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Visual Science: Ocular Motility > Ocular Motility: Lecture 8: Saccadic Eye Movements 2 > Flashcards

Ocular Motility: Lecture 8: Saccadic Eye Movements 2 Flashcards

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1
Q

Cerebral Control of Saccades

  1. What areas of the brain participate in the Control of SACCADES?
A
  1. FEFsac (saccade subregion of the frontal eye field), Supplementary Eye Field, and Dorsolateral Prefrontal Cortex, Parietal Eye Field (PEF), and Area 7a in Parietal Cortex
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2
Q

Control of Saccades

  1. What does the FEFsac do?
    a. What does it Project to?
  2. What does the PEF do?
    a. What does it project to?
A
  1. Starts VOLITIONAL and Visually Guided (Reflexive) Saccades
    a. to Superior Colliculus Directly and Via the PEF
  2. Starts VISUALLY GUIDED (Reflexive) Saccades
    a. IPSILATERAL SUPERIOR COLLICULUS and to the FEF
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3
Q

Cerebral Control of Saccades

  1. What else does the FEFsac project to?
    a. What does this do?
  2. What does the Substantia Nigra Pars Reticulata (SNpr) do?
    a. When does it TONICALLY DISCHARGE?
    b. What does it do when it PAUSES?
A
  1. CAUDATE NUCLEUS
    a. Sends INHIBITORY PROJECTIONS to the SNpr
  2. Sends Inhibitory Projections to the SUPERIOR COLLICULUS.
    a. During FIXATION
    b. DISINHIBITS the SC, which discharges before and during Voluntary and Visually Evoked Saccades
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4
Q

Cerebral Control of Saccades

  1. What does the CEREBELLUM Regulate?
    a. What does it Participate in?
A
  1. SIZE of SACCADES (dorsal oculomotor vermis and Fastigial Nucleus)
    a. in the REPAIR of SACCADE INACCURACY (Flocculus and Paraflocculus)
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5
Q

Cerebral Control of Saccades

  1. Dorsal Oculomotor Vermis
    a. What Lobules does it consist of?
    b. Receives Saccadic INPUT from what?
    c. When does it DISCHARGE?
  2. What does the NUCLEUS RETICULARIS TEGMENTI PONTIS do?
    a. What is this important in the CONTROL of?
A
  1. a. 6 and 7
    b. Nucleus Reticularis Tegminti Pontis
    c. BEFORE SACCADES
  2. Sends Inhibitory Projections to an ELLIPSOIDAL REGION in the CAUDAL FASTIGIAL NUCLEUS (Fastigial Oculomotor Region)
    a. SACCADE ACCURACY and CONSISTENCY
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6
Q

Cerebral Control of Saccades

  1. Activation of the FEFsac and SC on 1 side GENERATES what?
  2. Simultaneous Activation of FEFsac on Both Sides or SC on Both sides Generates what 2 things?
A
  1. CONTRALATERAL HORIZONTAL SACCADES

2. VERTICAL and TORSIONAL SACCADES

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7
Q

Cerebral Control of Saccades

  1. Lesion Affecting BOTH FEFsac and SC?
  2. Lesion either FEFsac or SC?
  3. Lesion of the Dorsal Vermis?
  4. Lesion of the Fastigial Nucleus?
A
  1. DEFECTIVE SACCADE GENERATION
  2. Mildly Hypometric and Delayed (Increased Latency) Saccades
  3. Dysmetric and Slow Saccades
  4. DYSMETRIC and SLOW Saccades
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8
Q

Brainstem Control of Saccades: Excitatory (EBN)

  1. Medium-Lead EBN
    a. What do they turn on?
    b. Location for Horizontal Saccades?
    c. Location for Vertical and Torsional Saccades?
  2. Long-Lead EBN
    a. What do they turn on?
    b. Location?
A
  1. a. Moto-Neurons to AGONIST MUSCLES (fire 8-15 msec before and during Saccades)
    b. NRPC (nucleus reticularis pontis caudalis) which is w/in (Paramedian Pontine Reticular Formation)
    c. riMLF
  2. a. Medium-Lead EBM and INHIBIT Omnipause Neurons (100 msec before Saccade Onset)
    b. Rostral PPRF, and Mesencephalic Reticular Formation
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9
Q

Brainstem Control of Saccades: Inhibitory (IBN)

  1. What do they do?
    a. Location for Horizontal Saccades?

b. For Vertical and Torsional Saccades?

