Control of Eye Movements Flashcards
What parts of the brain achieve control of eye position?
medial longitudinal fasciculus
reflexes
cerebral centers
What is saccadic movement?
rapid eye movement that brings image of object onto the fovea
What is smooth pursuit?
keeps a moving image centered on the fovea
What is vestibular-ocular gaze control?
holds image steady on the fovea during head movements
What is vergence?
keeps image on fovea when object is moved near
(crossed-eyed)
What is optokinetic gaze control?
doing smooth pursuit and moving your head
holds the image steady on the retina during sustained head rotation
visual target is broken whn the target reaches the limit of the visual field –> eyes make a quick move in opposite direction
What are the 5 supranuclear gaze control systems?
saccadic
smooth pursuit
vestibular-ocular
vergence
optokinetic
(all are conjugate movements except vergence)
How do you look at a face?
tend to focus on eyes, nose, and mouth
saccadic movement jumps around to those areas
your brain doesn’t notice the saccades
If your right frontal eye field sends info to the PPRF, which way are your eyes going to turn?
left
What is the saccadic horizontal system?
frontal eye fields and superior colliculus –> PPRF –> Nucleus 6 –> LR m and Nucleus 3 –> medial rectus m
What is the vertical saccidic system?
frontal eye fields and superior colliculus –> rostral interstitial nucleus of the medial long fasciculus (riMLF) –> CN 4 nucleus and CN 3 nucleus
How would a tumor in the pineal gland/ superior midbrain affect vision?
selective palsies of vertical gaze = can’t look up
How would tumors of the red nucleus affect vision?
have difficulty looking down
What parts of the brain contribute to reflex saccadic eye movements?
supplementary and parietal eye fields
soperior colliculus
What are the types of neurons used in saccades?
- burst of excitatory neurons to move eyes toward target
- tonic neuronal firing (tonic neurons) for final locking and fixing of gaze
- pause neurons: inhibit burst neurons so no further mvts occur
Where are the burst, tonic, and pause cells in the horizontal saccadic system?
Burst: PPRF
Tonic: nucleus prepositus hypoglossi (pons)
Pause: omnipause cells of raphe nuclei
Where are the burst, tonic, and pause cells in the vertical saccadic system?
Burst: rostral interstitial nucleus of MLF (riMLF)
Tonic: interstitial nucleus of cajal (midbrain)
Pause: omnipause cells of Raphe nucleus
Where is the PPRF?
posterior pons
Where are the interstitial cells of cajal and what is there significance?
In the midbrain close to red nuclei
hold the tonic cells for the vertical saccadic system
(tumor of red nucleus –> affects ability to look down)
How do lesions of the frontal gaze center affect vision?
destructive lesion –> eyes deviation toward the side of the lesion (stare at train wreck)
sezure activity (irritative lesion) –> eyes deviate away from the area of irritation (look away from annoying thing)
What is the smooth pursuit tract?
(R brain signalled –> will look right)
parieto-occipital jxn –> pontine nuclei –> vestublar nuclei and vestibulocerebellum –>
horizontal: CN 6 and 3
vertical: CN 3 and 4
What is optokinetic nystagmus?
when your eyes are following a target during head motion w/ smooth pursuit
then the target reaches limit of visual field and you can’t see anymore –> eyes make quick move in the opposite direction
What parts of the brain are used in the optokinetic reflex?
Visual association cortex –> parietooccipital eye field –> nuclei of the accessory optic system and nucleus of the optic tract –> inferior olive, vestibular nuclei, and vestibulocerebellum –> CN nuclei –> muscles
