SENSORY MOTOR INTEGRATIONSENSORY-MOTOR INTEGRATION

Valentin Dragoi

Department of Neurobiology and Anatomy

Outline

• Oculomotor reflex responses

• Eye movements

Outline

• Oculomotor reflex responses

• Eye movements

CRANIAL NERVES INVOLVED IN OCULOMOTOR CONTROL

Optic nerve: CN IIOculomotor nerve: CN IIITrochlear nerve: CN IVTrochlear nerve: CN IVTrigeminal nerve: CN VAbducens nerve: CN VIFacial nerve: CN VIIFacial nerve: CN VIIVestibulocochlear nerve: CN VIII

EYE BLINK REFLEX

• Protects cornea from damage by foreign objects

• Free nerve endings of 1O trigeminal afferents detectthe foreign object on the cornea

• Eye lid closes rapidly to remove the object

• A bilateral response i.e., there is a direct and a consensual response.

• A “simple” reflex response involving the afferent,two interneurons efferent and the obicularis oculitwo interneurons, efferent and the obicularis oculi.

EYE BLINK REFLEX CIRCUIT

Free nerve endings ongthe cornea> Trigeminal nerve to

i l i i lSpinal trigeminalnucleus to

Reticular formationReticular formation> Bilaterally to

Facial motor nucleiFacial motor nuclei> Facial nerves to

Obicularis oculi of eyelids

PUPILLARY LIGHT REFLEX

Protects photoreceptors from over exposure to light

Photoreceptors detect the light level & forward theinformation via the retinal neurons & optic nerveto the brain

Pupil constricts rapidly to reduce light entering the eye

A bilateral response i.e., there is a direct and a consensual response.

A reflex response involving 1o, 2o & 3o visual afferents,a midbrain motor control structure an autonomic

consensual response.

a midbrain motor control structure, an autonomicganglion & nerve and the iris sphincter.

PUPILLARY LIGHT REFLEX

Iris sphincter innervated by axons of the short ciliary nerve.p y y

PUPILLARY LIGHT REFLEX

Retinal neurons> Optic nerve, chiasm & tract

B hi f h i> Brachium of the superiorcolliculus to

Pretectal Area> Posterior commissure +

bilaterally to

Edinger-Westphal Nucleusg p> Oculomotor nerve to

Ciliary Ganglion> Sh t ili t> Short ciliary nerve to

Iris sphincter

Optic nerve

Optic tract

Optic chiasm

L t l

Hypothalamus: regulation of circadian rhythms

Lateral geniculate nucleus Pretectum: reflex

control of pupil and lens

Optic radiation

Striate cortex

Superior colliculus: orienting the movements of head and eyes

cortex

Outline

• Oculomotor reflex responses

• Eye movements

WHY STUDY EYE MOVEMENTS?

Adapted from Yarbus, 1967

Why do eyes need to move?Why do eyes need to move?

High Visual Acuity is Limited to the Fovea…

fovea

y

1.0

fovea

sual

Acu

ity

0.5

Vis

0-50 500

Eccentricity (deg.)

So the Fovea Must Move…

Eye movements during free viewing

1 deg

We make 3-4 eye movements each second

3500 N=72,448

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xatio

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70 170 270 370 470 57070 170 270 370 470 570

Fixation time (ms)Dragoi and Sur, 2006

LOWER MOTOR NEURONS: Innervate striated muscles

Horizontal movements: Medial & Lateral Rectus MusclesVertical movements: Inferior & Superior Rectus MusclesVertical movements: Inferior & Superior Rectus MusclesRotation: Inferior & Superior Oblique Muscles

Optic nerve: CN IIOculomotor nerve: CN IIITrochlear nerve: CN IVTrochlear nerve: CN IVTrigeminal nerve: CN VAbducens nerve: CN VIAbducens nerve: CN VIFacial nerve: CN VIIVestibulocochlear nerve: CN VIII

COORDINATING ACTIONS OF MUSCLES

Abducens interneurons coordinate the actions of the lateral rectusAbducens interneurons coordinate the actions of the lateral rectusof one eye with the medial rectus of the opposite eye.

