Visual Motor System

Question 1

The abducens nucleus contains 2 pools of neurons:

Answer 1

abducens LMN, abducens interneurons projecting to contralateral MLF

Question 2

Lesion to Abducens nucleus or MLF produces ______ and results in ______.

Answer 2

middle alternating hemiplegia, medial strabismus

Question 3

Patient with damage to CN IV or MLF have these symptoms:

Answer 3

affected eye drifts up and extorts, these patients often tilt their head to the side opposite the affected eye

Question 4

Patients with damage to CN III, CN III nucleus, or MLF have these symptoms:

Answer 4

ptosis, mydriasis, and an eye that drifts down and out

Question 5

Voluntary saccades initiated in ______.

Reflexive saccades initiated by __________.

Answer 5

cortical eye fields, superior colliculus

Question 6

Brainstem vertical gaze center is made up of the ______ and the ________ which are immediately adjacent to the ______ and the _______ nucleus.

Answer 6

interstitial nucleus of Cajal, Rostral interstitial nucleus of the MLF, periaqueductal gray, red nucleus

Question 7

The brainstem horizontal gaze center is made up of the _________ which is immediately adjacent to the _______ in the pons.

Answer 7

paramedian pontine reticular formation (PPRF), MLF

Question 8

Saccadic movements require actions or lack of action from each of these 4 cell groups in the brainstem gaze centers:

Answer 8

omnipause, excitatory burst neurons (EBN), Inhibitory burst neurons (IBN), tonic cells

Question 9

___________ neurons are active just prior to agonist release and are located in the PPRF.
________ neurons are active just prior to inhibition of antagonists and are located in PPRF.
_______ cells maintain new gaze position and are located in the _______________.

Answer 9

Excitatory burst (EBN), Inhibitory burst (IBN), tonic cells, nucleus prepositus hypoglossi (in caudal pons).

Question 10

Sequence of events for horizontal saccade (3 events):

Answer 10

1. omnipause cells suppressed
2. EBN cells trigger abducens nucleus
3. IBN cells inhibit other abducens nucleus
4. tonic cells maintain new gaze (omnipause resume activity)

Question 11

__________ is dominant in non-reflexive saccades and projects to the horizontal and vertical gaze centers and the superior colliculus.

Answer 11

frontal eye field

Question 12

The abducens nucleus projects to the left occulomotor nucleus via the _______.

Answer 12

MLF

Question 13

Smooth pursuit is/isn’t voluntary.

It relies on the ________ to activate extraocular nuclei.

Answer 13

isn’t, vetibulocerebellum

Question 14

lesions to the vestibulocerebellum cause deficits in ________.

Answer 14

smooth eye movements

Question 15

Actions of the eye during vergence (focusing on target moving closer, or focussing on new target at different distance)

Answer 15

bilateral medial rectus, ciliary muscle contraction, constrictor pupillae (increase depth of field)

Question 16

The _______ is located in the _______ and is adjacent to the Edinger-Westphal preganglionic nucleus. It is responsible for coordination of vergence movements. It projects to the _____ nucleus to to coordinate parasympathetic changes in shape of lens and pupil.

Answer 16

supraoccular-motor area, midbrain, EW