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Flashcards in Eye Movements Deck (21):
1

What are the four types of eye movements?

1. smooth pursuit
2. saccades
3. reflexes
4. vergence

2

smooth pursuit

tracking
to keep an object on the fovea)

3

saccades

1. rapid, ballistic “jumps” to bring an object onto the fovea
2. There is suppression of visual information during a saccade
3. Why you don’t see a blur of the visual world during a saccade
4. Average of 3 saccades per minute during the day!

4

reflexes

1. neither is monosynaptic
2. VOR: Vestibular ocular reflex (vestibular system)
3. OKN: optokinetic nystagmus (visual object movement)

5

vergence

moving the fovea to an object closer (convergence) or farther away (divergence)

6

Conjugate eye movements:

1. both eyes move in the same direction.
2. Initiated by a variety of sensory inputs, visual and vestibular inputs most important

7

Vergence eye movements:

1. eyes movie in opposite directions
2. Example – both eyes turn nasally (“cross-eyed”) during the near reflex

8

Near reflex:

1. the combination of changes our eyes undergo when we attempt to focus on a near object.
2. Both medial recti contract, pulling the eyes nasally.
3. Pupils constrict to increase the depth of field
4. Ciliary muscles contract, allowing lens to become fatter and thus focus on a near object.

9

near reflex is driven by

visual input to association areas of the visual cortex

10

saccade is a

a rapid movement that brings the eyes to a predetermined target or position at a rate of up to 700˚/second

(contrast to smooth pursuit, which tops out at 50˚/second).

11

Saccades can be used to

1. restore the eye toward the center of orbit during some tracking tasks, whether it was visually or vestibularly evoked.

2. used in voluntary way to rapidly foveate an interesting peripheral stimulus, moving the eye away from the center of orbit.

12

Visually-evoked saccades are ballistic in character

1. Programmed to foveate a particular target, even if the target moves after the saccade is initiated.
2. A very high frequency burst is needed for initial acceleration
3. A carefully calculated steady rate is required to maintain the new eye position

13

Optokinetic nystagmus

Rhythmic pattern of saccades and tracking movements elicited by a simple stimulus like a rotating striped drum

14

Saccades control centers are in the ____

cortex and the superior colliculus.

15

Motor neurons and pattern generators for saccades are located in the ___

midbrain and pons.

16

Vertical saccades –

pattern generator located near the oculomotor nuclei (midbrain)

17

Horizontal saccades –

pattern generator located in the reticular formation near the abducens nucleus
(in the paramedian pontine reticular formation (PPRF))

18

motor neurons for vertical eye movements are in the _____, while motor neurons for horizontal eye movements involve the ______.

oculomotor nucleus

abducens nucleus

19

Horizontal saccades are driven ____

contralaterally

E.g. saccade to the left is driven by activity in the right frontal eye field.

20

The frontal eye field in the frontal lobes of the cortex can activate saccades by two pathways:

1. Direct to the reticular formation
2. Via the superior colliculus and then to the reticular formation

21

Activation of saccades via the superior colliculus has a:

1. retinotopic map AND
2. an auditory spatial map AND
3. a somatotopic map

that are ALL superimposed on a motor map for the movement resulting from the saccade.