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71 Cards in this Set

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Visual input from each eye is transmitted independently through the __________ to the __________, where vision is perceived.
Lateral Geniculate Nucleus

Ocular Dominance Columns in Area 17
What muscles cause adduction of eye?
Middle Rectus
Superior Rectus
Inferior Rectus
What muscles cause abduction of eye?
Lateral Rectus
Superior Oblique
Inferior Oblique
What muscles cause elevation of eye?
Superior rectus
Inferior oblique
What muscles cause depression of eye?
Superior oblique
Inferior rectus
What muscles cause intorsion of eye?
Superior rectus
Superior oblique
What muscles cause extorsion of eye?
Inferior rectus
Inferior oblique
Abducting eyes will allow isolation of what muscles?
Superior Rectus
Inferior Rectus
Adducting eyes will allow isolation of what muscles?
Superior Oblique
Inferior Oblique
T/F - Corticobulbar fibers are directly received by the Occulomotor system (CN III, IV, VI)
False.

Though most CN's motor nuclei are excited by corticobulbar fibers (allowing for coritcal control), these are not.
For control of eye movements, where must the corticobulbar fibers project to?
Brainstem centers in the Reticular Formation
Define Gaze Center
Areas of Reticular Formation that program eye movements.
Where is the lateral gaze center (or PPRF or parabducens) located?
In RF at level of facial colliculus.
Where does the lateral gaze center (or PPRF or parabducens) project to in terms of muscle nuclei?
Ipsilateral abducens nucleus

Contralateral occulomotor nucleus
Describe the pathway for the lateral gaze center (PPRF or parabducens) to reach the eye muscles.
The center projects to the ipsilateral lateral rectus muscle. It also sends projections which decussates via MLF (medial longitudinal fasciculus) to the contralateral medial rectus muscles.
Where is the vertical gaze center (aka rostral intersitial nucleus of the MLF) located?
In RF at the level of superior colliculi.
Where does the vertical gaze center (aka rostral interstitial nucleus of the MLF) project to in terms of muscle nuclei?
Oculomotor nuclei

Trochlear nuclei
What brainstem center is responsible for convergence and divergence?
Perlia's nucleus
Perlia's nucleus is part of what complex?
Oculomotor complex
T/F - Perlia's nucleus utilizes the Medial Longitudinal Fasciculus in vergence movements.
False.
What are the two cells that brainstems of eye movements contain?
Burst cells

Tonic cells
Describe burst cells.
Extremely rapid firing cells that mediate saccadic (rapid) eye movements
Describe tonic cells.
Slower firing than burst cells that mediate slow movements
When eyes are stationary, describe the firing of burst and tonic cells.
Fire with constant rate
What does the nucleus prepositus hypoglossi do?
Integrate signals of saccadic eye movements to derive a new position signal for tonic cells.
What does the Oculomotor channel through the basal ganglia do?
Facilitate or suppress eye movements.
Where are GABA neurons located and what do they do?
In the Substantia Nigra pars reticulata

Exert inhibitory effect on eye movements, which ceases firing during saccades.
Where do the GABA neurons project to?
VA & VL Thalamus

Superior Colliculus
Basal Ganglia diseases can produce what symptoms?
Abnormal eye movement or eye fixation
List two Cerebral Cortical areas influencing eye movement.
Frontal Eye fields

Visual Association Cortex
Where are the Frontal Eye Fields located?
Brodmann's area 8 in the Middle Frontal Gyrus
What does the Frontal Eye Field do?
Directs Voluntary rotation of both eyes to contralateral side.

