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Vision Science 5 > Lecture 12 Objectives > Flashcards

Lecture 12 Objectives Flashcards

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1
Q

What is the saccadic hierarchy from low to high?

A 
Quick phases of VOR/OKN
Visually guided (reflexive saccades)
Volitional saccades (1-4)
1. to command
2. Predictive, anticipatory
3. Memory guided
4. Antisaccades
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2
Q

What are the five characteristics of saccades?

A 
Latency
Velocity
Duration
Amplitude
Accuracy
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3
Q

What is normal latency of saccades?

A

200msec, +-50

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4
Q

What things affect latency?

A

Patient motivation
Attention
Target predictability

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5
Q

What is the normal velocity range for saccades?

A

30-700 degrees per second

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6
Q

What is the max speed of saccades?

A

1000 degrees per second

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7
Q

Peak velocity of saccades increases with what?

A

Amplitude

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8
Q

What is the normal duration of saccades?

A

30-100msec

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9
Q

Duration of saccades increases with what?

A

Amplitude

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10
Q

Which two characteristics of saccades demonstrate a main sequence relationship?

A

Velocity

Duration

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11
Q

What is the normal amplitude for saccades?

A

Less than 15 degrees

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12
Q

Gaze changes larger than 15 degrees usually stimulate what?

A

Head movement as well as saccadic eye movement

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13
Q

How is accuracy of saccades described?

A

Hypometria

Hypermetria

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14
Q

When does hypometria tend to occur?

A

With large amplitude saccades

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15
Q

When does hypermetria tend to occur?

A

With small amplitude saccades

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16
Q

Hypometria is usually less than __% of the overall amplitude.

A

10%

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17
Q

If there is a lesion in the fastigial nuclei, what type of saccades will most likely be seen?

A

Hypermetric saccades

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18
Q

With age, what happens to saccadic latency?

A

Increases by 1-2msec per year

19
Q

With age, what happens to saccadic peak velocity?

A

Decreases by 1 degree per second, per year

20
Q

With age, what happens to saccadic gain and accuracy?

A

They don’t change with age

21
Q

What may reduce saccadic gain and accuracy?

A

Fatigue

22
Q

What is the saccadic pulse?

A

A phasic muscle contraction that moves the eye rapidly against the orbital tissues

23
Q

What is a saccadic step?

A

A tonic muscle contraction to hold the eye steady at its new position

24
Q

What determines saccadic velocity?

A

Pulse innervation - the higher frequency of firing causes faster movement

25
Q

What are the three important neurons in the saccadic pulse generator?

A

Motor neurons
Burst neurons
Omnipause neurons

26
Q

In saccades, where does the signal for horizontal movement begin?

A

Burst neurons in PPRF

27
Q

In saccades, where doe the signal for vertical movement begin?

A

Burst nurons in the riMLF

28
Q

Where are omnipause neurons located?

A

Raphe Interpositus (RIP)

29
Q

What inhibits both horizontal and vertical burst neurons?

A

Omnipause neurons

30
Q

What is the neural integrator (NI) for horizontal saccades?

A

Nucleus Prepositus Hypoglossi and Medial Vestibular Nucleus (NPH-MVN)

31
Q

Where is the NPH-MVN located?

A

Medulla

32
Q

What is the neural integrator (NI) for the vertical and torsional saccades?

A

Interstitial Nucleus of Cajal (INC)

33
Q

Where is the INC located?

A

Midbrain

34
Q

What is the effect of a lesion of the PPRF?

A

Slow or absent horizontal saccades to the same side

35
Q

What is the effect of a lesion of the riMLF?

A

Slow or absent vertical saccades

36
Q

What is the effect of a lesion of the RIP?

A

Disruption of omnipause neurons, leading to saccadic oscillation like opsoclonus and flutter
Slow saccades

37
Q

What is the effect of a lesion of the NPH-MVN?

A

Horizontal gaze-evoked nystagmus due to failure of gaze holding

38
Q

What calculates egocentric direction?

A

Posterior Parietal Cortex (PPC)

39
Q

What do the parietal eye fields (PEF) do?

A

Initiate reflexive, visually guided saccades

40
Q

What initiates voluntary saccades?

A

Frontal eye fields (FEF)

41
Q

What does the superior colliculus control?

A

Saccade trajectory

42
Q

What is the pathway of reflexive saccades?

A

V1
PEF
SC
Brainstem saccade generator

43
Q

What is the pathway of voluntary saccades?

A

V1
FEF
SC
Brainstem saccade generator

Vision Science 5 (8 decks)

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