COMPARISON
OF THE EFFECTS
OF UNILATERAL
AND BILATERAL
EYE CLOSURE
ON CORTICAL
UNIT
RESPONSES
IN KITTENS’
TORSTEN
Neurophysihgy
Harvard
(Received
N. WIESEL
AND
DAVID
H. HUBEL
Laboratory, Department of Pharmacology,
MedicaL School, Boston, Massachusetts
for publication
December
23, 1964)
INTRODUCTION
THE NORMAL
CAT OR KITTEN
about four-fifths of cells in the striate cortex
can be driven by both eyes (3, 4). If, however, one eye of a newborn kitten
is sewn shut and the visual cortex recorded from 3 months later, only a
small fraction of cells can be driven from the deprived eye (8) . In contrast,
many cells in the latera .I geniculate are driven normally
from the d,eprived
),
suggesting
that
the
abnormality
occurs
somewhere
between genicueye (7
late cells and cortex. Since clear receptive-field
orientations
and directional
preferences to movement
are seen in cortical cells of newborn visually inexperienced kittens, the deprivation
effects presumably
represent some sort
of disruption
of innately determined
connections,
rather than a failure of
postnatal development
related to lack of experience.
In these experiments
the use of monocular
deprivation
made it possible
to compare adjacent geniculate layers, and also to compare the two eyes in
their ability to influence cortical cells, so that each animal acted, in a sense,
as its own control. The results led us to expect that depriving both eyes for
similar periods would lead to an almost total unresponsiveness
of cortical
cells to stimulation
of either eye. That should be so, provided the effects of
depriving
one eye were independent
of whether or not the other eye was
simultaneously
deprived. It seemed worthwhile to test such an assumption,
since any interdependence
of the two pathways would be of considerable
interest. We accordingly raised kittens with both eyes covered by lid suture,
and recorded from the striate cortex when the animals had reached an age
of 23-43 months.
IN
METHODS
In 5 kittens the lids of both eyes were sutured together bilaterally 6-18 days after birth,
just before normal eye opening or up to 8 days after (Table 1). Lid closure reduces retinal
illumination
by 4-5 log units (7), and undoubtedly
prevents any form vision. One kitten
was observed behaviorally
at 3 months of age and was kept aside for physiological studies
of recovery (9). Single-cell recordings were made in the other 4 kittens (no. 34) at 24-43
months of age. In all, 10 penetrations
were made and 139 units studied.
1 This work was supported in part by Research Grants NB 02260-06, NB-05554-01,
NB-02253-06
from the National
Institutes
of Health, and in part by Research Grant
AF-49-638-1443
from the U, S. Air Force.
1030
T. N. WIESEL
AND
D. H. HUBEL
In two additional
kittens
the lids of one eye were sutured
before the time of normal
eye
opening.
These
animals
(no. I and 2) were recorded
from
at 8-10 weeks,
and the results,
together
with those from
three monocular
closures
previously
reported
(8), were compared
with the results
of the binocular
closures.
The acute
experiments
were done under thiopental
anesthesia,
and succinylcholine
was injected
intravenously
in order
to paralyze
the extraocular
muscles.
Tungsten
microelectrodes
were used in a closed-chamber
system
(2, 3). Receptive
fields were mapped
by
projecting
smaIl spots of white
light
upon a wide white
tangent
screen,
which
the animal
faced from
a distance
of 1.5 m, A background
light
was set at low photopic
or mesopic
levels ( - 1 to +l log10 cd/mz),
and the intensity
of the stimulating
light was l-l.5
log units
brighter
than the background.
After
the recordings
the animals
were perfused
with
normal
saline
followed
by 10 %
formalin.
The brains
were embedded
in celloidin,
sectioned
at 25 p, and stained
with cresyl
violet.
These histological
sections
were used for reconstruction
of the electrode
tracks
and
for a morphological
study
of the visual pathways.
Methods
of measuring
the size of cells in
the lateral
geniculate
are described
in a previous
paper
(7).
