Term
| Why did the engineering model of the eye succeed? Why study saccades? |
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Definition
The eye is an inertialess marble!
We don't lift weights with our eyes, entirely contained in the brain, superior colliculus component, and an engineering model that is testable. |
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Term
| How do we know that the motor system can affect your perception? |
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Definition
| a paralyzed eye muscle can still create a visual perception of the visual field moving, even though it is not moving! |
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Term
| Describe the motor map of the superior colliculus. |
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Definition
It's a 2-d sheet of saccadic eye movements
Not 3-D because it can't accomodate 3-d rotations (they don't commute), so 2-d is easier |
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Term
| What are the eye muscles that control horizontal motions? |
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Definition
| Lateral and medial rectus |
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Term
| What are the eye muscles that control vertical motions? |
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Definition
| Superior and inferior rectus |
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Term
| What are the eye muscles that control rotational motions? |
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Definition
| Superior and inferior obliques |
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Term
| What are the goals of Saccadic eye movements? |
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Definition
| Stabilize image on the retina! |
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Term
| Describe the vestibulo-occulo reflex |
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Definition
| Fixate on a stable object, while moving your head. |
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Term
| Describe the smooth pursuit mechanism |
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Definition
your eyes track slowly to fixate on a moving object, but the velocity of your eyes will lag compared to the object.
Low-pass filter
Flies move too quickly to follow with smooth pursuit. |
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Term
| Describe the optokinetic nystagmus |
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Definition
When the whole world moves, your eyes reach the end of their range of motion, and saccade back to the center.
The merry go round effect.
Vestibular damage will impair its function. |
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Term
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Definition
Keeps your eyes focused, even though they move in different directions (going cross eyed)
Controls the pupil, lens, and eye muscles. |
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Term
| Describe characterstics of a saccade when the head is restrained. |
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Definition
Velocity-Amplitude relationship is not linear.
Gaussian velocity profile, but skewed on the deceleration side
Abducens control the eye muscles |
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Term
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Definition
Eyes move together to focus on an object
High velocity conjugate movement
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Term
| What nucleus provides commands to the eye muscles? |
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Definition
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Term
| Why are there differences in saccades when the head is restrained versus when the head is moving? |
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Definition
| There are interaction effects between gaze, eye movements and head movements! |
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Term
| Describe the motor map in the superior colliculus |
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Definition
| Located in superficial layers, rostral to caudal axis (small->big amplitude), and medial to lateral (direction representation), coarsely tuned, generates desired displacement commands, NOT VELOCITY |
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Term
| What do omni-pause neurons do? |
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Definition
| Inhibit the activity of excitatory burst neurons, except when they are needed to generate the large impulse to start a saccade. |
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Term
| What do excitatory burst neurons do? |
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Definition
| Provide the initial impulse to get a saccade going to overcome viscosity. They integrate action potentials |
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Term
| What are the neural requirements for producing saccades? |
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Definition
1. Pulse proportional to saccade velocity
2. Step proportional to saccade amplitude |
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Term
| Describe why the inactivation experiment led to the view that the population of neurons responsible for coding saccades uses population averaging rather than vector summation. |
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Definition
| When half of the neural population was inactivated, the authors did not see and hypometric saccades. If the population was using vector summation, the inactivation would have removed half of the signal, thus decreasing the amplitude and velocity of the resultant saccades, so this model is very unlikely after this experiment. |
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Term
| What are the robinson commandments? |
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Definition
Electrical stimulation in the SC evokes Fixed Vector Saccades
Saccades do not depend on eye position
Saccades do not depend on stimulation parameters (all or nothing) |
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