These are for saccadic eye movements
The Frontal Eye field receives input from where?
Visual Cortex
The Frontal Eye Field projects to where?
Contralateral Lateral Gaze Center

Vertical Gaze Center

Ipsilateral Superior Colliculus
Where is the visual association cortex located?
Brodmann's 18 & 19

Temporal Areas

Parietal Areas
Where does the visual association cortex receive input from?
Primary visual cortex
Where does the visual association cortex project to?
Contralateral Lateral Gaze Center

Vertical Gaze Center

Ipsilateral Superior colliculus
What does the visual association center do?
Directs smooth pursuit (tracking) movements mainly to ipsilateral side.
What are the two type of eye movements?
Conjugate and dysconjugate
What are the four types of conjugate eye movements?
1. Volunteer
2. Smooth pursuit (tracking)
3. Vestibulo-ocular reflex
4. Visual, Auditory, and Somatosensory reflex
Describe the movement character of voluntary eye movement, and state the involvement of each cell type.
Saccadic

Rapid jerks mediated by burst cells

Holding each eye in new position mediated by tonic cells
The voluntary eye movement is directed by what?
Frontal Eye Fields,

each moving eyes to the contralateral side.
Explain the effect of visual input in voluntary eye movements.
Can be utilized or overridden
Smooth pursuit (tracking) movements are mediated by what circuit?
Cortical reflex circuit.
What are the components of the cortical reflex circuit?
Visual association cortex

Temporal area

Parietal area
For smooth pursuit (tracking) movements of the eye, what signals are integrated?
Visual Association Cortex signal

Vestibular signal

Flocculonodular (cerebellar) signal.
The optokinetic reflex is induced how?
By movement of the whole visual field across retina (retinal slip)
Failure to elicit an optokinetic reflex may suggest what lesions?
Cortical lesion in areas 18, 19, temporal region, and parietal region.
What is an optokinetic reflex?
Ability to follow object across retinal field without moving head, then quickly "snap back" to another object in motion.
What is vestibulo-occular reflex?
Ability to move eyes opposite to head movement.

Thus eyes can remain fixed on object while head is moving
The vestibulo-ocular reflex results from stimulation of what?
Semicircular ducts
Clinically, the Vestibulo-ocular reflex is used to evaluate what in what type of patients.
Brainstem injury in unconscious patients.
Why would a unilateral legion cause vestibular nystagmus?
Since each gaze center receives BILATERAL, tonic input; a unilateral legion would cause an inbalance affecting the vestibulo-ocular reflex.
The visual, auditory, and somatosensory reflex have what kind of eye movements?
Saccadic
The visual, auditory, & somatosensory reflex involves what type of reflex circuit?
Strictly a subcortical (brainstem) reflex circuit.

Thus does not involve the cortex
The accomodation-convergence reflex is good for what?
Near vision
What happens in accomodation-convergence reflex?
Convergence - eyes rotate medially.

Accomodation - eyes focus for near vision

Miosis - pupils constrict for increased depth of focus
Each component of the accomodation-convergence reflex is mediated by what nerve?
Occulomotor nerve
What are the symptoms associated with a lesion on the oculomotor nerve? x4
1. External Strasbismus (exotropia) and Diplopia

2. Ptosis (more so than Horner's)

3. Midriasis (and loss of pupilary light reflex)

4. Loss of accomodation-convergence reflex
What are the symptoms of a lesion on the superior division of the oculomotor nerve?
Double elevator palsy
What are the symptoms associated with trochlear nerve lesions? x3
1. Hypertropia

2. Extortion

3. Vertical diplopia
What are the symptoms associated with abducens nerve lesions? x2
Internal Strabismus

Diplopia
What are the symptoms associated with lesion on abducens nuclei? x2
Same as lesion on abducens nerve PLUS lateral gaze paralysis
A lesion of the MLF would manifest what symptoms? x3
1. Internuclear ophthalmoplegia

2. No voluntary adduction

3. Nystagmus in the abducting eye.
Parinaud's syndrome would indicate a lesion where?
Midbrain Reticular Formation
Parinaud's syndrome would manifest what symptoms?
1. Paralysis of upward gaze

2. Mydriasis (and loss of pupillary light reflex)

3. Inpaired convergence
An irritative lesion of the frontal eye fields would manifest as what symptom?
Deviation of the eye to opposite side.
A destructive lesion of the frontal eye field would manifest as what symptom?
Deviation of the eye to side of lesion

Inability to gaze to opposite size
A lesion of the visual association cortex would manifest as what?
Defective tracking and convergence.
A vestibular nuclei lesion would manifest as what?
Nystagmus
A flocculonodular lobe lesion would manifest as what?
Nystagmus