RIBULTS
Monocular closures. In our first series of deprivation
experiments
(8)
three kittens were deprived by monocular
lid closure from birth to 23 to
3 months. Recordings
made at that time gave highly co nsistent results: in
each of th .e 4 penetrations
there were steady su ccessions of cells respondi w
to the eye that had been o Pen, interrupted
by an occasional cell that would
not respon .d to either eye, agai nst an almost continuous bat kground of unresolved unitary
activity
responding
briskly
to the normal eye. With a
single exception, all of the 85 cells recorded gave no response to the previously closed eye, and at no st #age in any of the penetrations
was the unresolved background
responsi ve to tha .t eye.
In the paper that follows (5) it is shown that normal cortical cells are
to some extent segregated with respect to eye dominance.
The possibility
arose that after monocular
deprivation
any cells still influenced from the
deprived eye might be aggregated into small isolated islands, and might
therefore not be encountered
in a small number of penetrations.
We therefore made a more intensive search, recording from 115 more cells in 2 kittens
deprived by monocular
closure from birth to an age of 2-3 months. Five
additional
penetrations
were made, the results of which are shown schematically
in Fig. 1. Each electrode track is expanded so as to illustrate the
relative depths at which cells were recorded. The position of each cell is
represented by a short horizontal
line placed in the appropriate
vertical row
according to ocul ar dominance
positions
of
cells
that
could
not be
group;
driven are shown in a separate row to the right of the others.
Two penetrations
were made in the first of these kittens, and are illustrated to the left in Fig. 1. No cells were driven from the right (deprived)
eye. Cells recorded from the left hemisphere,
al 1 driven from the left eye,
were therefore classed as group 7; cells recorded from th e righ t hemisphere
were all group 1. These two penetrations
were thus similar to almost all of
those made in the previous monocular
deprivation
series.
Three penetrations,
reconstructed
to the right in Fig. 1, were made in
kitten no. 2. Two of these turned out to contain a region in which succes-
UNILATERAL
Kitten
P2
P3
#
2
P4
left
H*mirphOtm
Rqht
Hamlrphtrt
1031
CLOSURE
Kitton
Right
Hcmrsphrte
4
7
3oi
30
tll
L-
-
I
Gtbup
EYE
#I
Pl
L*f t
Htmtrphete
1
4
VS. BILATERAL
4
Group
7
F
-**m
I
4
Gfoup
7
1
Group
4
7
bI
4
7 **--
Group
FIG. 1. Schematic reconstructions
of five microelectrode
penetrations
in two kittens.
Kitten 1 was 8 weeks old and kitten 2,lO weeks; both had the right eye closed by lid suture
at 8 days. Each penetration
extended into cortical gray matter for about 1.5 mm. The
penetrations
are drawn so as to indicate relative positions of individual
celIs; each cell is
represented by a short horizontal
line placed in the appropriate
vertical row according to
ocular-dominance
group. The separate row to the right of group 7 is for unresponsive cells.
The total number of cells in each group is indicated in the histogram at the bottom. (For
definitions of ocular-dominance
groups see legend of Fig. 2.)
sively recorded cells and unresolved backgroud
activity were driven from
both eyes or from the deprived eye alone. Each region formed only a small
portion of the whole penetration.
In the third penetration
cells were driven
entirely by the normal eye, with one exception, a cell that was influenced
by the deprived eye but strongly dominated
by the normal eye.
1032
T. N. WIESEL
AND
D, H, HUBEL
Of the 12 cells that were driven by the deprived eye, all but 1 were abnormal in one way or another. Most of them responded in a vague, unpredictable manner, and most lacked a precise receptive-field
orientation.
Some
showed an unusually
pronounced
decline in responsiveness after several
seconds of repeated stimulation.
Curiously,
some cells were driven abnormally not only from the deprived eye but also from the eye that had been
v74
Normal
1-1
No
orientation
NO
response
I71
-I
1-3
El
FIG. 2, Ocular-dominance
distribution
of 199 cells recorded
in the visual
cortex
of
5 monocularly
deprived
kittens.
The animals were 8-14 weeks
old and all had the
right eye closed by lid suture
from the time
of normal
eye opening.
Shading
indicates
cells that
had the usual
specific
response
properties
to visual
stimulation;
absence
of shading
indicates
cells that lacked
the
speci-ficity.
Internormal
orientation
rupted
lines indicate
cells that did not respond to either
eye. Cells of group
1 were
driven
only
by the contralateral
eye; for
cells of group
2 there was marked
dominance of the contralateral
eye; for group
3,
For
cells
in group
4
slight
dominance.
there
was no obvious
difference
between
the two eyes. In group
5 the ipsilateral
eye
dominated
slightly;
in group
6, markedly,
and in group
7 the cells were driven
only
by the ipsilateral
eye.
