Post on 25-Feb-2016
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Eye Movement Physiology
Frank M. Marchak, Ph.D.Veridical Research and Design Corporation
www.vradc.com
Society for Psychophysiological ResearchSeptember 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
• Elicited by moving objects that produce illusion of head movement or slow head movements undetected by vestibular system
• Visual-ocular response
www.youtube.com/watch?v=KSJksSA6Q-A&feature=relatedimg.springerimages.com/Images/ImagesMD/ATOPH/01/66/WATER_ATOPH01-09-66-003B.jpg
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 www.youtube.com/watch?v=kEfz1fFjU78
• Keep moving stimulus on fovea- Under voluntary control
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/
emedicine.medscape.com/article/1189759-overview
IO SR IO/SR SR/IO SR IO
LR MR MR LR
SO IR SO/IR IR/SO IR SO
MR MR
CONVERGENCE
Ophthalmotrope (Ruete, 1857)
bjo.bmj.com/content/93/5.cover-expansion
Extraocular Muscle Innervation
Extraocular Muscle Innervation
Origins
Purves, et al., (2004). Neuroscience
Extraocular Muscle Innervation
Ocular Motor Neuron Nuclei
Extraocular Muscle Innervation
Ocular Motor Neuron Nuclei
Saccadic Eye Movements
express.howstuffworks.com/gif/body-saccidic-composite.jpg
www.sharpsight.in/images/treatments/eye%20trackers.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). NeurosciencePurves, et al., (2004). Neuroscience
• Discharge frequency directly proportional to position and velocity of eye
brain.phgy.queensu.ca/pare/assets/Oculomotor%20lecture.pdf
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
Neural Control of Saccades
Gaze Centers
cueflash.com/decks/CONTROL_OF_EYE_MOVEMENTS_-_57
• Horizontal- Paramedian pontine
reticular formation (PPRF)
• Vertical- Rostral interstitial
nucleus (rostral iMLF)
Neural Control of Saccades
Horizontal Eye Movements
Purves, et al., (2004). Neuroscience
• PPRF– Phasic signal of abducens
motor neurons
Horizontal Saccades
Excitatory Burst Neurons
brain.phgy.queensu.ca/pare/assets/Oculomotor%20lecture.pdf
• Nucleus prepositus hypoglossi– Tonic signal of abducens motor
neurons
Horizontal Saccades
Tonic Neurons
brain.phgy.queensu.ca/pare/assets/Oculomotor%20lecture.pdf
• Paramedian pontine reticular formation (PPRF)– Inhibit contralateral abducens
internuclear and motor neurons
Horizontal Saccades
Inhibitory Burst Neurons
brain.phgy.queensu.ca/pare/assets/Oculomotor%20lecture.pdf
• Inhibit burst neurons in PPRF– Prevent saccades– Activate saccade burst generator
Horizontal Saccades
Omnipause Neurons
brain.phgy.queensu.ca/pare/assets/Oculomotor%20lecture.pdf
• Motor command- PPRF burst neurons
• Trigger command- Omnipause neurons
Horizontal Saccades
Superior Colliculus
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
lsda.jsc.nasa.gov/lsda_data/dil_data/msci1083.jpg
library.med.utah.edu/kw/animations/hyperbrain/oculo_reflex/oculocephalic2.html
Neural Control of Smooth Pursuit
cueflash.com/decks/CONTROL_OF_EYE_MOVEMENTS_-_57