8. Eye Movements 1 & 2

Question 1

Eye movement is the movement of?

Answer 1

Movement of the brain itself because the eye is not a peripheral organ.

Question 2

Retina is what type of tissue?

Answer 2

Brain tissue

Question 3

Do eye muscles have monosynaptic strech reflex?

Answer 3

No

Question 4

What does each movement have in unique?

Answer 4

Each EM has its own function, stimulus, anatomic & physiological pathway.
Also, this movements can occur simultaneously at the same time.

Question 5

What is saccade?

Answer 5

The fastest eye movement that can be made. Hence, to record saccades a high sampling rate is required.

Question 6

Eyes have how many muscles?

Answer 6

6 muscles that exists in pairs.

Question 7

How many axis for eye movements?

Answer 7

3 axes
1. Vertical axis- movement of eyes horizontally.
2. Horizontal axis- movement of eyes vertically.
3. Visual axis- along the fovea at the centre of the pupil, controls torsion of the eye.

Question 8

2 overall functions of eye movements?

Answer 8

1. Maintain a stable view of the world
2. Redirect the line of sight

Question 9

What are the 2 compensatory (Reflective eye movements)? And the role of this movements?

Answer 9

VOK & OKN
Role: correct eye movements to keep the view stable

Question 10

Saccades meaning?

Answer 10

Change in gaze independent to head orientation.

Question 11

Smooth pursuit movement?

Answer 11

Follow a (Slowly) moving target.

Question 12

Vergence meaning?

Answer 12

Enlarge binocular field/ reduce disparity.

Question 13

3 eye movements that redirect line of sight (Fovea)

Answer 13

Saccades, smooth pursuit & vergence

Question 14

Vergence is said to be the only disjunctive eye movement, what does this mean?

Answer 14

eyes move in opposite directions

Question 15

Effect of inertial mass on eye movements humans vs birds

Answer 15

Humans have a smaller inertial mass of eyes compared to birds. Hence, in birds the head moves to create movements whereas in humans eyes move.

Question 16

Primates have frontally faced eyes but animals have laterally orientated eye, hence they require a special system to main stable gaze. what is the special system for birds?

Answer 16

Head bobbing in birds

Question 17

Influence of eye movements?

Answer 17

Disturbance to the stable view of the world

Question 18

Land’s observation?

Answer 18

All animals have the same five visuomotor movements.

Question 19

Mittelstaedt’s hypothesis?

Answer 19

Saccadic systems are designed to localize objects in space.

Question 20

Most eye movements are conjugate- what does this mean?

Answer 20

Eyes moves together

Question 21

What is the relationship between head movements?

Answer 21

Gaze

Question 22

Stability of vision is the same as stability of gaze- what does this mean?

Answer 22

This is the stability gaze that is stability of retinal image on the fovea

Question 23

3 Classifications of eye movements?

Answer 23

1. Compensatory/ stabilizing OR targeting.
2. Conjugate or disjunctive
3. Visual vs non- visual stimulus (VOR)

Question 24

2 Compensating eye movements?

Answer 24

VOR - Vestibulo-ocular reflex
OKN- Optokinetic Nystagmus

Question 25

3 Targeting movements?

Answer 25

Saccades, Smooth Pursuit and Vergence

Question 26

Which eye movement has no visual stimulus?

Answer 26

VOR

Question 27

Role of VOR

Answer 27

Stabilises gaze ensuring clear vision during head movements. It is non-visual stimulus

Question 28

Non-visual stimulus is driven by?

Answer 28

Afferent signals from the inner ear canals.

Question 29

VOR compensates for?

Answer 29

fast, transient head movements

Question 30

VOR takes place in what light conditions?

Answer 30

Dark and light

Question 31

Which system kicks in when trying to maintain a stable gaze?

Answer 31

VOR

Question 32

VOR is unconscious or conscious?

Answer 32

Unconscious

Question 33

VOR driven by which system?

Answer 33

Vestibulo system

Question 34

VOR nystagmus meaning

Answer 34

The eyes are trying to maintain stable gaze for as long as possible THEN it snaps- this is called slow & fast phase.

Question 35

What is the fastest movement made in terms of latency?

Answer 35

VOR

Question 36

Implications of large head movements and fast movements?

Answer 36

Large head movements, beyond limit leads to fast phase correction. Fast movements cause retinal slip- Because VOR IS not compensating for complete head movements.

Question 37

Slow vs fast phase eye movements in relation to head movements?

Answer 37

Slow phase: opposite direction to head movement. Fast phase: same direction to head movements.

Question 38

OKN Role?

Answer 38

Stabilizes gaze ensuring clear vision during movements of the visual field (world).

Question 39

Visual stimulus of OKN?

Answer 39

Retinal slip or Optic flow

Question 40

OKN compensates for?

Answer 40

Fat and transient movements

Question 41

OKN has a speed limit?

Answer 41

Yes OKN can not compensate for very very fast motion

Question 42

OKN generates slow phase movements in which direction?

Answer 42

Slow phase movements generated in the same direction and velocity as perceived retinal slip.

Question 43

When OKN reaches its maximum limit it produces?

Answer 43

Quick "reset" phase called saccade

Question 44

Saccades or Pursuits - which movement needs a stimulus?

Answer 44

Saccades do not require a stimulus. They can also be made from memory. Pursuit needs a stimulus.

Question 45

Ballistic movement?

Answer 45

React to 1 stimulus at a time, then a refractive period (i.e., latency period).

Question 46

Main sequence?

Answer 46

Correlation between amplitude, duration and velocity. This sequence is used to compare normal Px’s with abnormal Px’s.

Question 47

Saccadic suppression?

Answer 47

Inability to see anything during a saccade.

Question 48

When a saccade is executed there is suppression of?

Answer 48

Conscious vision in V1

Question 49

Relation between duration and amplitude of saccade?

Answer 49

Linear relationship

Question 50

Relationship between peak velocity and saccadic amplitude exists because?

Answer 50

Because of action potential of motor neurons driving the muscles making the saccade.

Question 51

Duration and velocity of a saccade is driven by?

Answer 51

Duration- bust of firing in the motor neuron Velocity- by the frequency of action potential

Question 52

Saccadic suppression is suppression of?

Answer 52

Low spatial frequency

Question 53

Saccadic suppression involves which pathway?

Answer 53

Magnocellular at LGN

Question 54

Which system is suppressed in smooth pursuit?

Answer 54

OKN

Question 55

Smooth pursuit is driven by?

Answer 55

vestibular NUCLEUS

Question 56

Slowest eye movement is?

Answer 56

Vergence

Question 57

How can the speed of vergence be increased

Answer 57

If combined with saccades

Question 58

Stimuli for vergence?

Answer 58

-Blur = accommodative vergence (provoked by changing lens) -Disparity = fusional vergence (provoked by changing prism)

Question 59

Retinal ques that provoke accommodative response?

Answer 59

Objects temporal to the fovea- interpreted as closer, nasal to the fovea- interpreted as far.

Question 60

Parallax is?

Answer 60

Non-retinal que on distance of objects

Question 61

Visuomotor control is restricted by how many axes?

Answer 61

3

Question 62

How does the brain identify if change in retinal image is due to objective motion or subjective motion?

Answer 62

Brain has a system called efference control center. The brain gets a copy of efference output which is compared against retinal shift.