Oculomotor and Vestibular Function · Oculomotor and Vestibular Function Nicholas Sachs USC - BME 620L 11/10/2006 Outline • Why Move the Eyes? ... Pathway Response from the Left

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Oculomotor and Vestibular Function

Nicholas SachsUSC - BME 620L

11/10/2006

Outline

• Why Move the Eyes?• Mechanics of Eye Movement• Types of Eye Movement

– Interaction with the Vestibular System

• Case Study: Vestibular Stimulation• Case Study: Eyeblink Stimulation

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Why Move the Eyes?

Basic Principle Behind All Ocular Movement:

Keep Images Stable on the Retina with Target Centered on the Fovea

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Mechanics of Eye Movement

Degrees of Freedom:

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Degrees of Freedom:3 Axes of Rotation

Elevation

Depression

Extorsion

Intorsion

AbductionAdduction

Actuation:

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Actuation:3 Pairs of Muscles

Superior Rectus

Inferior ObliqueInferior Rectus

Superior Oblique

Lateral RectusMedial Rectus

Extraocular Muscles

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Axis of Rotation

Muscle Action

ExtorsionElevationInferior ObliqueIntorsionDepressionSuperior Oblique

DepressionExtorsionInferior RectusElevationIntorsionSuperior Rectus

In AbductionIn Adduction

AbductionLateral RectusAdductionMedial Rectus

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Muscle Action




AbductionLateral RectusAdductionMedial Rectus

Conjugate Movements




(Right Eye)AbductionLateral Rectus(Left Eye)AdductionMedial Rectus

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Conjugate Movements





Conjugate Movements





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Conjugate Movements





Conjugate Movements





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Conjugate Movements





Conjugate Movements





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Conjugate Movements





Conjugate Movements





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Conjugate Movements





Innervation

IIIInferior Oblique(Trochlear)IVSuperior Oblique

IIIInferior RectusIIISuperior Rectus

(Abducens)VILateral Rectus(Oculomotor)IIIMedial Rectus

NerveMuscle

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Injury:Trochlear

Nerve Damage Affecting

Left Superior Oblique

Types of Eye Movement

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6 Main Types of Movement

• Saccades• Smooth Pursuit• Vergence• Fixation

• Vestibulo-ocular Reflex• Optokinetic Reflex

Target Selection

CompensatoryMovement

6 Main Types of Movement

• Saccades• Smooth Pursuit• Vergence• Fixation

• Vestibulo-ocular Reflex• Optokinetic Reflex

Gaze: combinationof head and eyemovement

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Saccadic Movement

Tonic and Burst Activity

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Tonic and Burst

Neurons

Saccadic Pathway

Motor Circuits for Saccades Lie in Brain Stem

Different Centers for Horizontal and Vertical

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Cortical Planning of Saccades

LGN

V1Parietal

MT and MST

SuperiorColliculus

CaudateNucleus

SubstantiaNigra

Cerebellum

Mesenceph.Ret. Form.

PontineRet. Form.

OculomotorNerves

FrontalEye Field

Using Saccades to Diagnose ADHD - Antisaccade

InstinctNormal

InstinctPathological

Flash

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Smooth Pursuit

Smooth Pursuit

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Cortical Initiation of Smooth Pursuit

Dorsolat.Pont. Nucl.

Cerebellum

VestibularNuclei

PontineRet. Form.

OculomotorNerves

LGN

V1Parietal

MT and MST

FrontalEye Field

Damage to the Smooth

Pursuit Pathway Results in

Saccade-like Movement

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Vergence

Involves Rectus Muscles Only

Organized in Midbrain

Fixation

Rostral Portion of Superior Colliculus

Inhibit Caudal Superior Colliculus and Activate Omnipause Nuerons

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Interaction with the Vestibular System

Vestibular Labyrinth

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Vestibular Hair Cells


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Response of Vestibular System to Rotation

Otolith Organs (Utricle)

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Semicircular Canals(Hair Cells in the Ampulla)

Bilateral Symmetry

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Orientation of Canals Relative to Extraocular

Muscles

Relation Between

Canal Stimulus

and Muscle Activity

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VOR Pathway

Response from the Left Side

When Turning the Head Left

VOR Pathway

Response from the Right Side

When Turning the Head Left

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Tonic and Burst

Activity in VOR

VOR Nystagmus

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VOR and OKN Function

Summary of Oculomotor System

• Purpose - Maintain Foveation• Relatively Simple

– 3 Axes of Rotation, Muscle Pairs, Nerves• 6 Specific Types of Movement• Damage to Parts of the System Results

in Specific Dysfunctions• Tied Closely to Vestibular System

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Case Study:Vestibular Nerve Stimulation

C Della SantinaIEEE-EMBS 2005Shanghai, China

How to Design a Prosthetic System for Sensory Function

• What does it sense?– (How can we replicate it?)

