Module 6.2

Question 1

Axons of which cell form the optic nerve?

Answer 1

ganglion cells

Question 2

What is the name of the site which the right and left optic nerves meet?

Answer 2

optic chiasm

Question 3

Where do most axons in optic nerves synapse?

Answer 3

lateral geniculate nucleus

Question 4

What is the destination of axons from the later geniculate nucleus?

Answer 4

other parts of the thalamus and the occipital cortex

Question 5

What is lateral inhibition?

Answer 5

Lateral inhibition is when one cell inhibits another cell’s activity.

Question 6

How does lateral inhibition enhance contrast?

Answer 6

It enhances contrast by increasing sensory perception.

Question 7

Describe parvocellular ganglion cells.

Answer 7

Parvocellular gangion cells have small receptive fields and are sensitive to color and details.

Question 8

How do parvocellular ganglion cells differ from magnocellular ganglion cells?

Answer 8

Magnocellular ganglion cells have larger receptive fields and are movement sensitive, and are not color sensitive.

Question 9

What is a receptive field of a cell in the visual system?

Answer 9

the part of the field that inhibits or excites it

Question 10

What happens at the optic chiasm?

Answer 10

Half of the axons from ganglion cells cross to the opposite hemisphere

Question 11

Describe the evidence that Area V1 is necessary for conscious vision.

Answer 11

People with damage to the Area V1, report no conscious vision, no visual imagery, and no visual images.

Question 12

What is blindsight?

Answer 12

the ability for a person to respond to visual info that they report not seeing

Question 13

What are two potential explanations for blindsight?

Answer 13

One explanation is that the other branches of the optic nerve deliver visual info to the supior colliculus and other areas, so maybe one of those parts controls the blindsight responses. Another explanation is that tiny bits of healthy tissue remain within an otherwise damaged visual cortex that provides enough perception for blindsight

Question 14

In what cortical area does the dorsal stream end?

Answer 14

parietal cortex

Question 15

What is the dorsal stream’s functional contribution to vision?

Answer 15

It helps the motor area find and use objects

Question 16

For what accomplishment did Hubel and Wiesel win the Nobel Prize?

Answer 16

They used microelectrode recordings to to study individual cells and they distinguished several types of cells in the visual cortex.

Question 17

Describe the receptive fields of simple cells.

Answer 17

they have fixed inhibitory and excitatory zones

Question 18

What is the major difference between the responses of simple and complex visual cortical cells?

Answer 18

Simple cells respond to the exact location of a stimulus, complex cells do not.

Question 19

Describe the receptive field of a hypercomplex cell.

Answer 19

It has a strong inhibitory area at one end of its receptive field.

Question 20

What is a feature detector?

Answer 20

Neurons whose responses indicate the presence of a particular feature

Question 21

Are neurons in area V1 feature detectors?

Answer 21

No

Question 22

Describe the evidence for and against area V1 neurons being feature detectors.

Answer 22

The evidence suggesting Area V1 neurons are feature detectors is that they respond strongly to bar- or edge-shaped patterns. The evidence against area V1 neurons being feature detectors is cortical cells, who also respond well to a single bar or line, responds more strongly to a spatial frequency

Question 23

Which areas, beyong V1, are important for shape analysis? What are their contributions?

Answer 23

The inferior temporal cortex is important for shape analysis. It detects objects, but not the amount of light or dark on the retina.

Question 24

What is shape constancy?

Answer 24

the ability to recognize an object’s shape even as it changes position, angle, and lighting

Question 25

What is visual agnosia?

Answer 25

an inability to recognize objects despite otherwise good visioin

Question 26

What is prosopagnosia?

Answer 26

the inability to recognize faces

Question 27

What area in the inferior temporal lobe increases its activity when people with intact brains recognize faces?

Answer 27

fusiform gyrus

Question 28

What appears to be a special function of V4?

Answer 28

color constancy

Question 29

Which 2 areas of the cortex are specialized for motion perception?

Answer 29

MT (middle-temporal cortex or area V5) and MST (medial superior temporal cortex)

Question 30

How do MT cells respond?

Answer 30

When something moves at a particular speed in a particular direction

Question 31

What are the preferred stimuli for cells in the dorsal part of area MST?

Answer 31

complex stimuli

Question 32

What is the role of ventral MST cells?

Answer 32

To repsond to an object that moves relative to its background

Question 33

Why don’t we see a blur when we move our eyes?

Answer 33

Because several of the visual areas of your brain decrease their activity during voluntary eye movements

Question 34

What is a saccade?

Answer 34

a ballistic movement of the eyes from one fixation point to another

Question 35

Describe motion blindess.

Answer 35

the ability to see objects but not being able to see if they are moving or how fast and in what direction an object is moving

Question 36

What causes motion blindness?

Answer 36

damage to the MT