sensory motor integration - mcgovern medical school
TRANSCRIPT
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SENSORY MOTOR INTEGRATIONSENSORY-MOTOR INTEGRATION
Valentin Dragoi
Department of Neurobiology and Anatomy
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Outline
• Oculomotor reflex responses
• Eye movements
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Outline
• Oculomotor reflex responses
• Eye movements
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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
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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.
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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
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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.
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PUPILLARY LIGHT REFLEX
Iris sphincter innervated by axons of the short ciliary nerve.p y y
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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
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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
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Outline
• Oculomotor reflex responses
• Eye movements
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WHY STUDY EYE MOVEMENTS?
Adapted from Yarbus, 1967
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Why do eyes need to move?Why do eyes need to move?
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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…
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Eye movements during free viewing
1 deg
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We make 3-4 eye movements each second
3500 N=72,448
2500
3000
ns
1500
2000
of fi
xatio
n
1000
1500
Num
ber
0
500
70 170 270 370 470 57070 170 270 370 470 570
Fixation time (ms)Dragoi and Sur, 2006
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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
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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
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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.
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The response of abducens neurons controls the movement of eyes
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VOLUNTARY (GUIDED) SACCADES
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POSTERIOR PARIETAL CORTEX
Uninteresting targetTarget of
Posterior parietal cortexUninteresting target interest
On off
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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
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VOLUNTARY (GUIDED) SACCADES
FRONTAL EYE FIELDInitiates voluntary movementsComputes direction & amplitudeComputes direction & amplitudeof the saccades
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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.
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VOLUNTARY (GUIDED) SACCADES
FRONTAL EYE FIELD• Initiates voluntary movements
SUPERIOR COLLICULUS• Integrates afferent inputs • Provides control signals• Provides control signals
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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
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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
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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
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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
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Lesions of the superior colliculus permanently abolish the production of “express” saccades.
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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
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Frontal eye field projects back to parietal cortex (which projects to the visual cortex) to confirm target selection
Armstrong and Moore, 2003
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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
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Responses during vertical pursuit in f t l fi ldfrontal eye field
Fukushima et al., Nature, 2002
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Humans look preferentially at high contrast image regionsimage regions
Reinagel and Zador, Network, 1999
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Fixation patches contain significant orientation signals
0.75 Patch 1
signals
0.5
e (x
103 )
Patch 2
0
0.25
n m
agni
tude
Patch 1
1
1.5
2
Orie
ntat
io Patch 2
0
0.5
0 30 60 90 120 150 180
Pixel orientation (o)1o
Dragoi and Sur, J. Cogn. Neurosci, 2006
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Successive fixations tend to land on similar or largely different image patches
110 successivecontrol(%
max
)
90
100
fixat
ions
(
80
cess
ive
f
60
70
cy o
f suc
c
50
60
0-15 15-30 30-45 45-60 60-75 75-90Freq
uenc
00 15 15 30 30 45 45 60 60 75 75 90F
Orientation difference between fixation patches (o)Dragoi and Sur, J. Cogn. Neurosci, 2006
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Effects of frontal eye field and dorsomedial frontal cortex lesions on visually guided eye movements
(S hill d Ch 1998)(Schiller and Chou, 1998)
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Effects of FEF/MEF lesions on visually guided eye movements (Schiller and Chou, 1998)
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Effect of FEF lesion on the timing of saccadic t (S hill d Ch 1998)eye movements (Schiller and Chou, 1998)
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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
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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
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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
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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
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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
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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
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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