Oculomotor system - Ploner

Question 1

What is the oculomotor system in control of?

Answer 1

• premotor control of eye movements and its disorders

- can infer from the gaze their mental state

Question 2

In the normal function of eye movements there are 2 purposes. What are these?

Answer 2

1. to stabilize images of the environment on the fovea
2. to change images of the environment on the fovea –> move eyes to acknowledge new incoming visual information entering the visual field

Question 3

Which of the following are involved in stabilizing images of the enviro on the fovea?

A. saccades
B. vergence
C. fixation
D. vestibulo-ocular reflex
E. smooth pursuit

Answer 3

B. vergence
C. fixation
D. vestibulo-ocular reflex
E. smooth pursuit

Question 4

Which of the following are involved in changing images of the enviro on the fovea?

A. smooth pursuit
B. fixation
C. vergence
D. saccades
E. vestibulo-ocular reflex

Answer 4

D. saccades

Question 5

What does the vestibulo-ocular reflex do?

Answer 5

• it stabilizes images of the environment on the fovea by compensating for brief, quick head movements
• suppresses fixation
• at rest, R=L –> there is symmetry between the left and right part of the vestibulo-ocular system
• in a rightward turn, R>L –> asymmetry in neural input leads to a compensatory eye movement

Question 6

Which of the following are correct regarding what happens during a turn of the head?

A. right turn of the head = right compensatory movement of the eyes
B. the compensatory movement of the eyes will have the same speed and amplitude as the head movement
C. in a quick head rotation, there is a compensatory movement + a quick reset movement
D. in a slow head rotation, there is a compensatory movement + a quick reset movement

Answer 6

B. the compensatory movement of the eyes will have the same speed and amplitude as the head movement
D. in a slow head rotation, there is a compensatory movement + a quick reset movement

Question 7

What is ‘fixation’?

Answer 7

• the function to stabilize images of stationary stimuli on the fovea
• suppression of the vestibulo-ocular reflex

Question 8

What occurs in vestibulo-cerebellar syndrome?

A. impaired fixation suppression
B. impaired vestibulo-ocular suppression
C. nystagmus is not suppressed by fixation in these patients
D. inhibition by the cerebellum is not taking place

Answer 8

B. impaired vestibulo-ocular suppression
C. nystagmus is not suppressed by fixation in these patients
D. inhibition by the cerebellum is not taking place

Question 9

What occurs in gaze-evoked nystagmus?

A. constant drifting and correction when looking laterally
B. impairment in the nucleus fastigii and the vermis dorsalis
C. impairment of the nucleus vestibularis, nucleus praepositus hypoglossi, and flocculus
D. nystagmus with no apparent cause

Answer 9

A. constant drifting and correction when looking laterally

C. impairment of the nucleus vestibularis, nucleus praepositus hypoglossi, and flocculus

Question 10

What is true about smooth pursuit?

A. it is a quick simultaneous movement of both eyes between 2+ phases of fixation in the same direction
B. it is controlled by few brain structures
C. it stabilizes images of moving stimuli on the fovea

Answer 10

C. stabilizes images of moving stimuli on the fovea

Question 11

What are saccades?

Answer 11

• a quick simultaneous movement of both eyes between 2+ phases of fixation in the same direction
• change images of the environment on the fovea
• focus on something that has appeared in the periphery of the visual field

Question 12

What are the aspects of eye movements that are analyzed?

A. speed
B. velocity
C. amplitude
D. reaction time

Answer 12

B. velocity
C. amplitude
D. reaction time

Question 13

What does the prepontine paramediane RF (PPRF) do?

Answer 13

• provides a burst of activity that accelerates the eye

- damage in this area affects velocity

Question 14

What does the nucleus raphe interpos. (NRI) do? (when does it fire)

Answer 14

• fires when the eye does not move. Reciprocal inhibition to PPRF
• damage in this area leads to rapid machine-gun like movements –> like saccades

Question 15

Which of the following disorders results in a massive slowing in saccades, as a result of a problem in reticular formation?

A. vestibulo-cerebellar syndrome
B. parkinsonian syndromes
C. frontal lobe syndrome
D. pontine and mesencephalic syndromes

Answer 15

D. pontine and mesencephalic syndromes

Question 16

Hypometria of saccades is involved in vestibulo-cerebellar syndromes.

A. true
B. false

Answer 16

B. false

HYPERmetria of saccades is involved in vestibulo-cerebellar syndrome

Question 17

What eye movement is impaired in frontal lobe syndrome and what are the involved structures?

Answer 17

• impaired inhibition of reflexive saccades

- structures: eye fields, dorsolateral PFC