1. Eye Movements

2. 1. The Plant

3. The Oculomotor Plant Consists
Of only 6 muscles in 3 pairs

4. This Yields 3 degrees of
Mechanical Freedom

5. Donder’s Law/ Listing’s Law
Neural Constraints
Reduce this to
2 degrees of freedom

6. 3-D eye movements Donder’s Law Listing’s law Listing’s plane
Relates torsion to eye position
Listing’s law
Torsion results from rotation of eye around perpendicular axis
Listing’s plane
Plane orthogonal to line of sight
Does not apply when head is free

7. Kinematics vs Dynamics In the Oculomotor System
Rotations about the
Center of Gravity
No Loads
No Inertia
Force = Position

8. Oculomotor muscles and nerves
Oculomotor nerve (III)
Medial rectus
Superior/Inferior recti
Inferior oblique
Trochlear nerve (IV)
Superior oblique
Abducens nerve (VI)
Lateral rectus
Medial longitudinal fasciculus

9. 2. The Behaviors Gaze Holding: VOR OKN Gaze Shifting: Saccades
Vergence
Smooth Pursuit

10. Classes of eye movements
Reflexive – gaze stabilization
VOR
Stabilize for head movements
Optokinetic
Stabilize for image motion
Voluntary – gaze shifting
Saccades
Acquire stationary target
Smooth pursuit
Acquire moving target
Vergence
Acquire target in depth

11. Gaze During Nystagmus

12. Saccades

14. 3-D Gaze Trajectory
Vergence

16. 2. The Motor Neurons

17. Force Patterns
Robinson’s Lollipop Experiments
Statics
Dynamics

18. Oculomotor Neurons
During Static Gaze

19. Dynamics and Statics

21. 3. VOR

27. Cupula and otoliths move sensory receptors
Cristae
Maculae

30. Angular Acceleration
Angular Velocity
Angular Position
Cupula Deflection

31. Canal afferents code velocity
Spontaneous activity allows for bidirectional signaling
S-curve is common
Different cells have different ranges and different dynamics
Population code

32. Canal Output During
Slow Sinusoidal Rotation

33. VOR With and Without Vision

34. rVOR gain varies with frequency
Almost perfect > 1Hz
Low gain for low frequencies (0.1Hz)
Sensory mechanisms can compensate (optokinetic reflex)

36. Oculomotor muscles and nerves
Oculomotor nerve (III)
Medial rectus
Superior/Inferior recti
Inferior oblique
Trochlear nerve (IV)
Superior oblique
Abducens nerve (VI)
Lateral rectus

37. The 3-Neuron Arc Primary Effects of Canals on Eye Muscles
Canal Excites Inhibits
Horizontal Ipsi MR, Contra LR Ipsi LR, Contra MR
Anterior Ipsi SR, Contra IO Ipsi IR, Contra SO
Posterior Ipsi SO, Contra IR Ipsi IO, Contra SR

38. Robinson’s Model of the VOR

39. Robinson

40. 4. OKN

41. Type I Vestib Neuron

42. Bode Plot of OKN

44. Bode Plot of VOR

45. Bode Plot of OKN

46. 5. Saccades

51. Saccadic system

52. OPN Stimulation

53. Brainstem saccadic control
Paramedian pontine reticular formation (PPRF)
Burst and omnipause neurons
Aim to reduce horizontal motor error
Project to directly to lateral rectus motor neurons
Projects indirectly to contralateral medial rectus
Medial longitudinal fasciculus
Mesencephalic reticular formation
Also influenced by omnipause neurons
Vertical motor error
Projects to superior and inferior rectus motor neurons

57. Robinson’s Model of the VOR

59. Lee, Rohrer and Sparks

60. Jay and Sparks

63. 5. Pursuit

65. Smooth pursuit Track movement on part of retina Two theories
Motor (Robinson)
Retinal slip only provides velocity
Does not capture pursuit onset
Sensory (Lisberger and Krauzlis)
Position, velocity and acceleration

66. Smooth pursuit system

67. Smooth pursuit brainstem
Eye velocity for pursuit medial vestibular nucleus and nucleus prepositus hypoglossi
Project to abducens and oculomotor nuclei
Input from flocculus of cerebellum encodes velocity
PPRF also encodes velocity
Input from vermis of cerebellum encodes velocity
Dorsolateral pontine nucleus
Relays inputs from cortex to cerebellum and oculomotor brainstem

68. Smooth pursuit cortex Visual motion areas MT and MST
Active in visual processing for pursuit
Stimulation influences pursuit speed
Projects to DLPN and FEF
Does not initiate pursuit
Frontal eye fields
Stimulation initiates pursuit
Lesions diminish pursuit

73. Jergens

74. Scudder