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18 Cards in this Set
- Front
- Back
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What are saccades?
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Very rapid, conjugate eye movements as the eyes are targeting an "object".
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What area of the brain drives voluntary saccades?
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Frontal eye field of the cerebral cortex drives voluntary movements.
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What area of the brain collects three inputs and drives non-voluntary saccades. What are the three inputs to it?
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Superior colliculus drives reflex movements in response to signals from the retina, somatosensory system, and auditory system.
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What is the center for lateral gaze?
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PPRF (parapontine reticular formation) located in the pons region.
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What is the circuit for a saccade - voluntary left lateral gaze?
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Right frontal eye field -> Left superior colliculus -> left pprf -> left CN VI (to its muscle) -> MLF -> CN III (to its muscle)
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What is the circuit for a saccade - involuntary left lateral gaze?
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Right Visual signal from retina OR right auditory signal OR right somatosensory signal -> Left superior colliculus -> left pprf -> left CN VI (to its muscle) -> MLF -> CN III (to its muscle)
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What nucleus is involved in a saccade in vertical gaze?
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riMLF (rostral interstial nucleus of MLF)
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What is distinctive about the location of the horizontal gaze nucleus versus the vertical gaze nucleus?
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PPRF (Horz) in caudal pons. riMLF in midbrain and does not require circuitry caudal to it.
riMLF has some bi-lateral innervation of occular muscles and some ipsilateral. These pieces of info can help to sort out the location of a leison. |
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Describe smooth pursuit.
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The objective is to keep a moving target on the fovea ("targeting").
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Diagram the circuit for horizontal smooth pursuit to the right)
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Right Frontal eye fields and extrastriate cortex -> dorsolateral pontine nuclei -> left cerebellum (flocculus and posterior vermis) -> vestibular nucleus -> left VI (to its muscle) -> MLF -> right III (to its muscle)
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Describe vergence
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Vergence is a general term referring to the movement of convergence or divergence of the eyes.
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What cranial nerves mediate vergence?
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CN III
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What is the near response/near triad?
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Near response/near triad: eyes converge, pupils constrict, and the lens changes shape.
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Which cranial nerve(s) mediate each part of the near response?
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CN III
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Describe optokinetic movements.
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Optokinetic movements will consist of two parts: watching a moving, constant velocity object until to goes out of visual field, snapping the gaze to a new target.
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What is an example of an optokinetic movement?
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Watching train cars as a train passes. We might watch one car until it goes out of sight then switch to another car.
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How are optokinetic movements like vestibular Nystagmus?
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There is a slow phase (the smooth pursuit) alternating with a fast phase (saccade).
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How are optokinetic movements different than vestibular Nystagmus? Include a comment relating to acceleration and velocity.
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Optokinetic movements are driven by visual input rather than vestibular information (position of head), and this has a constant velocity versus acceleration in the vestibular case.
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