Control of Eye Movements Flashcards
What are the important players in terms of controlling eye position?
MLF (medial longitudinal fasciculus, reflexes and cerebral centers)
What is saccadic movement? How about smooth pursuit?
Chopped up focus/rapid eye movements trying to focus an image on the fovea (scanning the room)
Smooth pursuit keeps a moving image centered on the fovea when head isn’t moving
What is vestibulo-ocular eye movement? How about vergence?
Holds image steady on fovea while head is moving
Keeps image steady on fovea when trying to see near and far
What is optokinetic eye movement?
keep image on retina while following a target
What are the major players involved in saccadic movement?
Frontal eye field (voluntary) and superior colliculus (reflexive)
What is the relay center for horizontal saccades and which part of the brainstem is it located? Which CNs are important for this?
What about vertical saccades?
Contralateral paramedian pontine reticular formation (PPRF/horizontal gaze center) in pons. CN III and VI
Rostral interstitial nucleus of the MLF (riMLF)/vertical gaze center in midbrain. CN IV and VI
Draw the pathway for horizontal saccades
Ok
Which frontal eye field and PPRF are active when eyes are turning left?
Lesion in the PPRF results in?
Right frontal eye field and left PPRF (and vice versa)
Both eyes cannot look to the side of the lesion
What happens when you have a pineal tumor?
Compression of the superior colliculus and posterior commissure = problems with vertical saccades
Damage to the nucleus of Cajal and red nucleus results in?
Problems with downward saccades since the circuit passes through this general area (medial midbrain)
What are the major players involved for reflexive saccades?
Supplementary and parietal eye fields and superior colliculus
Explain the mechanism for enabling saccadic control
Excitatory burst that moves eye towards the target > tonic neuron firing which locks the target on the fovea > pause neurons to hold the image still
What are the burst, tonic and pause cells for horizontal saccades?
Burst: PPRF
Tonic: Nucleus prepositus hypoglossi
Pause: omnipause cells of Raphe nuclei
What are the burst, tonic and pause cells for vertical saccades?
Burst: riMLF
Tonic: Interstitial nucleus of Cajal
Pause: Omnipause cells of raphe nuclei
How do you test saccadic movement?
Visually jump from one object to another