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Vision Science 5 > Lecture 11 > Flashcards

Lecture 11 Flashcards

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1
Q

what are the 2 systems needed for clear and stable vision?

A

eye movement system (stabilize image on fovea) and accommodative system (clear image)

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2
Q

what is a saccadic eye movement?

A

brings the image of an object of interest rapidly onto the fovea

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3
Q

what is a smooth pursuit eye movement?

A

holds the image of a small moving target on the fovea

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4
Q

what is a vergence eye movement?

A

moves the eyes in an opposite direction so that images of a single object are held simultaneously on both fovea

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5
Q

what are 3 eye movements that direct the fovea to an object of interest?

A

saccades, smooth pursuits and vergences

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6
Q

what are 3 eye movements that hold images steady on the retina?

A

fixation, vestibular (VOR) and optokinetic

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7
Q

what is a fixation eye movement?

A

holds the image of a stationary object on the fovea when head is immobile

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8
Q

what is a vestibular (VOR) eye movement?

A

holds the image steady on the retina during brief head movements

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9
Q

what is an optokinetic eye movement?

A

holds image steady on the retina during sustained head movements or when the environment moves around the head

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10
Q

what are monocular eye movements called?

A

ductions

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11
Q

what are versions?

A

conjugate eye movements - 2 eyes move in the same direction by the same amount

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12
Q

what are vergences?

A

disjugate eye movements - 2 eyes move in opposite directions

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13
Q

what are the movements called for ductions in the z, y, and x-axis?

A 
z = abduction and adduction
y = elevation (supraduction) and depression (infraduction)
x = incyclotorsion and excyclotorsion
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14
Q

what are the movements called for versions in the z, y and x-axis?

A 
z = dextroversion and levoversion
y = elevation and depression
x = dextrocycloversion and levocycloversion
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15
Q

what are 4 types of version movements (conjugate)?

A

saccadic movement, smooth pursuit, vestibular (VOR) movement and optokinetic movement

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16
Q

what do conjugate eye movements control?

A

gaze control

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17
Q

what do disjugate eye movements control?

A

vergence control

18
Q

what is the input to the frontal eye fields (FEF)? what is the output?

A 
input = many cortical and subcortical areas 
output = superior colliculus and other gaze centers
19
Q

what is the function of the frontal eye fields (FEF)?

A

voluntary eye movements (not guided by target) and scanning the visual field

20
Q

where are the frontal eye fields located?

A

frontal lobe of cerebral cortex (brodmann’s area 8)

21
Q

where is the superior colliculus (SC) located?

A

pair of nuclei located on the upper surface of the midbrain

22
Q

what is the input to the superior colliculus (SC)?

A

retina, auditory system, somatosensory system and frontal eye fields

23
Q

what is the output from the superior colliculus (SC)?

A

to other gaze control centers

24
Q

what is the function of the superior colliculus (SC)?

A

controls the direction and magnitude of saccades

25
Q

where is the horizontal gaze center (PPRF) located?

A

located in the reticular formation of the pons (known as the Paramedian Pontine Reticular Formation)

26
Q

what is the input to the PPRF?

A

directly from the superior colliculus, FEF or cerebellum

27
Q

what is the output from the PPRF?

A

to nuclei of motor nerves controlling horizontal eye movements (directly or crossing midline via MLF)

28
Q

where is the vertical gaze center NIC located?

A

in the rostral part of the midbrain reticular formation (Interstitial Nucleus of Cajal)

29
Q

what is the output from the NIC?

A

to nuclei of motor nerves controlling vertical eye movements (CN3 and CN4)

30
Q

what is the medial longitudinal fasciculus (MLF)?

A

a midline tract in the medial midbrain and pons - connects the nuclei of the 3 eye movement motor nuclei

31
Q

what is the input or stimulus for a saccade?

A

target position, angle in degrees

32
Q

what is the input or stimulus for a pursuit?

A

target motion deg/sec

33
Q

what is the input or stimulus for a vergence?

A

vergence stimulation from disparity

34
Q

what is the input or stimulus for accommodation?

A

target distance in diopters

35
Q

what is the input or stimulus for VOR/OKN?

A

target velocity and head velocity

36
Q

what is the output in accommodation?

A

change in focus

37
Q

what is the output in a saccade?

A

change in angle of the eye/position

38
Q

what is the output in a pursuit?

A

change in velocity of the eye

39
Q

what is the output in a vergence?

A

change in position of the eyes

40
Q

what is the output in VOR/OKN?

A

change in velocity of the eyes

41
Q

how does an open loop system work?

A

none of the output is fed back into the input (no fine-tuning of the response)

42
Q

how does a closed loop system work?

A

all or part of the output is fed back into the input altering the final output

Vision Science 5 (14 decks)

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