oculomotor and motor learning

Question 1

what is convergence?

Answer 1

when eyes come together in the center occurs together ( driven by something above the third nerve ( not the mlf)

Question 2

what is the only thing preserved in bilateral internuclear opthalmoplegia and why ?

Answer 2

convergence only CN II and III are used not CN VI

Question 3

what is internuclear opthalmoplegia and give a description of how it works?

Answer 3

disconjugate horizontal gaze due lesion of Medial longitudinal fasciculus (MLF) or Parapontine reticular formation ( PPRF)

ex. R. eye will not adduct when asked to look left voluntarily, but can move when
following a finger (CN VI is preserved)

Question 4

what is OKN, OptoKinetic Nystagmus?

Answer 4

the eyes can jump focus, ex. switching targets as we walk - also steadies the scene against movement

Question 5

what are saccades and what determines the rate of them?

Answer 5

Fast eye movements to shift the visual scene onto the fovea

- the forebrain decides where saccades should go ( when and where we look)

Question 6

Frontal Eye Field controls ?

Answer 6

voluntary eye movements

Question 7

Superior Parietal Cortex controls?

Answer 7

involuntary pursuit movements

Question 8

where is the vertical gaze center?

Answer 8

Vertical gaze center/saccade generator is in the midbrain ( nucleus of cajal)

Question 9

where is the horizontal gaze center?

Answer 9

Horizontal gaze center is in the PPRF

Question 10

what do vergence and Accomodation do?

Answer 10

adjust the plane of focus

Question 11

what is Oculomotor Apraxia?

Answer 11

lesion to frontal eye fields & loss of voluntary eye movements

can’t voluntarily move eyes e.g. can’t “look right” on command but can still follow a finger to the right

Question 12

what happens to the visual ocular reflex in oculomotor apraxia?

Answer 12

• Visual ocular reflex preserved. Patient often “exceeds target” as they turn their head to try and
  see an object in their periphery. Also will see them blinking to break the VOR
  and shift their gaze.

Question 13

what occurs in Left CN VI Palsy?

Answer 13

N VI damage

- the eye can’t move laterally, either voluntarily or involuntarily

Question 14

what is characteristic of Forebrain problems ?

Answer 14

symmetrical, conjugate problems.

Question 15

what is characteristic of nerve or nuclei problems?

Answer 15

disconjugate movements, diplopia

Question 16

how does the saccade generator work?

Answer 16

A saccade requires both a “burst” of firing to overcome inertia and initiate eye movement + a new “tonic” firing rate to maintain the new position ( see image on page 988)

there is a burst of activity and a new firing rate which is the integral of the speed of the burst activity

Question 17

what happens if the pause cells aren’t working?

Answer 17

opsoclonus: make random saccades , could be congenital and get better or could not be congenital

Question 18

what type of problems do you get when saccade generator isn’t working?

Answer 18

brainstem problems

Question 19

what hppens when there is a problem with burst cells?

Answer 19

slow saccades

Question 20

what happens when there is a problem with the integrator?

Answer 20

eye moves but can’t keep it there so it drifts back

Question 21

What types of info/ control does the cortex give/have to/on the saccade generator?

Answer 21

Motor Error: difference between current visual
field and where you want to look

Trigger: tells the eyes when to move (ex. pretty woman at the mall…)

Question 22

problems with what four things can cause diplopia?

Answer 22

mlf, burster cells, cranial nerves, cranial nuclei