Contraloteral
H
OCULAR
Equal
00~
I psilateral
b
ItdANCE
open all along. Similar abnormal
cells were found after binocular deprivation, as described below, and after attempts to induce recovery (9).
Figure 2 shows the ocular-dominance
histogram of all 199 cells recorded
in monocular
deprivation
experiments.
The 13 cells that were influenced
from the deprived eye amounted
to about 7y0 of the total. While this
figure is larger than the original monocular
deprivation
experiments
suggested, it is undoubtedly
more reliable, and confirms our impression
that
the proportion
of cells influenced from the deprived eye is small. The proportion driven normally
must be very small indeed. Perhaps more important
is
the suggestion that such cells may be aggregated in small regions of cortex
which together make up only a small fraction of the total volume.
Binocular CEosure, From the monocular closures one might have expected
UNILATERAL
vs. BILATERAL
EYE
1033
CLOSURE
to fmd large areas of cortex containing
no responsive cells, and only small
islands of tissue with cells responding in an aberrant way to one eye or both.
Right from the outset, however, it was clear that we were not dealing with
cortex in which most cells were unresponsive.
Throughout
the greater part
of all nine penetrations
in kittens no. 3-6, most cells not only responded to
visual stimuli,
but over half of the ones that responded did so normally.
The cortex of these animals was nevertheless
by no means normal.
Numerous
sluggishly responding
unpredictable
cells with vaguely defined
receptive field properties made the penetrations
difficult and frustrating.
Of
139 cells recorded, 45 (327,) were classed as abnormal,
as opposed to 57
(41%) normal cells. Thirty-seven
cells (27y0) could not be driven by visual
Table
-
I. Effects
oJ bilderal
eye closure
.___
-.._--. - .-. c
Kitten
3
Kitten
4
on corkal
.
Kitten
cells
-_-..--
5
-
Age at time of eye closure, days
18
18
Age at time of recording,
months
4%
4
Number
of penetrations
3
3
Normal
cells
Abnormal
but responsive cells
Unresponsive
Totals
--
: 14
(cells)
celIs
12
(36%
31%)
I 13 33%)
39
Kitten
--_
6
6
2%
3
; 2
6
2
.--_-.--
_
Totals
(cells)
17 (46%)
15 (43%
11 (39%)
57 (41%)
10 (2770)
13 (37%)
10 (36%)
45 (32 %)
10 (27%)
7 (20%)
I
; 35
-.-----.
7 (25%)
37 (27%)
37
. . ...- ------.
28
139
stimulation
at all, and were recognized only by their maintained
firing.
The cortex may have contained
unresponsive
cells without
maintained
firing; they would not have been observed, in which case 27% would be
too low. These results are for the 4 kittens taken together, but figures for
the individual
experiments
were in reasonable agreement
(Table 1); the
proportion
of cells that could be driven, normally
or abnormally,
ranged
from 67y0 for kitten no. 3 to 80% for no. 5.
The normal cells showed all of the usual specific responses to properly
oriented
line stimuli.
Some receptive
fields were “simple”
and others
“complex,”
in the sense in which we have used these terms elsewhere (2, 3).
Cells that responded abnormally
had lost much of their specificity for precisely oriented lines, reacting with uniform briskness over a wide range of
angles, and often showing no orientation
preference at all. Some of these
cells were driven from both eyes, and gave abnormal
responses to both.
Like most normal cortical cells, the abnormal
ones generally gave no responses to diffuse light. None had concentric center-surround
fields of the
type found in the lateral geniculate body or retina. Many showed a tendency
to tie actively the ht
time a stimulus was introduced
but with declining
1034
T.
N, WIESEL
AND
D.
H. HUBEL
vigor as the stimulus was repeated. A period of l/2 to 1 min. without stimuli
was usually enough to revive a cell fully. We have observed this behavior in
Or
cells of normal adult cats in all three visual areas, but not as frequently
to as pronounced a degree.