A
  1. Inhibit Motoneurons to Antagonist Muscle (fires just before and During Sacades)
    a. PGD and PPRF
    b. riMLF
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10
Q

Brainstem Control of Saccades: Omnipause Neurons

  1. What do they do?
  2. Stop firing when?
  3. Location?
A
  1. Tonically Inhibit Burst Neurons
  2. 10-12 msec before and during saccades: Possibly via Inhibition from Long-Lead EBN
  3. rip w/in the PPRF
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11
Q

Model of Saccade Generation

  1. Saccades are initiated by TRIGGER SIGNALS from what 2 places?
    a. What do they inhibit?
  2. What does this inhibition do?
  3. What determines how long the Burst Neurons FIRE?
    a. Duration of their firing determines what?
  4. The Medium-Lead Excitatory Burst Neurons Generate an Eye Velocity Command (the Pulse), which is Integrated to create what?
A
  1. From the Cerebral Hemispheres and Superior Colliculi
    a. Omnipause Neurons
  2. Lets Excitatory Burst Neurons to Discharge
  3. a Desired eye Position Signal (retinal target error)…which is independent of the Trigger Signal
    a. the Amplitude of Saccades
  4. a New Position Command (the Step) by the Velocity-to-position Neural Integrator
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12
Q

Model of Saccade Generation

  1. Pulse-Step of Innervation is Sent to what?
    a. What does this do?
  2. Collaterals of Medium-Lead Excitatory Burst Neurons also Activate what Neurons?
    a. These Inhibit what 2 things during the Saccade?
  3. Once the Actual Eye Position Matches the Desired Eye Position, what do the Burst neurons do?
    a. What about the Omnipause cells?
A
  1. to the Motoneurons
    a. Moves and Maintains the Eye in a New Position
  2. Inhibitory Burst Neurons
    a. Antagonist Motoneurons and Omnipause Neurons during the Saccade
  3. they STOP FIRING
    a. They RESUME their TONIC ACTIVITY, and the SACCADE STOPS!
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13
Q

Horizontal Saccades

  1. EBNs in PPRF send signals to what neurons?
    a. This generates a Saccadic Pulse to move what?
  2. Abducens Internuclear Neurons in the Abducens Nucleus, Send Axons to what?
    a. Via what?
    b. What happens next?
  3. What does the Neural Integrator (Nucleus Prepositus Hypoglossi-Medial Vestibular Nucleus (NPG-MVN)) do?
  4. What do the Omnipause Neurons in the NUCLEUS RAPHE INTERPOSITUS do?
A
  1. Abducens Motoneurons in the Abducens Nucleus
    a. to move the IPSILATERAL EYE RAPIDLY to a NEW POSITION
  2. to the CONTRALATERAL MEDIAL RECTUS Subnucleus
    a. Via the MLF

b. Medial Rectus Motoneurons generate a SACCDAIC PULSE to move the Fellow Eye RAPIDLY to a NEW POSITION (internuclear pathway also transmits VOR and Pursuit Eye Movement Signals to the Medial Rectus)
3. Generates a Saccadic Step to hold the Eyes in a New Position (Gaze HOLDING)
4. TONICALLY INHIBIT EBN in PPRF and in riMLF

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14
Q

Abnormal Saccades

  1. Lesion of the MLF CAUSES what?
    a. This is a CARDINAL MANIFESTATION of what?
  2. DISCRETE LESION of the PPRF causes what?
  3. Lesion of NPH-MVN causes what?
  4. Lesion of Nucleus Raphe Interpositus Causes what?
A
  1. ADDUCTION PALSY
    a. INTERNUCLEAR OPHTHALMOPLEGIA (Right MLF Lesion = Adduction palsy, affects adducting saccades, VOR and Pursuit of the right eye)
  2. CONJUGATE, Horizontal Saccadic Palsy to the Same Side (right PPRF lesion = conjugate saccadic palsy to the right)
  3. Horizontal Gazed-evoked Nystagmus due to failure of GAZE HOLDING
  4. SLOWING of SACCADES
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15
Q

