Ch 17: Optokinetic Eye Movements

Question 1

the purpose of the optokinetic eye movement class is to

Answer 1

keep the whole visual scene stable on the retina

Question 2

when we move through an environment, the images inside the eye may also move across the retina, this retinal motion is called

Answer 2

optic flow

Question 3

why are optokinetic eye movements activated

Answer 3

to move the eyes in an attempt to stabilize the image on the retina

Question 4

how can optokinetic eye movements affect motion blur?

Answer 4

when the optokinetic eye movements reduce the optic flow on the retina, they also make it less likely that motion blur will be experienced

Question 5

3 types of optic flow are

Answer 5

• radial
• linear
• rotatory

Question 6

head pitch and yaw yield what type of optic flow?

Answer 6

rotatory

Question 7

what types of flow provide optokinetic stimulus

Answer 7

only linear and rotatory

Question 8

describe optokinetic slow and quick phases

Answer 8

• slow phase is due to linear negative feedback tracking mechanism (it follows the target)
• quick phase is resting saccade

Question 9

optokinetic system temporal frequency characteristics are

Answer 9

low pass 
(cut off frequency less than 5Hz)

Question 10

optokinetic system velocity properties are

Answer 10

it responds best to slow object motion up to 30 degree/sec. the response is sustained (does not wear off)

Question 11

what occurs is there is a high velocity value in the optokinetic response

Answer 11

about 100 degrees/sec, system breaks down, response poor, unrelated to object motion. motion blurring occurs

Question 12

response of optokinetic response latency consists of what two phases

Answer 12

EOKN- early, responds to small objects (similarities to pursuit)
LOKN- late, requires large fields

Question 13

describe a situation where optokinetic afternystagmus occurs

Answer 13

observer watches a large moving field for some time and then is placed in darkness, the optokinetic nystagmus continues to occur

Question 14

why does the optokinetic afternystagmus occur and what is the phenomenon called

Answer 14

occurs due to an adaptive component that ‘stores’ object velocity and then releases it when the stimulus motion ceases

Question 15

change in optokinetic response gain with attention

Answer 15

with active looking, gain approaches 1

with passive staring, gain approaches 0.8

Question 16

temporal-to-nasal versus nasal-to-temporal response

Answer 16

temporal-to-nasal optokinetic response is slightly better

nasal-ward bias is highly pronounced in infants less than 12 weeks

Question 17

potential complements and conflicts with other classes and optokinetic

Answer 17

vestibulo-ocular complements
pursuit conflicts (optokinetic response must be suppressed during smooth pursuit)

Question 18

a large rotating field induces a pronounced illusory perception of self-motion in the opposite direction called

Answer 18

circularvection

Question 19

list 2 neural pathways for information in optokinetic response

Answer 19

1. accessory optic system and nucleus of optic tract

2. visual cortex V1 by LGN

Question 20

development of 2 neural pathways in OKR

Answer 20

1. accessory optic system AOS and nucleus of optic tract (NOT)- subtropical pathways that operate from birth
2. visual cortex V1 through lateral geniculate nucleus LGN and MT/MST is immature until about 12 weeks age

Question 21

NOT responds to only

Answer 21

ipsilateral optic flow stimuli from the contralateral eye

Question 22

MST area is involved in

Answer 22

motion detection, smooth pursuit, and optokinetic eye movements

Question 23

how are the cortical pathways different from the subcortical pathways

Answer 23

cortical pathways respond to motion in any direction from either eye
(the cortical pathways do not have monocular directional asymmetry)