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