Lecture 13 Objectives

Question 1

What are the three characteristics of smooth pursuits?

Answer 1

Latency
Velocity
Gain

Question 2

What is the latency of smooth pursuits?

Answer 2

100-300msec

Question 3

Is smooth pursuit latency shorter or longer than saccade latency?

Answer 3

Shorter

Question 4

Which eye movements have the longest latency?

Answer 4

Saccades

Question 5

What affects the pursuit latency period?

Answer 5

Target saliency:
Higher contrast
Better illumination
More color
These decrease latency

Question 6

What is the velocity of smooth pursuits?

Answer 6

0.1 to 70 degrees per second

Question 7

What is the formula for smooth pursuit gain?

Answer 7

Gain = peak eye velocity / peak target velocity

Question 8

What is ideal gain?

Answer 8

1.0

Question 9

Smooth pursuit of a predictable target is ___ than of a non-predictable target.

Answer 9

Better

Question 10

What are the three factors that affect pursuit gain?

Answer 10

Prediction
Adaptation
Fatigue

Question 11

For a predictable target in view for more than 1 second, what would the expected gain be?

Answer 11

1.0

Question 12

If a target’s movement is brief, and there isn’t time to predict its path, what would the expected gain be?

Answer 12

0.9

Question 13

What are the two phases of control for pursuits?

Answer 13

Open loop (initiation)
Closed loop (maintenance)

Question 14

The open loop phase of pursuits occurs when?

Answer 14

During the initiation of pursuits, starting during the latency period

Question 15

What guides the open loop phase of pursuits?

Answer 15

Target motion

Ex. retinal slip velocity

Question 16

Does the initial acceleration of pursuits depend on initial target velocity?

Answer 16

No

Question 17

What occurs during the closed loop phase of pursuits?

Answer 17

The brain adds an extraretinal feedback of eye velocity to retinal slip velocity in order to compute the target velocity

Question 18

What structures are involved in the higher level control of pursuits?

Answer 18

Middle Temporal Cortex (MT)
Medial Superior Temporal Cortex (MST)
Frontal Eye Field Pursuit Subregion (FEFsem)
Dorsolateral Pontine Nucleus (DPN)

Question 19

What is the function of the MT in pursuits?

Answer 19

Processes retinal motion

Question 20

What is the function of the MST in pursuits?

Answer 20

Processes egocentric motion

Question 21

What is the function of the FEFsem in pursuits?

Answer 21

Initiation, steady state, and predictive aspects of smooth pursuits

Question 22

What is the function of the DPN in pursuits?

Answer 22

Encodes the horizontal velocity of the fixation target and the eye

Question 23

A lesion in which part of the brain will cause a scotoma of motion?

Answer 23

V1 or MT

Question 24

What does a scotoma of motion cause?

Answer 24

Decreased smooth pursuit speed

Dysmetric saccades in all directions of the contralesional hemifield

Question 25

What does a lesion of the MST cause?

Answer 25

Directional pursuit deficits

Question 26

With a lesion of the MST, there will be impaired horizontal pursuit toward what?

Answer 26

The side of the lesion

Question 27

T or F: Saccades are affected by lesions in the MST.

Answer 27

False