visual motor systems Flashcards
frontal eye field is a
PRE-MOTOR area, and is brodman areas 6 and 8 (depends on textbook)
frontal eye fields receive target location from__ and project to___
- visual association cortex
- project to horizontal and vertical gaze centers of superior colliculus
3 types of eye movemtnts that direct targets to the fovea?
- SACCADES=> rapid mvmt toward new targets (conjugate)
- SMOOTH PURSUIT=>slower mvmts that follow moving targets (conjugate)
- VERGENCE=> mvmts that adjust the eyes toward near and far objects (disconjugate)
vestibulo-ocular reflex fxn
compensate for ACCELLERATION
aka–to keep things on your fovea –“foveation”
optokinetic reflex fxn
compensates for mvmt of the entire visual field
aka–holds images STEADY during sustained head rotation
pupillary light reflex fxn
maintains retinal illumination (4 neuron chain with ciliary ganglion and SHORT ciliary nerves)
blink reflex fxn
protects the eye
M1 (area 4)
random mvmts
SM (area 6)
planned mvmts
nuclei in the pons that have to do with visual system
- PPRF,
- abducens,
- MLF
nuclei in the midbrain that have to do with the visual system
- MLF,
- occulomotor nucleus,
- trochlear nucleus,
- nuclei of Cajal and riMLF (vertical eye mvmts)
two kinds of eye movement pathways
- nuclear and infranuclear pathways ==> brainstem nuclei and peripheral parts of CNIII, IV, VI
- supranuclear pathways ==> brainstem and forebrain circuits
what are frontal eye fields for in eye movements
- remembered movements,
- scanning for areas of interest
- suppressing uninteresting things
superior colliculus involvement in eye movements
- reflexive ORIENTATING. this spot has a map of your visual field so that if you see something interesting, your eye can accurately direct the fovea to that location
what are the only two muscles that do NOT pull the eye at a WEIRD angle
- lateral rectus
- medial rectus
what muscles and CN do you use for STRAIGHT and UPWARD gaze
- superior oblique (CN IV)
- superior rectus (CN III)
Hering’s law
during conjugate eye mvmts, the YOKED muscle pair receives EQUAL innervation so the eyes move TOGETHER
course of CNIII
- lateral wall of cavernous sinus (topmost nerve)
- receives nn from carotid plexus and V1
- enters s. orbital fissure THRU annulus
- DIVIDES to sup. and inf.
course of CNIV
- lateral wall of cavernous sinus below CNIII
- crosses III, enters s. orbital fissure THRU annulus
- has communications with CAVERNOUS plexus and V1
course of abducens nerve
- WITHIN cavernous sinus, lateral and inferior to ICA
- enters s. orbital fissure THRU annulus
- has communications with CAVERNOUS plexus and V1
horizontal gaze center
frontal eye fields and superior colliculus.
BUT. thats NOT the only function of these two things. they can do all the mvmts
three kinds of neurons in PPRF
excitatory burst => to abducens nucleus
inhibitory burst => to other abducens nucleus
omnipause neurons => allow your eyes to pause
visual deficit if you have demeylination in ventral pons
ipsilateral abducens nerve palsy
superior tarsal muscle
Innervation?
syndrome?
sypathetic fibers
horners syndrome. if the lesion is in the spinal cord or the superiro cervical ganglion, its full blown. if its after the ganglion, you ususally don’t have anhydrosis
internuclear neurons
for CONJUGATE eye movement for MLF
lesion of R abducens NERVE
R abducens nerve palsy. (ONLY R eye can’t look R)
lesion of R abducens NUCLEAR lesion
R lateral gaze palsy (the nucleus projects to TWO places, so NEITHER eye can go R)
lesion of R PPRF
PPRF is abducens nucleus. R lateral gaze palsy
lesion of L MLF
L internuclear ophthalmoplegia (can look L, but when you look R, the R eye gets nystagmus, and L eye can’t do it)
affects VI and contralateral III
lesion of L MLF plus the L abducens nucleus
you wipe out 1 and a half eye movements. “one and a half syndrome” (you can only look R in the R eye, but you get nystagmus in it)
vertical gaze centers
midbrain, close to occulomotor nucleus (riMLF and Cajal)
what parts of cerebellum are involved in these eye movements
fastigial nucleus, flocculus
if you have a pineal tumor, it presses on DORSAL MIDBRAIN. what will you see? (haha or not see)
- impaired vertical gaze
- large irregular pupils that don’t respond to light
- eyelid abnormalities
- impaired convergence
frontal eye fields project to?
- horizontal gaze center,
- superior colliculus
- vertical gaze center
superior colliculus UPPER layer info
input from the visual system for visual space
aka “WHERE is the info coming from”
superior colliculus LOWER layers
receive info FROM upper layers. the lower part does the MOTOR movements, and project to GAZE centers
smooth pursuit firing pattern?
its GRADED. aka you do NOT have bursts. its GRADUAL
smooth pursuit input from?
CBellum more than superior colliculus
**remember that vestibuloCBellum goes thru juxtarestofirm body to vestibular nuclei and then to the motor nuclei
NEAR response triad?
- eyes CONVERGE via action of medial recti
- lens ROUNDS UP increasing refractive power
- pupil CONSTRICTS (meiosis)
where does VERGENCE come from
MIDBRAIN!!!
- supraoculomotor area (SOA)
- not well known, but it obviously has to involve CNIII
occulomotor channel
supplementary eye fields
- VA,
- MD
lesion of parietal cortex affecting vision
related to SPATIAL information
- problems with where stream… SUPRAMARGINAL and ANGULAR gyri
- problems with saccades
- problems reaching for things in space
- “Simultagnosia” problems multitasking eye objects
what do NBME exams like to do
put in stupid charts of nerve impulses for things like nystgmus
always remember what about nystagmus
ALWAYS named for the FAST phase
