the neural control of eye movements - mit opencourseware · 2001. 11. 26. · topics: 1. basics of...
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The neural control of eye movements
Peter H. Schiller
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The problems we are trying to solve in a nutshell
Image removed due to copyright restrictions.
New Yorker, 2001
2
Please see lecture video or Jack Ziegler, "Cat Thinks of a Complex
Equation to Get a Ball Off a Table," New Yorker, November 26, 2001.
Topics:
1. Basics of eye movements
2. The eye plant and the brainstem nuclei
3. The superior colliculus
4. Visual inputs for saccade generation
5. Cortical structures involved in saccadic eye-movement control
6. The effects of paired electrical and visual stimulation
7. The effects of lesions on eye movement
8. Pharmacological studies
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1. Basics of eye movements
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Why do we move our eyes?
A. To acquire objects for central viewing
Saccadic eye movements
B. To maintain objects in foveal view
Pursuit eye movements
C. To stabilize the world on the retina
Vestibulo-ocular reflex, accessory optic system
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Classification of eye movements Conjugate eye movements
saccadic (acquires objects for central viewing)
smooth pursuit (maintains object on fovea)
Vergence eye movements
X Y
1
2
X Y
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X = Y X = Y
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Rene Magritte National Gallery of Art, Washington, DC
Image removed due to copyright restrictions.
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Please see lecture video or Rene Magritte's Le blanc-seing.
Image removed due to copyright restrictions.
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Please see lecture video or Rene Magritte's Le blanc-seing.
Saccadic eye movements made under free-viewing conditions by a subjet examining a picture of the bust of Nefertiti. By Yarbus
Image removed due to copyright restrictions.
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Please see lecture video.
Ashley Bryan
Image removed due to copyright restrictions.
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Please see lecture video.
Free viewing by intact monkey
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2. The eye plant and the
brainstem nuclei
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Innervated bySuperior Trochlear Nerve
Rectus Muscle
LateralRectus Muscle
InferiorRectus Muscle
Innervated byAbducens Nerve Inferior
Oblique Muscle
SuperiorOblique Muscle
MedialRectus Muscle
Other recti and inferior oblique innervated by oculomotor nerveImage by MIT OpenCourseWare.
Cranial nerves 1 2 3 4 5 6 7 8 9 10 11 12
On old olympus' towering top a fat armed girl vends snowy hops
1. olfactory olfaction 2. optic vision 3. oculomotor eye movements, pupil, lens, tears 4. trochlear eye movements, superior rectus 5. trigeminal facial sensations, chewing 6. abducens eye movements, lateral rectus 7. facial facial muscles, salivary glands, taste 8. auditory audition 9. glossophayngeal throat muscles, salivary glands, taste 10. vagus parasympathetic, organ sensation, taste 11. spinal accessory head and neck muscles 12. hypoglossal tongue and neck muscles
Spinal nerves cervical 8 thoracic 12 lumbar 5 sacral 5 coccygeal 1
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Neuronal discharge in oculomotor nucleus
1 second
Up 30
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0
15
30
Down Vertical eye movements
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30150
1530
30150
1530
1 secondUnit Z-2-6
Image by MIT OpenCourseWare.
Responses of a neuron in the oculomotor nucleus that innervates the inferior rectus
Theds
225
200
175
150
125
100
75
50
25
40 30 20 10 0 10 20 30 40
Spik
es p
er se
cond
Right Left
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Image by MIT OpenCourseWare.
The The discharge of four oculomlotor neurons as a function of the angular deviation of the eye
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10 25 50 80 120 ms
25 A500 HZ
µ
Image by MIT OpenCourseWare.
Electrical stimulation of the abducens nucleus
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The discharge patterns and connections of neurons in the horizontal burst generator.Left: Firing patternsfor an on-direction (first vertical dashed line) and off-direction (second dashed line) horizontal saccade ofsize θ to a target step (schematized in the eye and target traces below); Right: Excitatory connections areshown as open endings inhibitory connections are shown as filled triangles, and axon collaterals of unknowndestination (revealed by intracellular HRP injections or postulated in models) are shown without terminals.Connections known with certainty are represented by thick lines.Uncertain connections by thin lines,and hypothesized connections by dashed lines. A complete description of the behavior of this neural circuit is found in the text.The abbreviations here and in figure 4 identify excitatory (EBN) and inhibitory (IBN) burstneurons, long-lead burst neurons (LLBN) , trigger input neurons (TRIG), omnipause neurons (OPN), tonic neurons (TN), and motoneurons (MN).
