Eye Movements

Question 1

What are the functions of the vestibulo-ocular and optokinetic reflexes?

Answer 1

Keep the eyes still while the head moves

Question 2

What is the function of saccades?

Answer 2

Change what we’re looking at

Question 3

What is the function of pursuit and fixation?

Answer 3

Keep an object’s image focused on the fovea

Question 4

What is the function of vergence?

Answer 4

To change the plane of an object

Question 5

What direction of eye movements is the riMLF responsible for?

Answer 5

Vertical

Question 6

What direction of eye movements is the PPRF responsible for?

Answer 6

Horizontal

Question 7

What are the two pathways of the vestibulo-ocular reflex?

Answer 7

Direct: CN VIII nucleus–> CN VI contralateral
CN VI–> lateral rectus of contralateral eye
CN VI–> CN III
CN III–> Medial rectus of ipsilateral eye

Indirect: CN VIII –> Nucleus propostius hypoglossi (NPH)

Question 8

What is the function of the indirect vestibulo-ocular pathway (through the NPH)?

Answer 8

Low energy steady firing of the nerves to keep the eyes in position

Question 9

What is the optokinetic reflex based on?

Answer 9

Visual input (vs. vestibular input in vestibulo-ocular)

Question 10

What is the purpose of the optokinetic reflex?

Answer 10

Stabilize vision during slow or constant velocity head movement

Question 11

What are the two components of the optokinetic reflex movement?

Answer 11

Quick pursuit

Slow saccade

Question 12

Which of the following is constant and which is variable in saccades? Velocity, amplitude, direction

Answer 12

Velocity is constant

Amplitude and direction are variable

Question 13

What kind of stimuli triggers saccades?

Answer 13

Visual, auditory, or any other kind (tap on the shoulder)

Question 14

What is the function of frontal eye field (FEF)?

Answer 14

Directs brain stem to move eyes

Question 15

What is the function of supplementary eye field (SEF)?

Answer 15

Has learned sequences of saccades

Question 16

What’s the function of the prefrontal cortex?

Answer 16

The dorsolateral prefrontal cortex contains memories of objets and decision making about whether to look or not

Question 17

What’s the pathway of saccades starting from the FEF?

Answer 17

FEF–> internal capsule–> superior culliculus–> contralateral PPRF–> contralateral abducen nucleus
MLF carries signal to ipsilateral CNIII nucleus–> medial rectus

Question 18

What is the function of pause neuron in saccades?

Answer 18

Inhibits the PPRF from making a saccade

Question 19

What is the function of the inhibitory neuron?

Answer 19

Inhibits the pause neuron but also sends signal to ipsilateral (to frontal cortex) CNVI nucleus not to hold up the eye movement.

Question 20

What is the function of the parietal occipitotemporal area?

Answer 20

Provides velocity information to the FEF in pursuit movements

Question 21

What is the difference in relationship between FEF and the abducen nucleus in pursuit vs. saccades?

Answer 21

In saccades, the FEF sends information to the contralateral abducen nucleus, while in pursuit, it sends info to the ipsilateral nucleus

Question 22

What would be the effect of a cortical lesion on saccades?

Answer 22

Eyes would point towards the lesion (away from the hemiperesis)

Question 23

What would be the effect of pontine lesion on saccades (affecting the abducen nucleus)?

Answer 23

Eyes would point away from the lesion

Question 24

What would be the effect of a unilateral lesion affecting the MLF on saccades?

Answer 24

The ipsilateral eye would not be able to adduct during saccades or pursuit
It would be able to adduct during vergence