The response of abducens neurons controls the movement of eyes

VOLUNTARY (GUIDED) SACCADES

POSTERIOR PARIETAL CORTEX

Uninteresting targetTarget of

Posterior parietal cortexUninteresting target interest

On off

The activation of parietal cortex neurons are particularly sensitive to salient visual stimuli and they respond mostsensitive to salient visual stimuli and they respond most when a stimulus within their receptive field is a saccade target.g

VOLUNTARY (GUIDED) SACCADES

FRONTAL EYE FIELDInitiates voluntary movementsComputes direction & amplitudeComputes direction & amplitudeof the saccades

The activity of frontal eye fields neurons reflects the selection of the visual target for a saccadic eye movement when several potential g f y pgoals for movements are available.

VOLUNTARY (GUIDED) SACCADES

FRONTAL EYE FIELD• Initiates voluntary movements

SUPERIOR COLLICULUS• Integrates afferent inputs • Provides control signals• Provides control signals

Superior colliculus: topographic motor map created by neurons responding prior to saccades of specificneurons responding prior to saccades of specific direction and amplitude, independent of the initial eye positionp

Superior colliculus Visual space

VOLUNTARY (GUIDED) SACCADES

FRONTAL EYE FIELD• Initiates voluntary movements

SUPERIOR COLLICULUS• Integrates afferent inputs

GAZE CENTERS• Vertical Gaze in midbrain

l G• Horizontal Gaze in pons• Direction of saccades

- Co-ordinates actions offsynergist & antagonistmuscles

VOLUNTARY (GUIDED) SACCADES

FRONTAL EYE FIELD• Initiates voluntary movements

SUPERIOR COLLICULUS• Integrates afferent inputs

GAZE CENTERS• Vertical Gaze in midbrain

l G• Horizontal Gaze in pons• Direction of saccades

LMN: Lower Motor Neurons• Oculomotor nucleus • Trochlear nucleusochlea nucleus• Abducens nucleus

Saccade amplitude

VOLUNTARY (GUIDED) SACCADES

FEF projects directly to PPRF

FEF can control eye movements independently of SC

SC lesions produce a permanent deficit in the ability to produce h t l t “ ” dshort-latency “express” saccades

FEF lesions produce permanent lesions p oduce pe manentdeficits in the ability to make saccades not guided by targets

Lesions of the superior colliculus permanently abolish the production of “express” saccades.

VOLUNTARY (GUIDED) SACCADES

FRONTAL EYE FIELD• Initiates voluntary movements

• Frontal eye field = > • Caudate nucleus =>

• Substantia nigra =>• Modulate Superior Colliculus

SUPERIOR COLLICULUS• Integrates afferent inputs

Modulate Superior Colliculus

• Integrates afferent inputs• Corrects control signal

DORSAL VISUAL STREAM feedbackDORSAL VISUAL STREAM - feedback• Posterior Parietal Visual Association Cortex• Determines whether visual target in sight

Frontal eye field projects back to parietal cortex (which projects to the visual cortex) to confirm target selection

Armstrong and Moore, 2003

SMOOTH PURSUIT EYE MOVEMENTS“Follow the object” - spatial orientation & movement detectionFollow the object spatial orientation & movement detection

TEMPORAL EYE FIELD• Target direction & velocity

FRONTAL EYE FIELD• Initiates execution of move

DL PONTINE NUCLEI• Eye direction & velocity

CEREBELLUM • vestibular component• integrate afferent inputs

VESTIBULAR NUCLEI• Medial & Superior nuclei >

• integrate afferent inputs

Medial & Superior nuclei • Medial longitudinal fasciculus• Co-or synergist & antagonist LMN

Responses during vertical pursuit in f t l fi ldfrontal eye field

Fukushima et al., Nature, 2002

Humans look preferentially at high contrast image regionsimage regions

Reinagel and Zador, Network, 1999

Fixation patches contain significant orientation signals

0.75 Patch 1

signals

0.5

e (x

103 )

Patch 2

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agni

tude

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ntat

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Pixel orientation (o)1o

Dragoi and Sur, J. Cogn. Neurosci, 2006

Successive fixations tend to land on similar or largely different image patches

110 successivecontrol(%

max

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90

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fixat

ions

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Orientation difference between fixation patches (o)Dragoi and Sur, J. Cogn. Neurosci, 2006

Effects of frontal eye field and dorsomedial frontal cortex lesions on visually guided eye movements

(S hill d Ch 1998)(Schiller and Chou, 1998)

Effects of FEF/MEF lesions on visually guided eye movements (Schiller and Chou, 1998)

