Nerves/VOR

Question 1

Vestibular N.
- Resting firing rate

Answer 1

90º spikes per second

Question 2

Vestibular N. for horiztonal canal
- Excitation and increased firing rate…

Answer 2

Ipsilateral to head motion

Question 3

Vestibular N. for horiztonal canal
- Inhibition and decreased firing rate…

Answer 3

Contralateral to head motion

Question 4

What is more important when sensing head motion?

Answer 4

Difference between nerves

Question 5

Vestibular N. for Poster and Anterior Canals
- Same rules apply but excitation or inhibition depend on what?

Answer 5

Plane and direction of motion

Question 6

Example:
Right Posterior Canal will be excited when?

Answer 6

Backwards and 45º to R

Question 7

Control of eye muscles when we move our head
What is this called?

Answer 7

Gaze stabilization/VOR

Question 8

What is VOR?

Answer 8

Stabilize eyes when head moves

Question 9

VOR Pathway

Answer 9

Vestibular Afferents
Vestibular nuclear complex @ pontomedullary junction
Ascending branch of MLF
Abducens, Trochlear, Oculomotor nuclei
Periocular muscles
Dynamic gaze stabilization

Question 10

VOR
- how many neuron arc?

Answer 10

3

Question 11

VOR
- Produces compensatory eye movements in response to head movement when

Answer 11

Equal amplitude and speed
Opposite direction
Allow stable gaze during head movements
Deficits produce oscillopsia

Question 12

Oscillopsia

Answer 12

The illusion of an unstable visual world, often experienced as a delay in visual motion following a head motion

Question 13

Ocular rotation reaction
- Head tilt response

Answer 13

Eyes must counter-roll contralateral to head

Question 14

How long does it take for eyes to counter-roll contralateral to head?

Answer 14

Slow, takes about 3 secs

Question 15

Ocular rotation reaction
- Head tilt response

Answer 15

**Need clarification on slide 61 from professor

Question 16

Perception of Visual Motion
- Saccades

Answer 16

Fast refixation of eyes on multiple points

Question 17

Perception of Visual Motion
- Smooth Pursuit

Answer 17

Slow tracking eye movements that maintain the image on the fovea

Question 18

VOR

Answer 18

Maintains stable vision during head motion

Question 19

Smooth pursuit circuit

Answer 19

Frontal eye field and temporal eye field could be contributing

Question 20

Voluntary saccades circuit

Answer 20

Less impactful
Something wrong with brain processing–> one of the central brain regions

Question 21

Smooth pursuit and saccades
- deficits can be caused by lesions of the:

Answer 21

Parieto-occipital cortex
Frontal cortex
Pontine nuclei
Cerebellar vermis
Cerebellar flocculus
Lateral medulla

Question 22

What else can contribute to smooth pursuit deficit?

Answer 22

Age

Question 23

What is a red flag?

Answer 23

Deficits in saccades or smooth pursuit
- Refer to MD

Question 24

Canals and Otolith convert mechanical energy into?

Answer 24

Electrical energy

Question 25

Canals and Otolith are sensitive to?

Answer 25

Plane of motion Direction of motion Quality of motion

Question 26

3 main targets of vestibular afferent information include

Answer 26

Cerebellum (adaptive processing) CN III, IV, VI (for VOR) Vestibular nuclei on the contralateral side (push-pull relationship)

Question 27

What is VOR?

Answer 27

Allows gaze stability while head is in motion by providing an equal and opposite eye movements to the head movement

Question 28

When VOR is not working properly what happens?

Answer 28

Other visual systems attempt to make up the difference but fail to do so perfectly (saccades and smooth pursuit)