Dorsal Stream and the Dress (F)

Question 1

What is the idea that your vision can tell you about motion, but only within a certain range of speeds?

Answer 1

perception of change

Question 2

What controls our perception of size and experiences size illusions?

Answer 2

ventral stream

Question 3

What controls our interaction with objects? 1. What is this stream’s perception of size more like? 2

Answer 3

1. dorsal stream

2. veridical (true), less likely to have illusions

Question 4

What can damage to the dorsal stream disrupt in terms of perception of objects in space?

Answer 4

1. oculo-centric space
2. head-centered space
3. ego-centric space

Question 5

What is abnormal motion perception where the patient sees stationary “slide show” instead of motion called? 1. What is damaged in this case? 2

Answer 5

1. akinetopsia

2. MT/V5

Question 6

What is damage in Balint-Holmes syndrome? 1. What is the triad of findings? 2

Answer 6

1. parietal lobe(s), part of dorsal stream (can be unilateral)
2. optic ataxia (disordered reaching), gaze paralysis, and simultagnosia (can’t see more than one thing at a time)

Question 7

What coordinate system is lost in Balint-Holmes syndrome?

Answer 7

egocentric spatial coordinates

Question 8

What is disordered reaching called?

Answer 8

optic ataxia

Question 9

What is not being able to see more than one thing at a time called?

Answer 9

simultagnosia

Question 10

What is thought to be involved in controlling the initiation of saccades under visual attention? 1. What happens when this area is lesioned? 2

Answer 10

1. posterior parietal cortex

2. long-latency saccades (gaze paralysis)

Question 11

What are the pathways to the dorsal stream that are still intact when V1 is damaged (blindsight)?

Answer 11

1. retina to pulvinar to dorsal stream
2. retina to superior colliculus to pulvinar to dorsal stream
3. retina to konio to dorsal stream

Question 12

Patient G.Y. that had damage to V1 at age 8, now has stronger connections than normal between what structures of the brain?

Answer 12

LGN to MT/V5

Question 13

What are the dorsal stream capabilities in blindsight patients?

Answer 13

1. reaching for objects within ego-centric space
2. detecting motion and understanding the direction of moving objects
3. locomotion/mobility within egocentric space

Question 14

What is the inability to use everyday tools or to carry out skilled, purposeful motor behavior called?

Answer 14

apraxia (dorsal disorder)

Question 15

What is the inability to use a pencil to draw or copy pictures such as 2D or 3D geometrical shapes, or interlocking figures called? 1. What is this common in? 2. What area of the brain is damaged? 3

Answer 15

1. constructional apraxia
2. Alzheimer’s disease
3. parietal

Question 16

What is the patient still able to do regarding the object presented in constructional apraxia?

Answer 16

1. recognize what is illustrated (not apperceptive agnosia)
2. know what it is (not object agnosia)
3. knows what the overall scheme is (not simultagnosia)

Question 17

What is it called when a patient cannot understand items on the neglected side and does not interact with them? 1. Where is the lesion? 2. What is it often due to? 3

Answer 17

1. visual neglect (hemi-neglect, unlateral neglect)
2. effect contralateral (usually left side) to lesion (usually right side) in parietal lobe
3. stroke in Middle Cerebral artery

Question 18

What test is run on all children in our clinic for a full eye exam to evaluate their visual perception?

Answer 18

visual-motor integration test (VMI)

Question 19

Which develops later according to some investigators, the ventral or dorsal stream?

Answer 19

dorsal stream

Question 20

How does the camera impact the coloration of “the dress”?

Answer 20

camera makes assumption about the illuminant and adjusts colors to make white white (according to it)

Question 21

What does the human vision use to determine if the illuminant assigned by the camera to the photo is correct?

Answer 21

the coloration of the skin of the person

Question 22

What is the main issue with the camera sensors that makes it difficult for it to determine the spectral composition compared to the human eye?

Answer 22

RBG sensors don’t overlap in cameras like they do in humans

Question 23

What is the constant appearance of surface color properties even though the illuminant varies widely called?

Answer 23

color constancy

Question 24

What are the ideas to explain why color constancy occurs?

Answer 24

1. using the brightest part of the image to determine what the illuminant is
2. using the average of the image to determine what the illuminant is (assuming gray world)

Question 25

What are people who see the dress as blue doing? 1. As white? 2

Answer 25

1. trying to judge the “light itself” (light arriving at eye) so seeing at as in daylight
2. trying to judge the “dress itself” (spectral reflectance of the cloth) so seeing it as in shade