Pursuit Eye Movements

Question 1

Ocular pursuit of the eye appeared late in the course of evolution and followed appearance of ___ which exists in primates (and reptiles)

Answer 1

the fovea

Question 2

Which species have two fovea?

Answer 2

birds

Question 3

Which species have an area centralis with more cones but more rods overall

Answer 3

cats/dogs (night vision)

Question 4

T/F we can track an object without a fovea

Answer 4

false

Question 5

How do species without a fovea track movement?

Answer 5

saccades

Question 6

What is the negative feedback in pursuits?

Answer 6

inhibitory closed loop, uses image motion as central command to efferent pathway

Question 7

T/F pursuits can modify themselves while movement is still going on

Answer 7

true

Question 8

Which has more complex neurology, pursuits or saccades?

Answer 8

pursuits

Question 9

How does negative pursuit feedback correct for too fast or too slow?

Answer 9

too fast– slow eye movement, too slow–put in corrective saccade to keep up

Question 10

How does the visual system know if the pursuit is accurate?

Answer 10

compare target motion and image motion on the retina

Question 11

What are the solid and dashed lines on the pursuit model diagram?

Answer 11

solid–flow of neural signals

dashed–physical events

Question 12

What is the positive feedback in pursuits?

Answer 12

eye velocity; helps get a sense of the degree of error

Question 13

Where does the afferent pathway info go?

Answer 13

summative area, like neural integrator

Question 14

When does the efferent pathway of a pursuit begin?

Answer 14

once target velocity has been reconstructed following eye velocity positive feedback

Question 15

When does pursuit command happen?

Answer 15

After positive feedback and efferent pathway

Question 16

What are the 3 afferent pathways?

Answer 16

retinal acceleration error, retinal velocity error, and retinal position error

Question 17

How long is the delay between target motion and afferent pathways?

Answer 17

90 msec

Question 18

T/F afferent pathways need to be summed before going to efferent pathways?

Answer 18

true

Question 19

As target velocity increases, pursuit gain…

Answer 19

decreases; especially in older population

Question 20

Where do young people start to see a decrease in pursuit gain?

Answer 20

40-50 deg/sec drops to gain of .9-.8

Question 21

When do older people decrease pursuit gain to 0.8

Answer 21

target velocity of 10 deg/sec

Question 22

What is pursuit latency?

Answer 22

time take from the decision to move to the beginning of the actual movement

Question 23

What is pursuit latency for fast targets?

Answer 23

100 milliseconds +/- 5 msec

Question 24

What is pursuit latency for slow targets (less than 5 degrees per second)?

Answer 24

up to 125 msec

Question 25

In general, the slower the pursuit, the longer the...

Answer 25

latency

Question 26

Rank the latency of eye movements from lowest to highest

Answer 26

VOR, pursuit, vergence, saccades

Question 27

Rank the velocity of eye movements from fastest to slowest

Answer 27

saccades, VOR, pursuit, vergence

Question 28

What is the latency of a smooth pursuit?

Answer 28

100-125 msec

Question 29

What is the velocity of a pursuit?

Answer 29

80 deg/sec

Question 30

What is the latency of a saccade?

Answer 30

200 msec

Question 31

What is the velocity of a saccade?

Answer 31

1000 deg/sec

Question 32

What is the velocity of VOR?

Answer 32

300 deg/sec

Question 33

What is the latency of VOR?

Answer 33

15 msec

Question 34

What is the latency of vergence?

Answer 34

160 msec

Question 35

What is the velocity of vergence?

Answer 35

10 deg/sec

Question 36

How long can eye velocity match stimulus velocity?

Answer 36

to 80 deg/sec

Question 37

Gaze orientation was one of the first functions that required the development of a brain that could...

Answer 37

predict, be curious, and simulate action

Question 38

What two things allow for pursuits?

Answer 38

cortical development and precise foveal function

Question 39

What is taxis?

Answer 39

orientation towards a sensory source ex: phototaxis, heliotaxis, thermotaxis, etc

Question 40

What four things does gaze orientation encompass?

Answer 40

projection, questioning, visualization, and prediction

Question 41

Berthoz says gaze orientation is

Answer 41

stationary locomotion

Question 42

What are the two frames of reference?

Answer 42

egocentric and allocentric

Question 43

What is egocentric?

