The superior rectus is and is supplied by
it is the muscle on the superior part of the eye moves the eye upwards
It is supplied by Cranial Nerve III, which is ipsilateral and the cell body is in the oculomotor nucleus in the midbrain (also connected to the inferior oblique, medial rectus, and inferior rectus)
the inferior rectus is and is supplied by
it is the muscle of the inferior part of the eye that moves the eye downward
it is supplied by CNIII, which is ipsilateral and who’s cell body is in the oculomotor nucleus, in the midbrain (also connected to the inferior rectus, interior oblique, medial rectus)
The medial rectus is and is supplied by
muscle that moves the eyes in towards the nose
It is supplied by cranial nerve III, which is ipsilateral, and who’s nucleus is in the oculomotor nerve of the midbrain (also supplies the superior rectus, inferior oblique, and inferior rectus)
the inferior oblique is and is supplied by
the muscle that moves the eye up and to the right / left
It is supplied by CNIII, who’s cell body is in the oculomotor nerve in the midbrain (also connects to superior rectus, medial rectus, and inferior rectus)
the superior oblique is and is supplied by
moves the eye down and to the left / right
it is controlled by CN IV, which is the only CN to be contralateral, but it crosses at the caudal midbrain, and its cell body is in the trochlear nucleus (caudal midbrain)
*truth be told…i’m actually contralateral
the lateral rectus controls and is supplied by
moves the eye outwards (opposite medial rectus)
CN VI, ipsilateral, cell body in the pons at the abducens nucleus
CN III
in addition to ocular-muscular activities, CNIII carries axons controlling muscles in the eyelid and the pupillary dilation reflex
saccade, with an example
quick, ballistic snap to a stimuli (ex. reading a book, eyes flipping to next line)
smooth pursuit and example
actively tracking movement to keep in fovea (ex. tracking a tennis ball moving across the court)
optokinetic response and example
puts saccades and smooth pursuit together, initial saccade then smooth pursuit to keep in line of sight (ex. watching telephone poles as you drive past them, saccade to get it in gaze, then smooth pursuit to keep it there until snapping to a new one)
for movements with greater gain than VOR
optokinetic nystagmus and example
visible back and forth pattern in the eyes produced by optokinetic response (behavioral eye movement resulting from OKR)
(ex. eyes snap to look at pole, slowly track pole, then snap to right to track a new pole)
vestibulo-ocular reflex (VOR) and example
eye movements to stabilize gaze when head moves
(ex. nodding your head yes while keeping eyes fixated)
for movement with greater gain than OKR
horizontal gaze center
paramedial pontine reticular formation (PPRF) located in the caudal division of the pons
(to move the eyes left)
It is a neuron with a cell body in the PPRF and interneurons connecting to the L abducens nucleus that connects ipsilaterally to the CNVI controlling the lateral rectus, and synapsing the medial longitudinal fasciculus which travels contralaterally to the right oculomotor nerve in the midbrain which syanpses CNIII controlling the R medial rectus muscle
vertical gaze center
rostral interstitial nucleus located in the medulla
it synapses via an interneuron on the oculomotor nerve which synapses the R and L superior and inferior rectus
gaze centers coordinate opposite inhibition
send circuit neurons to opposite abducens nucleus / oculomotor nucleus to inhibit opposite movement
what dictates amplitude (how far) of an eye movement?
the length of time of a.p.’s
What input goes to UMNs to gaze centers, controlling saccadic adjustment to salient stimuli?
Superior Colliculus (at most superior division of brainstem):
- visual layer receives input from retina
- sends into to motor layer which is organized based on motor intention / motor error (not visually organized bc study where animals should have exhibited motor error bc different starting point but they didn’t)
- which then sends info to contralateral gaze center
Frontal Eye Field (in premotor cortex):
- projects to SC to choose specific populations
Lesions in FEF
- saccadic response to stimuli eventually compensated by SC
- but make it challenging to move eyes away from stimuli
- hard to identify where a stimulus was that’s no longer visible
what can cause an active looking away from a salient stimuli?
basal ganglia activity
cerebellum can increase gain if needed of saccade
how does the brain control smooth pursuit?
involvement of cerebellum loop and extrastriate visual areas (e.g., MT, V2, V4) projecting to gaze centers
how does brain control vergence?
extra striate visual pathways project to vergence centers which project to the gaze centers
SCZ
Impairs smooth pursuit, sluggish initiation