• How does it code for this?– (How can we replicate it?)

• Where are signals sent?– (Where can we intervene?)

• How do we know it’s working?

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How to Design a Prosthetic System for Sensory Function

• What does it sense? - acceleration– (How can we replicate it?) -

accelerometers• How does it code for this? - spike freq.

– (How can we replicate it?) - stim. w µ-contr.• Where are signals sent? - vest. nerve

– (Where can we intervene?) - vest. nerve• How do we know it’s working? - VOR

Natural aVOR for Chinchilla Rotated in Each Vestibular

Plane

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aVOR Response in Chinchilla with Electrical Stimulation

Crosstalk in aVOR Response with Electrical Stimulation

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Case Study:Eyeblink Stimulation

N Sachs, E Chang, and J WeilandDoheny Eye Institute

USC - BME

The Pain• Damage to the 7th cranial

(facial) nerve can cause loss of eye blink function

• Without treatment this can lead to eye damage and loss of vision

• Current treatments are functionally unappealing

Paralyzed Functional

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Palpebral Part (blinking)

Orbicularis Oculi(innervated by 7th nerve)

Levator Palpebrae(innervated by 3rd nerve)

Orbital Part (squinting)

Electrical stimulation of paralyzed orbicularis oculi can restore a functionally and cosmetically acceptable blink

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Methods• Developed animal model

of orbicularis paralysis by sectioning 7th nerve

• Separated rabbits into groups based on duration of paralysis

• At end of specified period inserted electrode into upper eyelid

• Stimulated acutely with biphasic current pulses and recorded response with high speed camera

Electrode PlacementElectrode Contacts

Upper Lid Margin

Lower Lid Margin

Medial Canthus

Nictitating Membrane

Electrode Inserted into Rabbit Upper Eyelid

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Experimental Setup

PC

SBC Connector

Block

DAQ

PCI-6025E

Stimulus Isolator (V → I)

IMAQ

PCI-1428

Camera

1M75

Power Supply

Camera Link Cable

Analog Out

190 frames/s0.083mm res

c(chronaxie)

b(rheobase)

* Geddes and Bourland, 1985

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* Geddes and Bourland, 1985

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Chronaxie & Rheobase Values

Rheobase (mA) Chronaxie (ms)Normal 0.480 +/- 0.259 0.367 +/- 0.1111-week 0.044 +/- 0.011 50.97 +/- 10.854-week 0.054 +/- 0.042 47.34 +/- 21.358-week 0.034 +/- 0.015 56.93 +/- 27.4016-week 0.570 +/- 0.342 0.518 +/- 0.549

Motor Nerve 0.08 – 0.60*Denervated Muscle 11 – 30*

* Geddes, 1999

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Data Analysis

1. Trace outline of palpebral fissure prior to stimulation and measure area in pixels.

2. Trace outline of palpebral fissure at peak of closure during stimulation and measure area in pixels.

3. Divide area during stimulation by area prior to stimulation to get percent closure.

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Experimental Setup

PC

SBC Connector

Block

DAQ

PCI-6025E

Stimulus Isolator (V → I)

IMAQ

PCI-1428

Camera

1M75

Power Supply

Camera Link Cable

Analog Out

190 frames/s0.083mm res

EMG Amplifier

Mirror Setup

Measuring Eye Movement

• High Speed Video

• EMG of Active Muscle

• Eye Coils in External Magnetic Field

• Electro-oculogram (EOG)

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Electro-oculogram(EOG)

Measuring DC corneoretinal potential caused by high

metabolic rate in the retina

EOG Electrode Setup

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EOG Recording

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Bilateral Symmetry

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VOR Pathway

3 Axes of RotationElevation

Depression

Extorsion

Intorsion

AbductionAdduction

Documents

Oculomotor and Vestibular Function · Oculomotor and Vestibular Function Nicholas Sachs USC - BME 620L 11/10/2006 Outline • Why Move the Eyes? ... Pathway Response from the Left