Eye Movements
Last edited October 12, 2009
If the sence of sight be
wonderfull,
the member or instrument serving for the same can not but goe beyond
all
wonder; for it is framed so cunningly, and of such beautifull parts, as
that there cannot be the man which is not ravished with the
consideration
of the same...
The muscles were of necessitie provided and
given to the eye, that so it might move on every side; for if the eye
stoode
faste and immoveable, we should be constrained to turne our head and
necke
(being all of one peece) for to see; but by these muscles it now moveth
it selfe with such swiftness and nimbleness, without stirring of the
head
as is almost incredible...
A. Du Laurens (1599) A Discourse of the
Preservation of Sight: of Melancholike Diseases; of Rheumes, and of Old
Age
Introduction
-
Visual basis for eye movements
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The primate eye
-
Need to look to see...
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Need for accurate visually guided movements
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Stablized images disappear
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Active, self-generated movement necessary for adaptation and development
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Retinal topography
-
but cannot see when you look.
-
Gaze holding
- Vestibulo-ocular reflex
- Optokinetic reflex
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Gaze shifting
-
History
-
A. Du Laurens, 1599, one of the earliest detailed descriptions of the
anatomy
of the eye and associated musculature as well as theories of vision.
-
F.C.
Donders
-
1846, observed that for each direction of gaze the eyes assume the same
position. Helmholtz (1866) called this Donder's
law.
-
1862, earliest reliable measurements of the center of rotation of the
eye
-
1868, conceived of using reaction times to measure speed of mental
operations
using subtraction method
-
J.B. Listing
-
observed that when the eye moves to any position from the primary
position,
it rotates about an axis that is perpendicular to the initial and final
directions of gaze at the point of their intersection. Listing's
law formulated and named by C.G.T. Reute in 1853
-
E. Hering
-
Hering's law - during conjugate eye movements each eye receives equal
innervation
-
Relation
of eye movements and attention
The movements from one point of fixation
to
another are occasioned and regulated by the changes of place of the
attention.
When an object, seen at first indirectly, draws our attention to
itself,
the corresponding movement of the eye follows without further ado, as a
consequence of the attention's migration and of our effort to make the
object distinct. The wandering of the attention entails that of the
fixation
point. Before its movement begins, its goal is already in consciousness
and grasped by the attention, and the location of this spot in the
total
space seen is what determines the direction and amount of the movement
of the eye. (1880) in Hermann's Handbuch der
Physiologie
-
E. Landolt
-
1891, coined term 'saccade' to describe rapid eye movements made during
reading
-
R. Dodge
-
1902, First identification of different types of eye movements
-
1920s
-
first recordings of electrooculogram
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1950s
-
Accurate recording techniques (Yarbus)
-
Examined question of vision during stablized image
-
Beginning analysis using ideas from feedback control systems
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1960s
-
New recording techniques
-
relative reflection of light from limbus, Rashbass; Stark & Young
-
video image of eye, Mackworth
-
invention of scleral search coil, Robinson
-
Improved data on mechanics of saccadic and pursuit eye movements
-
1970s
-
Physiology in alert, behaving monkeys
-
Development of concrete models of saccade generation
-
1980s
-
Clarification of the involvement of more structures in gaze control, in
particular cortical areas, thalamus and basal ganglia
-
1990s
-
Begin work on problems of target selection and fixation duration,
attention
Neural basis of saccadic eye
movements
- Extraocular muscles
- Force pattern to produce saccades
-
Brainstem
- Burst cells
-
Eye velocity
-
Dynamic motor error
- Tonic cells
-
Eye position
-
Neural integrator
- Pause cells
- Circuitry
- The brainstem saccade generator is controlled by a network
of structures in the forebrain
-
Superior colliculus
- Visual neurons
-
Receptive field
-
Visual field map
-
Enhancement
- Movement neurons
-
Basal ganglia
- Caudate nucleus
- Substantia nigra
- Inhibition of the superior colliculus
-
Cerebral cortex
- The problem of saccade target selection
- Many things to look at, but you can only look at one at a time
- The eyes must move to see, but vision is impaired during
saccades, so a
judicious balance must be achieved.
- Frontal eye field
- Visual neurons
- Movement neurons
- Supplementary eye field