Effect of FEF lesion on the timing of saccadic t (S hill d Ch 1998)eye movements (Schiller and Chou, 1998)

DAMAGE TO UPPER MOTOR NEURONS

EXAMPLE 3 SYMPTOMS: NON-OCULARRIGHT HEMIPLEGIA

NON-FLUENT APHASIASYMPTOMS BOTH EYES

EXAMPLE 3

Broca’s aphasia Right handed SYMPTOMS: BOTH EYES

PUPILS & EYELIDS NORMAL LATERAL GAZE PREFERENCE

FAIL CONJUGATE “GAZE” RIGHT

Right-handedLeft hemisphere

FAIL CONJUGATE GAZE RIGHT

Left LateralGaze Preference

Normal Saccades to Left

Loss of Saccades to Right

FAILURE OF VOLUNTARY SACCADES TO THE RIGHT

DAMAGE TO UPPER MOTOR NEURONS

EXAMPLE 3 SYMPTOMS: NON-OCULARRIGHT HEMIPLEGIA

NON-FLUENT APHASIASYMPTOMS BOTH EYES

EXAMPLE 3

Broca’s aphasia Right handed

Right Hemiplegia Precentral gyrus

SYMPTOMS: BOTH EYESPUPILS & EYELIDS NORMAL LATERAL GAZE PREFERENCE

FAIL CONJUGATE “GAZE” RIGHT

Right-handedLeft hemisphere Left hemisphere

FAIL CONJUGATE GAZE RIGHT

LEFT FRONTAL CORTEX LESIONLEFT FRONTAL CORTEX LESIONAFFECTING THE FRONTAL EYE FIELDAFFECTING THE FRONTAL EYE FIELDC NG ONC NG ONLOSE VOLUNTARY SACCADES TO THE RIGHT

DAMAGE TO UPPER MOTOR NEURONS

EXAMPLE 3 SYMPTOMS: NON-OCULARRIGHT HEMIPLEGIA

NON-FLUENT APHASIA

EXAMPLE 3

Broca’s aphasia Right handed

Right Hemiplegia Precentral gyrusRight-handed

Left hemispherePrecentral gyrusLeft hemisphere

Guyton, Figure 19.5, pg. 242

DAMAGE TO UPPER MOTOR NEURONS

SYMPTOMS BOTH EYESSYMPTOMS: BOTH EYESPUPILS & EYELIDS NORMAL

EYES WANDER AT RESTJERKY PURSUIT LEFT

EXAMPLE 4Wernicke’s aphasia

Right handed JERKY PURSUIT LEFTRight-handedLeft hemisphere

SMOOTH PURSUITSMOOTH PURSUITcontrolled by Temporal Eye Field

DAMAGE TO UPPER MOTOR NEURONS

SYMPTOMS BOTH EYESSYMPTOMS: BOTH EYESPUPILS & EYELIDS NORMAL

EYES WANDER AT RESTJERKY PURSUIT LEFT

EXAMPLE 4Wernicke’s aphasia

Right handed JERKY PURSUIT LEFTRight-handedLeft hemisphere

SMOOTH PURSUITSMOOTH PURSUITcontrolled by Temporal Eye Field

Cortical Input to theCortical Input to theIpsilateral DLPNDLPN lost

DAMAGE TO UPPER MOTOR NEURONS

EXAMPLE 4Wernicke’s aphasia

Right handed

SYMPTOMS: BOTH EYESPUPILS & EYELIDS NORMAL

EYES WANDER AT RESTJERKY PURSUIT TO LEFTRight-handed

Left hemisphereJERKY PURSUIT TO LEFT

Frontal eye field used to “track” visualtarget. But the movement is “jerky”because they are saccades.

LEFT TEMPORAL EYE FIELD LESIONLEFT TEMPORAL EYE FIELD LESIONAFFECTS SMOOTH PURSUIT TO THE LEFTAFFECTS SMOOTH PURSUIT TO THE LEFT

DAMAGE TO UPPER MOTOR NEURONS

SYMPTOMS NON OCULARSYMPTOMS: NON-OCULARIMPAIRED COMPREHENSION

FAILURE TO REPEAT

EXAMPLE 4Wernicke’s aphasia

Right handedRight-handedLeft hemisphere

Guyton, Figure 19.5, pg. 242