Target
Eye
OPN
LLBN
EBN
TN
MN
IBN
SuperiorCelloulus
TRIG
EBN
OPN
LLBN
MN
TN
MN
IBN IBN
EBN
LateralRectus
mid
line
θθ
Image by MIT OpenCourseWare.
Brainstem inputs to oculomotor, trochlear and abducens nuclei
BSBS
rate code
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3. The superior colliculus
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TOAD
RABBIT
MONKEY
Image by MIT OpenCourseWare.
Arrows point to optic tectumin three species.
Optic tectum = superior colliculus
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Midline sagittal section through monkey brain
Image by MIT OpenCourseWare.
Superior colliculus
V1lunate
Coronal section through the cat superior colliculus
Figure removed due to copyright restrictions.
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Please see lecture video or Figure 3 of Kanaseki, T., and J. M. Sprague. "Anatomical
Organization of Pretectal Nuclei and Tectal Laminae in the Cat." Journal ofComparative Neurology 158, no. 3 (1974): 319-37.
Visual field representation in the superior colliculus
Contralateral Visual Hemifield
anterior posterior
medial
lateral
Superior Colliculus
2
2
4
4
1 13 3
up
down
foveal peripheral
25
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ON OFF900 msec
19.2O
10.0O
3.5O
1.8O
1.0O
.3O
40s/b
Image by MIT OpenCourseWare.
Visual response of superficial collicular cells
20o
1 second
HEM
unit
VEM
HEM
unit
VEM
27Image by MIT OpenCourseWare.
Responses of a neuron in the superior colliculus with eye movement
data collection
5 o
10
15 o
o
left
up
down
Saccade-associated discharge in a collicular cell
right
each point represents the direction and amplitude of a saccade made during
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Recording and stimulation in the superior colliculus
Recording and stimulation at three collicular sites
SC
lateral
1 2 3 posterior
visual field
3
2
1
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10 25 50 80 120 240 480 ms
10 25 50 80 120 ms
25 A500 HZ
µ
5 Α500 Η Z µ
S.C
1400 ms
1 sec
20o
Abducens nucleus
Superior colliculus
30Image by MIT OpenCourseWare.
Electrical stimulation of the abducens and the superior colliculus
Basic principle of coding in the superior colliculus
A saccade is generated by computing the size and direction of the saccadic vector needed to null the retinal error between the present and intended eye position.
saccadic vector
1
2
RF in SC
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BS
SC
BS
rate code
vector code
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4. Visual inputs for saccade
generation
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MIDGET SYSTEM PARASOL SYSTEM W SYSTEM
koniocellular cells
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V1
123456
1-2 = magno
LGN
Lamina:
interlaminar
3-6 = parvo
M
P K
P
M
K1
?
SC
K2
??
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Antidromic activation method
stimulate
record
antidromic activation
record
V1
W-like cells
Layer 5 complex cells
Superior colliculus
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Cooling method
V
record
LGN
1
cooling plate record
?g
Superiorcolliculus
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500 msec
ON OFF
Beforecooling
Cooled
Aftercooling
Stimulus
Superficial layer Intermediate layer
Image by MIT OpenCourseWare.
Recording in the superior colliculus while cooling V1
Coronal section through the superior colliculus of a monkey whose right visual cortex
has been removed. Lesion marks location where cells can no longer be visually driven.
Image removed due to copyright restrictions.
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Please see lecture video.
Tissue block with injections
inject blocker
V
Parvo
Magno
LGN
1
record
Superiorcolliculus
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SC cell 1 SC cell 2
Parvo Block Magno Block
Normal Normal
80
40
50
25
80
40
50
25
Image by MIT OpenCourseWare.
Single-cell responses in SC while blocking parvo or magno LGN
cortex
colliculus
brainstem
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BS
MidgetV1
LGN
Midget
rate code
P
PARIETAL LOBE
w SC
vector code
MT
Mixed
Parasol
Parasol
Posterior system
w
?M
TEMPORAL LOBE
2
V4
V2V
BS
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Summary
1. Classes of eye movements are vergence and conjugate, with the latter
comprised of two types, saccadic and smooth pursuit.
2. Eye movements are produced by 6 extraocular muscles that are innervated
by axons of the 3rd, 4th and 6th cranial nerves.
3. The discharge rate in neurons of the final common path is proportional to the angular deviation of the eye. Saccade size is a function of the duration of the high-frequency burst in these neurons.
4. The superior colliculus codes saccadic vectors whose amplitude and direction is laid out in an orderly fashion and is in register with the visual receptive fields.
5. The retinal input to the SC comes predominantly from w-like cells. The cortical downflow from V1 is from layer 5 complex cells driven by the parasol system.
6. The superior colliculus is under cortical control.
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