Eye Movement Physiology
Frank M. Marchak, Ph.D.
Veridical Research and Design Corporation
www.vradc.com
Society for Psychophysiological Research
September 14 2011
Eye Anatomy
webvision.med.utah.edu/imageswv/Sagschem.jpeg
www.skybrary.aero/images/thumb/Vis_Fig2.jpg/500px-Vis_Fig2.jpg
Why do you move your eyes?
Yarbus (1967)
Task influences eye movement behavior
Types of Eye Movements
• Gaze Stabilization
– Vestibulo-ocular
– Optokinetic
• Gaze shifting
– Vergence
– Smooth Pursuit
– Saccade
Gaze Stabilization
Vestibulo-Ocular Reflex
commons.wikimedia.org/wiki/File:Vestibulo-ocular_reflex_lateroflexion
_of_neck.svg
www.youtube.com/user/mbolding#p/u/15/PeO6w_bCz8U
• Stabilize eyes relative to external world
- Compensate for head movements
Gaze Stabilization
Optokinetic Nystagmus
img.springerimages.com/Images/ImagesMD/ATOPH/01/66/WATER_ATOPH01-0966-003B.jpg
www.youtube.com/watch?v=KSJksSA6Q-A&feature=related
• Elicited by moving objects that produce illusion of
head movement or slow head movements
undetected by vestibular system
• Visual-ocular response
Gaze Shifting
Vergence
schorlab.berkeley.edu/vilis/vergence.htm
www.youtube.com/user/mbolding#p/u/16/9kgi_Avr66I
• Align fovea of each eye with targets at different
distances from observer
- Disconjugate
Gaze Shifting
Smooth Pursuit
Wetenbakerr,(1984). The Eye: Window on the World
• Keep moving stimulus on fovea
- Under voluntary control
www.youtube.com/watch?v=kEfz1fFjU78
Gaze Shifting
Saccadic
www.youtube.com/watch?v=FEJfAxJEP6E
• Ballistic movements that abruptly change point of fixation
How do you move your eyes?
Extraocular Muscles
eyeaerobics.com/program/
IO
SR
LR
MR
SO
IR
IO/SR
SR/IO
SO/IR
IR/SO
MR
MR
SR
IO
MR
LR
IR
SO
CONVERGENCE
emedicine.medscape.com/article/1189759-overview
Ophthalmotrope (Ruete, 1857)
bjo.bmj.com/content/93/5.cover-expansion
Extraocular Muscle Innervation
Extraocular Muscle Innervation
Origins
Extraocular Muscle Innervation
Ocular Motor Neuron Nuclei
Purves, et al., (2004). Neuroscience
Extraocular Muscle Innervation
Ocular Motor Neuron Nuclei
www.sharpsight.in/images/treatments/eye%20trackers.jpg
Saccadic Eye Movements
express.howstuffworks.com/gif/body-saccidic-composite.jpg
Time Course of Saccades
Purves, et al., (2004). Neuroscience
• Two components
• Amplitude
• Lower motor neurons within oculomotor nuclei
• Direction
• Premotor neurons in gaze centers in brainstem
Neural Control of Saccades
Purves, et al., (2004). Neuroscience
Purves, et al., (2004). Neuroscience
• Discharge frequency directly proportional to
position and velocity of eye
Neural Control of Saccades
Pulse-Step
• Pulse
- Tonic signal – eyes hold position
- Height: speed of saccade
- Duration: duration of saccade
• Step
- Phasic signal – eyes move
- Height: amplitude of saccade
brain.phgy.queensu.ca/pare/assets/Oculomotor%20lecture.pdf
Neural Control of Saccades
Gaze Centers
• Horizontal
- Paramedian pontine
reticular formation
(PPRF)
• Vertical
- Rostral interstitial
nucleus (rostral iMLF)
cueflash.com/decks/CONTROL_OF_EYE_MOVEMENTS_-_57
Neural Control of Saccades
Horizontal Eye Movements
Purves, et al., (2004). Neuroscience
Horizontal Saccades
Excitatory Burst Neurons
• PPRF
– Phasic signal of abducens
motor neurons
brain.phgy.queensu.ca/pare/assets/Oculomotor%20lecture.pdf
Horizontal Saccades
Tonic Neurons
• Nucleus prepositus
hypoglossi
– Tonic signal of abducens motor
neurons
brain.phgy.queensu.ca/pare/assets/Oculomotor%20lecture.pdf
Horizontal Saccades
Inhibitory Burst Neurons
• Paramedian pontine reticular
formation (PPRF)
– Inhibit contralateral abducens
internuclear and motor neurons
brain.phgy.queensu.ca/pare/assets/Oculomotor%20lecture.pdf
Horizontal Saccades
Omnipause Neurons
• Inhibit burst neurons in PPRF
– Prevent saccades
– Activate saccade burst generator
brain.phgy.queensu.ca/pare/assets/Oculomotor%20lecture.pdf
Horizontal Saccades
Superior Colliculus
• Motor command
- PPRF burst neurons
• Trigger command
- Omnipause neurons
brain.phgy.queensu.ca/pare/assets/Oculomotor%20lecture.pdf
Superior Colliculus
Topographic Motor Map
Purves, et al., (2004). Neuroscience
Saccadic Eye Movements
Higher Saccadic Centers
cueflash.com/decks/CONTROL_OF_EYE_MOVEMENTS_-_57
Higher Saccadic Centers
Frontal Eye Fields
Purves, et al., (2004). Neuroscience
Higher Saccadic Centers
Posterior Parietal Cortex
camelot.mssm.edu/~ygyu/clip_image016_0001.jpg
Higher Saccadic Centers
Basal Ganglia
Purves, et al., (2004). Neuroscience
Neural Control of VOR
library.med.utah.edu/kw/animations/hyperbrain/oculo_reflex/oculocephalic2.html
lsda.jsc.nasa.gov/lsda_data/dil_data/msci1083.jpg
Neural Control of Smooth Pursuit
cueflash.com/decks/CONTROL_OF_EYE_MOVEMENTS_-_57