~ the same location in the retina.

Question 40

orientation columns

Answer 40

The striate cortex is also organized into orientation columns. All neurons within an orientation column respond best to ~ the same orientation.

Question 41

adjacent columns

Answer 41

adjacent slums have cells with slightly different preferred orientations (a column of cells respond best to 90 degree is right next to the column of cells that correspond to 85 degrees)

Question 42

ocular dominance

Answer 42

In the LGN, each cell responds to one eye or the other. In v1, many cells are influenced by input from both eyes. V1 neurons have a preference for stimuli presented in one eye rather than the other eye. the striate cortex is also organized into ovular dominance columns, perpendicular to the cortical surface.

Question 43

1mm

Answer 43

1mm in the cortex contains orientation columns that represent the entire range of orientations. 1-mm dimensions is the size of one location column

Question 44

hypercolumn

Answer 44

A location column with all of its orientation columns. There are 2 ocular dominance columns within each hyper column, one for the left eye and one for the right

Question 45

Double dissociation

Answer 45

2 functions can be disrupted and operate independently of one another empirical evidence D.F patient- damage to ventral pathway: she performed poorly in a static orientation-matching task but did well as soon as she had to perform an action.

Question 46

R.V patient

Answer 46

had damage to the dorsal pathway (where) couldn't reach for visual target, had optic ataxia

Question 47

thalamus as a relay station

Answer 47

LGN can maybe regulate neural information sent to the cortex since it receives more signals than it sends to the cortex. ● Feedback = backward/top-down flow of information: brain may send information to the LGN about how much information it wants to receive.

Question 48

Inferotemporal (IT) cortex

Answer 48

processes whole complex objects like patterns, faces, and objects . Signals from IT cortex do to structures in the medial temporal lobe (MTL).

Question 49

Medial temporal lobe (MTL)

Answer 49

Parahippocampal place area (PPA): specialized for indoor/ outdoor scenes but not recognition of faces or objects. Entorhinal cortex: Hippocampus: important for memory and visual perception of specific objects. Fusiform face area (FFA): below inferior temporal cortex, specialized for face recognition. effects of cortica