The ocular-dominance
distribution
is shown for one binocularly
deprived kitten (no. 3) in Fig. 3A, and for all four kittens in Fig. 3B. The
majority
of cells could be driven from both eyes. Normal and abnormal cells
were present in all groups in Fig. 3B, though there was probably some de--37
p71
B
.
IN
Normal
1
r-7
0 orieniation
No
L-2
r
1
I
i
response
2(
Controloterol
OCULAR
Equal
Ipsiloterol
DOMINANCE
Contralaterat
N
OCULAR
Equal
lprilatcral
DOMINANCE
3, A I distribution
of 32 cells according to eye preference, in a kitten (no. 3) raised
for the first 3 months with both eyes sutured closed. One penetration
was made in each
hemisphere. B; ocular-dominance
distribution
of 126 cells recorded from the 4 binocularly
deprived kittens (no. 3-6), in 10 penetrations.
FIG.
crease in the proportion
of cells in groups 3-5 compared with the distribution
in normal cats. The most conspicuous abnormality
was seen in the large
group of nonresponding
cells, shown by the interrupted
column to the right
of each histogram.
We have no evidence that unresponsive cells occur in the
normal striate cortex (3, 4).
In Fig. 4 one of three penetrations
made in kitten 4 is reconstructed
in
detail. To the right of the figure is a tracing of a coronal section through the
right postlateral
gyrus. To the left, the electrodo lrack is expanded as in
Fig. 1. Lines within the circles indicate by their tilt the receptive-field
orientation.
As in the normal animal, cells were aggregated according to
receptive-field
orientation.
Within a single column, such as that formed by
I
UNILATERAL
vs. BILATERAL
EYE
CLOSURE
1035
Group
4
‘2
4,s
7
10
13
0
16
i\
23
.
FIG, 4, Reconstruction
of a penetration
through the right postlateral gyrus in a kitten
deprived by bilateral lid suture for the fist 3 months. To the right is a tracing of a coronal
section passing through the electrode track; an electrolytic lesion, made at the end of the
penetration,
is indicated by a circle. This track is expanded to the left of the figure. As in
Fig. 1, cells are indicated by short horizontal
lines placed in the appropriate
vertical rows
according to ocular-dominance
group, and to the right of group 7 is a separate row for unresponsive cells. The total number of cells in each group is indicated by the histogram at the
bottom. To the right of the reconstruction
receptive-field
orientations
are indicated by the
inclination
of the lines inside circles; a circle without a line indicates absence of any clear
receptive-field
orientation
(kitten no, 4).
cells l-10 and 13-16 and indicated
by the large brackets, there were both
normal cells and cells with nonoriented
fields. Unresponsive
cells were sometimes grouped together (cells 23-27), but were also frequently
intermixed
1036
T. N. WIESEL
with more normal cells
tendency for cells to be
nating eye. For example,
lateral eye consistently
cording to eye dominance
more detail in the next
AND
D. H. HUBEL
(12, 19, and 20). Finally,
the figure illustrates
a
aggregated in the cortex according to the predomicells 1-13 form a sequence in which the contradominated.
As mentioned
above, this grouping acis also found in normal cats, and is examined in
paper (5).
Histological
observations
in the visual pathways.
Since the cortical physiology was so different from what might have been expected from the monocular closures, we were anxious to learn whether or not the geniculate
histology would be consistent in the two studies. In monocular
closures (7)
there were marked abnormalities
in the layers receiving input from thedeprived eye, consisting of a change in staining characteristics
of‘cells, a decrease in the volume of cell bodies and nuclei, and a loss of the clear un:
stained substance between cell nests. The changes were obvious at a glance,
on comparing the normal and abnormal layers. The decrease in mean crosssectional area of cell bodies amounted in the dorsal layers to 30-40 yO.
In animals with binocular closure there was surprisingly
little to see on
casual inspection.
This is illustrated
in the photomicrograph
of Fig. 5A.
The difference, however, was apparent rather than real. The changes were
not obvious since abnormal
cells did not stand out against normal ones on
the same slide. Nevertheless,
comparison
with a normal geniculate
as in
Fig. 5B, or with normal layers in monocularly
deprived kittens, showed
that the same abnormalit ties were indeed present, and to an equal degree.
In k itten 3 measurement
of 200 cells in the two dorsal layers (A and Al)
showed a mean cross-sectional area of about 180 p*, compared with a normal
value of about 300 CL*.This represents a shrinkage of about 409& The nucleus
and nucleolus likewise showed marked shrinkage.