Upward and Downward Saccades

  1. Right riMLF generates what?
  2. Left riMLF generates what?
A
  1. Conjugate Clockwise Saccades

2. Conjugate Counterclockwise Saccades ONLY

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16
Q

Upward Saccades

  1. EBNs generate a SACCADIC PULSE and Project via what?
    a. To what 2 things?
    b. Where do Axons cross?
    c. To Innervate what?
    d. EBNs also Send Collaterals to what? Which integrates what?
A
  1. the MLF
    a. Ipsilateral SR and IO Subnuclei of the Oculomotor Nucleus
    b. w/in the Oculomotor Nucleus
    c. The CONTRALATERAL SR and IO Subnuclei
    d. to INC BILATERALLY; Integrates the Pulse into a STEP command
17
Q

Downward Saccades

  1. EBNs Project via what?
    a. To what?
    b. Axons decussate to innervate what?
    c. EBNs also SEND COLLATERALS to what?; Which integrates what?
A
  1. the MLF
    a. the IPSILATERAL IR Subnucleus of the Oculomotor Nucleus and to the IPSILATERAL Trochlear Nucleus

b. the SO of the Opposite Eye
c. to IPSILATERAL INC; Integrates the Pulse into a STEP COMMAND

18
Q

Abnormal Saccades

  1. UNILATERAL LESION of riMLF causes what?
  2. Bilateral Lesion of riMLF causes what?
  3. Unilateral Lesion of INC (Leaky Integrator) Causes what?
A
  1. Slowing of Downward Saccades and Loss of Ipsitorsional Saccades
  2. Saccadic Palsy in ALL DIRECTIONS
  3. Torsional Nystagmus w/Ipsilesional Quick Phase (i.e., Upper Poles of BOTH Eyes Beat toward the Side of the Lesion)
19
Q

Abnormal Saccades

  1. Slowed Dynamics? (causes: 5)
  2. Inaccurate Amplitude (4)
  3. Delayed (2)?
A
  1. AIDS, Alzheimer’s, Parkinson’s, MS, Thyroid
  2. Amplitude, MS, Frontal and Parietal Lobe Lesions, and Parkinson’s
  3. Amblyopia; Alzheimer’s, Parkinson’s, MS
20
Q

Abnormal Saccades: Site of Lesion

  1. Motoneurons and Ocular Motor Nerves
  2. Premotor:
    a. PPRF
    b. RiMLF
  3. Omnipause Neurons
  4. Cerebellar Vermis (Bilateral)
  5. Cerebellar Fastigial Nucleus (Bilateral)
  6. SC
  7. Thalamus
  8. Parietal Eye Field
  9. Frontal Eye-Field
  10. Supplementary Eye Field (SEF) and pre-SEF
A
  1. Slowed Saccades, Limited range of movement
  2. Slow Saccades
    a. Horizontally
    b. Vertically and Torsionally
  3. Saccadic Oscillations; Slow horizontal and vertical saccades
  4. Saccadic Hypometria
  5. Saccadic Hypermetria
  6. Loss of Short-Latency (express) Saccades
  7. Inaccurate responses to double-step stimuli
  8. Increased Latency of Visually Guided Saccades; Inaccurate Responses to double-step stimuli; Impaired Visual Search
  9. Bilaterally increased Latency to Overlap stimuli, Remembered targets, and in Antisaccade task; Contralateral Hypometria to Visual or Remembered Targets
  10. Impaired ability to make a remembered sequence of saccades, and to reverse the direction of a previously established pattern of response
21
Q

Quick Phases

  1. Spin patient in a swivel chair to elicit what?
    a. Or use what to elicit OKN?
  2. Loss of Quick Phases is usually due to what?
A
  1. the VOR
    a. Optokinetic Drum
  2. LESION of the PREMOTOR BURST NEURONS in the Brainstem
22
Q
  1. Defects of Predictive Saccadic control are common in what?
  2. Loss of Voluntary Saccades w/preservation of quick phases and visually guided (reflexive) saccades is characteristic of what?
A
  1. Parkinson’s Disease

2. of ACQUIRED OCULAR MOTOR APRAXIA

Visual Science: Ocular Motility (14 decks)

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