Answer 43

reference is relative to self

Question 44

What is allocentric?

Answer 44

reference is relative to objects in the environment

Question 45

Which frame of reference develops first?

Answer 45

egocentric

Question 46

How does a baby direct its gaze?

Answer 46

using the body and turning head and eyes about its body axis

Question 47

Before 18 months babies fixate on

Answer 47

a landmark to which they anchor their progression around the room

Question 48

What is the first sign a baby is constructing allocentric relationships?

Answer 48

locating an object in the environment

Question 49

What happens if an baby's anchor point is hidden?

Answer 49

reverts back to egocentric strategy

Question 50

After 18 months an infant can...

Answer 50

mentally update his position in the room while he is walking, employing mechanism of mental rotation and translation

Question 51

T/F the intervention of high-level cognitive mechanisms in adaptation to sensory conflicts is really a problem of frames of reference

Answer 51

true

Question 52

What is one of the most important aspects of adaptation?

Answer 52

ability to move from one frame of reference to another and to combine them

Question 53

What do patients need to relearn after VOR lesion?

Answer 53

how to move from one frame of reference to another

Question 54

What is maximum eye velocity for pursuits?

Answer 54

80 degrees/sec

Question 55

What happens if target motion is faster than 80 degrees/sec?

Answer 55

need saccades to get back on target; older=more catch-up saccades

Question 56

What is natures way around the slowness of pursuits?

Answer 56

prediction

Question 57

Why is batter unable to maintain tracing when ball is at close distance?

Answer 57

high angular velocity

Question 58

The faster the pitch...

Answer 58

the farther away from home plate your eyes can accurately track the ball

Question 59

What are 3 strategies batters use to track a ball?

Answer 59

track w/ eye movements only and fall behind the last 10 feet; track with head movements and pursuits and fall behind in last 5 feet; use pursuits, then saccade to predicted point, continue to follow with peripheral vision, and resume smooth pursuit tracking at end with ball's image on fovea

Question 60

T/F batters use vergence eye movements

Answer 60

false

Question 61

Describe the flight of the baseball in thirds

Answer 61

1/3 batter forms mental model of trajectory, 2/3 observe difference b/w actual and mental, update mental and finalize swing, 3/3 observe errors in mental model to better track the next pitch

Question 62

Superstars have success because:

Answer 62

faster pursuit, ability to suppress VOR, anticipatory saccades, prediction

Question 63

How do we quantify quickness?

Answer 63

latency of saccadic eye movement system and eye-hand reaction time-- lab only not clinic

Question 64

What is zero-latency tracking?

Answer 64

overcoming time delay and tracking predictable targets with no delay provided the target position waveform is smooth and predictable with frequency b/w 0.1 and 1.0 Hz with small accelerations

Question 65

What does the time to collision concept relate

Answer 65

T=relation b/w observed diameter of the car in front which you are approaching and the speed with which this diameter expands

Question 66

If movement proceeds at constant velocity, time to collision can be evaluated by...

Answer 66

speed with which the retinal image of the object expands

Question 67

Time to contact is given solely by...

Answer 67

retinal cues

Question 68

How does our hand adapt its shape to the apparent shape of an object before contact?

Answer 68

we sample, calculate, and open change then change shape without conscious thought

Question 69

T/F the muscular activity of the arm is always initiated at the same time (before contact), no matter what the velocity of the target

Answer 69

true

Question 70

T/F the hand always take the shape of the object we are about to catch at the same distance from the hand

Answer 70

false-- just happens at the same time before catching no at the same distance from the hand

Question 71

How does tennis relate to time to collision?

Answer 71

the movement of the racket is constant and independent of the approach velocity, thus the beginning of the movement may in fact be adjusted by the value of the T margin-- adjust based on calculation of retinal slip made internally

Question 72

How much time is needed to estimate distance/time to contact?

Answer 72

need 240-300 msec to catch a ball

Question 73

To catch a ball traveling at 10 meters per second, the athlete has a temporal window of ___ during which his hand can remain closed

Answer 73

50 msec

Question 74

Catching a ball is preceded by __ that prepares for impact and is followed by a ___ induced by the impact

Answer 74

anticipatory muscular activity, reflex activity

Question 75

Subjects seem to base their response, whether anticipation or reflex on...

Answer 75

prediction of the dynamic properties of the ball under the influence of gravity