No obvious histological
changes were seen on simple inspection of Nissl or myelin sections of retina,
optic nerve, superior colliculus,
or cortex.
Behavioral
effects. As the lid-sutured
kittens grew up they adapted remarkably
well to their blindness. They learned to move about adroitly in
the large room where they were kept, and became so familiar with the objects in the room that a casual observer would hardly have guessed they
could not see. Vision was tested in one kitten at 33 months by observing
its behavior after separating the lids of one eye under a general anesthetic.
The cornea and media appeared normal, the pupillary
reflex was brisk, and
there was no nystagmus.
Tactile placing reactions were present, but there
was no visual placing. As the kitten moved about the room there were no
indications
that visual cues were used; placed in an unfamiliar
room, it
frequently
bumped into large obstacles in its path. We concluded from these
crude behavioral
observations
that for practical purposes the animal was
blind. The result is in agreement with behavioral
studies on animals raised
in darkness (6), and is similar to that obtained
for the deprived eye in
kittens raised with one eye covered (8).
1 mm
FIG. 5. A : coronal section through the right lateral geniculate body of a kitten (no. 3)
in which both eyes were closed for the first 3 months of life. Celloidin, cresyl violet. Same
animal as in Fig. 3A. B: coronal section through right lateral geniculate body of a normal
3-month-old
kitten, for comparison with A.
1038
T. N. WIESEL
AND
D. H. HUBEL
DISCUSSION
reThe experiments
with binocular eye closure confirm the monocular
with virtually
compl .ete
sul ts in showing tha t complete form deprivation
exclusion of light can lead to marked morphological
changes in the geniculate, and marked functional
changes in the cortex. The surprising thing was
not the extent of the physiological
changes, but on the contrary the fact
that they were not more severe. Penetration
after penetration
with little or
no driving of cortical cells from the deprived eye in monocular closures had
led us to expect little or no driving from either eye in the binocular experiments. In all nine penetrations
it was as if the expected ill effects from closing one eye had been averted by closing the other. Taken together, the two
sets of experiments
seem to suggest that early in life the functional integrity
of the pa thway may depe nd not only on th .e amount of afferent impulse
ac tivity,
but also on the in terrelationshi
PS between the various sets of
afferents. This suggestion receives support from the results of the next
paper (5), which describes the cortical effects of interference
with normal
binocular interaction.
The mechanism of this apparent interaction
between the two converging
pathways is at present quite obscure. The site of the interaction
is presumably the cortex, since the evidence so far available indicates that few cells
in the geniculate
receive input from the two eyes. Within
the cortex the
most important
site for anatomical
convergence of the two paths is probably the simple cells, for these seem to be the first cells in the path that
can be driven by both eyes. The similarity
of simple and complex cells in
their ocular-dominance
distribution
suggests that no further binocular convergence takes place at the complex cell (3). No attempt was made in these
experiments
to distinguish
simple and co mplex cells; to sa mple as many cells
as possible we confined our efforts to mapping field position, size and orientation, and ocular dominance.
If simple cells are the site of the interacting
deprivation
effects, it may be possible to learn more about underlying
mechanisms by studying these cells separately.
Regardless of where the interaction
takes place, it is almost as though
the afferent paths were competing for control over the cell, so that a reduction in efficiency in one set of synapses permitted
the other set to take o ver
at the first set’s expense. This could simply be a matter of competition
for
space on the postsynaptic
mem .brane, some synapses sh rinki *ng, 0thers expandi .ng to fi 11 the space, and, as it were, pushing the first ones aside . If
any thing like that did occur one would expect that wi th monocular closure
the effectiveness of the open eye would , on the who lie t be enhanced. Unfortunately, it is difficult to esta blish such an improve ment experimental]
y because of the great variation in briskness of responses from one cell to the next.
A possible way of settling this and other questions would be to look in kittens
for changes in responses of simple cortical cells over periods of many hours or
a few days.
UNILATERAL
vs. BILATERAL
EYE
CLOSURE
1039
Our previous finding that visual experience is not necessary for the formation of specific connections at the striate level (4) is confirmed by the fact
that in the bilaterally
lid-sutured
animals many cells were driven normally.
