Extra CH6 slides Midterm 2

Question 1

Receptive Field

Answer 1

The area of the visual field within which it is possible for a visual stimulus to influence the firing of a given neuron. By increasing or decreasing AP.

Question 2

Hubel and Wiesel

Answer 2

looked at receptive fields in cat retinal ganglion, LGN, and striate cortex
Insert microelectrodes and look at patterns of light on cats retina; found in retina, thalamus and striate cortex

Question 3

Many cells have receptive fields with a center-surround organization:

Answer 3

excitatory and inhibitory regions separated by a circular boundary

Question 4

On-centre cell with receptive field

Answer 4

In the middle when lights are on and in the outer circle when lights are off.
Flashing small bright spot in the center subregion increases the cell’s response. Flashing a bright annulus in the surround subregion inhibits the cell’s response. There is little or no response to a large (full field) spot of light that covers both the center and the surround because excitation in the center cancels the inhibition from the surround, called lateral inhibition.

Question 5

Off-centered cell with receptive field

Answer 5

In the middle when lights are off and in the outer circle when lights are on
An OFF-center/ON-surround ganglion cell has the opposite arrangement. It gets inhibition from a small spot of light in the center, and excitation from an annulus in the surround.

Question 6

Receptive Fields in Striate Cortex

Answer 6

In most of the striate cortex, neurons with circular receptive fields (as in retinal ganglion cells and LGN) are rare
Most neurons in V1 are orientation sensitive; they respond best to a line of a particular orientation

Question 7

Simple neurons in V1

Answer 7

Simple- receptive fields are rectangular with “on” and “off” regions, orientation and location sensitive and
all are monocular

Question 8

Complex neurons in V1

Answer 8

also rectangular, larger receptive fields, respond best to a particular stimulus anywhere in its receptive field. Can move and fire no matter where as long in same orientation(Not location sensitive but is orientation sensitive). Many are binocular,
Motion sensitive

Question 9

Organization of V1: Cortical columns

Answer 9

Neurons in the same column respond to stimuli applied to the same area of the retina.
Each column is sensitive to a specific region of the visual field.
This allows for retinotopic organization to be maintained

Question 10

Component theory (trichromatic theory)

Answer 10

Proposed by Young, refined by Helmholtz
Three types of receptors, each with a different spectral sensitivity
Blue(short), green(medium), red (long)
Each of the cones have their won spectral sensitivity curve
You can have combinations of cone receptors to see different colours
Medium+long=orange

Question 11

Colour-Deficient Vision

Answer 11

People who suffer red-green blindness have trouble perceiving the number within the design (the 74 picture)
Cone defecting
More common men, the genes responsible for red-green vision is on the X chromosomes. If you have a defective chromosome as a man that cannot be replaced so they can have this trouble.

Question 12

Colour Blindness

Answer 12

Cone pigment is missing

Question 13

Protanopia

Answer 13

An inherited form of defective color vision in which red and green hues are confused; “red” cones are filled with “green” cone opsin
They see the world in shades of yellow and blue; both red and green look yellowish to them
Visual acuity is normal

Question 14

Opponent-process theory

Answer 14

Proposed by Herring
Two different classes of cells encoding colour, and another class encoding brightness
Each encodes two complementary colour perceptions
Red-green; blue-yellow; black-white

Question 15

Receptive Fields of color-sensitive ganglion cells:

Answer 15

Activation of one member of the pair inhibits activity in the other.
Blue; yellow, Red; green

Question 16

Component and Opponent Processing

Answer 16

Coding of colour by cones seems to operate on a purely component basis
Opponent processing of colour is seen at all subsequent levels of the retina-geniculate-striate system
Both are correct

Question 17

Flow of visual information:

Answer 17

Thalamic relay neurons, to
1˚ visual cortex
2˚ visual cortex
Visual association cortex

Question 17

Flow of visual information:

Answer 17

Thalamic relay neurons, to
1˚ visual cortex
2˚ visual cortex
Visual association cortex

Question 18

As visual information flows through hierarchy, receptive fields:

Answer 18

become larger as info goes anteriorly
respond to more complex and specific stimuli

Question 19

Dorsal stream:

Answer 19

pathway from primary visual cortex to dorsal prestriate cortex to posterior parietal cortex
The where pathway (location and movement),
Pathway for control of behavior (e.g., reaching)

Question 20

Ventral stream:

Answer 20

pathway from primary visual cortex to ventral prestriate cortex to inferotemporal cortex
The “what” pathway (colour and shape), or
Pathway for conscious perception of objects

Question 21

Patient D.F. – Visual Agnosia

Answer 21

Cannot tell what the object is
Ventral visual impairment
Sometimes with touch they can identify the object

Question 22

Optic Ataxia

Answer 22

the inability to accurately point to or reach for objects under visual guidance with intact ability when directed by sound or touch despite normal strength
Dorsal visual impairment

Question 23

Movement Perception and Area V5/MT

Answer 23

Cells in V5/MT respond to particular directions of movement
Moving dots compared to static dots

Question 24

Motion Blindness: Akinetopsia

Answer 24

Patient L. M.
World appears as a series of snapshots
Does not perceive continuous motion
Inability to judge direction and speed

Question 25

Fusiform Face Area (FFA)

Answer 25

FFA responds more strongly to faces than to other category of objects.

Question 26

Prosopagnosia

Answer 26

impairment in face recognition; associated with damage to FFA
De Renzi (1986) – patient failed to recognize his own family but could do so by voice, clothes, etc., “are you…? [wife’s name] I guess you are my wife because there are no other women at home, but I want to be reassured”

Somewhat controversial