We have no hint as to why some cells remained apparently
normal while
others became unresponsive
and still others developed
pathological
responses. The presence of a high proportion
of responsive cells in these experiments is consistent with Baxter’s observation
(1) of normal evoked responses
in dark-reared cats.
It remains to comment on the relation between the physiological
findings
in these experiments
and the behavioral defects. Monocular
deprivation
led
to a marked decline in responsiveness of cortical cells to stimulation
of the
deprived eye, which agreed well with the marked blindness in that eye. Binocular deprivation
produced a bilateral blindness even though there were
plenty of responsive cells in the cortex, many of them apparently
normal.
The visual defects found in the two experiments
may thus have different
origins The abnormalities
in area 17 could by themselves account for the loss
of vision following monocular
occlusion. With binocular occlusion one may
have to look for impairment
at levels central to area 17 to explain the blindness we observed, and also that which follows dark rearing (6).
SUMMARY
If a kitten is raised from birth with one eye sutured closed, recordings
from the visual cortex at 3 months show that very few cells can be driven
from the deprived eye (8). As part of the present study these results were
confirmed and extended in two kittens monocularly
deprived for 8-10 weeks.
In the 5 monocularly
deprived kittens studied to date, 13 of 199 cells could
be driven from the previously closed eye; all of these except 1 had abnormal
receptive fields. Cells that responded to stimulation
of the deprived eye
tended to be aggregated into small regions of the cortex, so that over most
penetrations
no responses were seen from the deprived eye. From these results
it was predicted that if animals were binocularly
deprived for similar periods
most of the striate cortex would be unresponsive to stimulation
of either eye.
To test this, the lids of both eyes were sutured together in 5 kittens shortly
after the time of normal eye opening, and the animals raised in normal surroundings to an age of 2+-44 months. Responses in single cells of the striate
cortex were observed in 4 animals. Contrary
to what had been expected,
responsive cells were found throughout
the greater part of all penetrations, and over half of these cells seemed perfectly normal. The cortex was
nevertheless not normal in that many cells responded abnormally,
and many
were completely
unresponsive.
In the fifth kitten an eye was opened and
vision tested. The pupillary
response was normal but the animal from its
behavior appeared to be blind.
Histologically
the lateral geniculate
body showed changes similar to
those found after monocular
deprivation,
but they occurred throughout
all
1040
T. N. WIESEL
AND
D. H. HUBEL
layers bilaterally:
the Nissl-stained
cells appeared pale, cross-sectional areas
of cell bodies were reduced by about 40y0, and the pale substance between
cell nests was greatly reduced in volume. There were no obvious changes in
retinas or cortex.
It thus appears that at the cortical level the results of closing one eye
depend upon whether the other eye is also closed. The damage produced by
monocular
closure may therefore not be caused simply by disuse, but may
instead depend to a large extent on interaction
of the two pathways.
ACKNOWL,EDGMENT
We expresz3 our thanks
technical assistance.
3.
4.
5.
6.
7.
8.
9.
and John Tuckerman,
for their
REFERENCES
Study of the Effects of Sensory Deprivation
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dtirtation;
unpublished).
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HUBEL,
D. H. Single unit activity in striate cortex of unrestrained
cats. J. Physid.,
1959, 147: 226-238.
HUBEL, D, H. AND WIESEL, T.N.
Receptive fields, binocular interaction
and functional architecture in the cat’s visual cortex. J. Physid., X362, MO: 106-154.
HUBEL,
D. H. AND WIESEL, T.N.
Receptive fields of cells in striate cortex of very
young, vhually inexperienced
kittens. J. Neumphysiol.,
1963,26: 994-1002.
HUBEL, D. H. AND WIESEL, T. N. Binocular
interaction
in striate cortex of kittens
reared with artificial squint. J. Neumphysid.,
1965,28: 1041--1059.
as a requirement
for growth and function in behavioral
RIESEN, A. H. Stimulation
development,
In: Functions of Varied Experience, edited by D. W. Fiske and S. R.
Maddi. Homewood, Ill., Dorsey Press, 1961, pp. 57-105.
WIESEL,
T.N. AND HUBEL, D.H.
Effects of visual deprivation
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I. BAXTER,
(doctoral
2.
to Jane Chen, Janet Tobie,