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Effect of monocular light-deprivation on leucine uptake in the retina and the optic centres of the newborn rat
Exptl Eye Re3. (1967) 6, 299-302
Effect o f M o n o c u l a r Light-deprivation on L e u c i n e U p t a k e in the R e t i n a and the O p t i c Centres o f the N e w b o r n R a t G. MARAINI, 1~'. CAR'rA, n . , FRANGUELLI AND ~I. SA2~TORI University Eye Clinic, University of Parma, Italy (Received 20 March 1967, London) Monocular light.deprivation"irrno~vbornrats, shortly after the period of normal eye opening, produces a significant decrease of [aH]lcuoine incorporation, and of cellular surface, in the ncurolm of the lat.eral geniculate nucleus connected with the closed eye. No modification of amino acid uptake was detected in the different cellular layers of the retina and of the visual cortex. 1. I n t r o d u c t i o n
The i m p o r t a n c e of a n o r m a l sensory s t i m u l a t i o n on t h e d e v e l o p m e n t and f u n c t i o n a l efficiency of t h e eye a n d of t h e optic ccntres is now g e n e r a l l y a d m i t t e d a n d has r e c e n t l y been stressed b y t h e i m p o r t a n t c o n t r i b u t i o n s of Wiesel a n d ]=Iubel (1963a,b, 1965). These a u t h o r s could d e m o n s t r a t e , in k i t t e n s m o n o c u l a r l y d e p r i v e d of vision from bib%h, m a r k e d at~'ophic changes in t h e layers of l a t e r a l g e n i c u l a t e nuclei receiving i n p u t f r o m the closed eye. These m o r p h o l o g i c a l changes were less e v i d e n t in k i t t e n s d e p r i v e d a t later ages a n d could n o t b¢ p r o d u c e d in t h e a d u l t cat. No st~tmtural changes could be d e m o n s t r a t e d b y "Wiesel a n d H u b e l (1963a) in the r e t i n a a n d t h e v i s u a l cortex, t h o u g h some a b n o r m a l i t i e s of r e t i n a l ganglion cells follox~/ng lightd e p r i v a t i o n were r e p o r t e d b y Brattg~trd (]952) i n t h e r a b b i t a n d b y 1-¢asch, Swift, t~iesen a n d Chow (1961) in t h e c]fimpanzee, c a t a n d rat; these changes included a decrease of celhflar p r o t e i n s a n d of c y t o p l a s m i c and nucleolar ribonucleie acid. Minor electrophysiological a b n o r m a l i t i e s were recorded b y ~Viesel a n d ]:Iubel (1963a) i t t h e l a t e r a l g e n i c u l a t e nucleus of k i t t e n s m o n o c u l a r l y d e p r i v e d of vision; on t h e o t h e r h a n d , single m~.it recordings from t h e s t r i a t e cortex in these a n i m a l s showed tmresponsiveness of cortical cells to s t i m u l a t i o n of the d e p r i v e d eye ('Wiesel a n d I-Iubel, I963b). D y n a m i c m e t a b o l i c i n v e s t i g a t i o n s in these e x p e r i m e n t a l conditions are still lackhlg, with t h e e x c e p t i o n of a p r e l i m i n a r y r e p o r t from this l a b o r a t o r y (Maraini, Franguelti, :Pasiuo a n d D i o t t i , 1963); i t ;vas therefore considered of i n t e r e s t to s t u d y t h e effect of m o n o c u l a r l i g h t d e p r i v a t i o n on some m e t a b o l i c a c t i v i t y of t h e cells of t h e r e t i n a a n d o f t h e o p t i c centres. Since several i n v e s t i g a t o r s (]3rattgi~rd, H y d d n a n d S j 6 s t r a n d , 1958; A]tm.an, 1963; ~Vat~uon, 1965) r e p o r t e d a tfigher u t i l i z a t i o n of a m i n o acids i~ nerve cells du~'ing increased a c t i v i t y , t h e autoradio~cq'aplfic e v a l u a t i o n of DL-[aH] leucine i n c o r p o r a t i o n was utilized to s t u d y p r o t e i n m e t a b o l i s m in the r e t i n a , lateral geniculate nucleus a n d s t r i a t e cortex of r a t s d e p r i v e d of vision in one eye since t h e end of t h e second week of life. I n t h e r a t o~ly t h e optic fibres coming f r o m t h e e x t r e m e t e m p o r a l r e t i n a go to t h e ~mcro~ed l a t e r a l g e n i c u l a t e nucleus; t h e r e m a h f i n g b p t i c fibres p r o b a b l y all decussate (Laslfiey, 1934.). E v i d e n c e is a v a i l a b l e for t h e t e r m i n a t i o n of t h e uncrossed fibres o n l y in t h e posterior h a l f of t h e m e d i a n p o r t i o n of t h e nucleus. 299
300
G. M A R A ] N ' I ,
F. CAR:I'A,
R. ~'RANGUELLI
AND
5I. S A N T O R I
2. M a t e r i a l s and M e t h o d s
Monocular light-deprivation was obtained in newborn Wistar rats (14-days-old) by suturing together the lids of the right cyc for different periods of time (,t-7 months). This method was shown (~-Vieseland Hubel, 1963a) to completely prevent form stimulation and also stimulation by diffuse light. DL-[aH]Leucine was injected intravcnously ('d.)out 70/zc/100 g wt) and the animals were killed by exsanguination under ethcr anesthesia after 1-5 hr. After immediate fixation in Carnoy's solution sections (4-/z) of the eyes and brain were prepared for autoradiography; in the brain frontal sections were cut through the lateral geniculate nuclei and through the visual cortex. A£ter an adequate period• of expostu-e ('~t 4°C) the slides wero developed and stained with hematoxylin and eosin or with cresyl violet. 3. R e s u l t s and D i s c u s s i o n
The results of the grab~ comlts on t h e different r e t i n a l layers, on the n e u r o n s of l a t e r a l g e n i c u l a t e nuclei, a n d of t h e different layers of t h e ~dsual cortex are reported in t h e tables. No gross morphological differences were observed b e t w e e n t h e n o r m a l and lightd e p r i v e d retinas, and between r i g h t a n d left visual cortex.
TABLE I
Incorporation of [3It]leu~ine in the retina of normal a,n~I visual deprived eyes
R o d s layer Outer nuclear layer •O u t e r p l c x i f o r m l a y e r I n n e r nucl ear l a y e r Inner plexiform layer Ganglion cells
R i g h t eye
Left eye
4-204-1-86 3"91~= 1.62 6-804-6.46 4-62_4= 1" 74 3-50 4-1.57 9.644-7-47
4 - 3 8 " : l "97 3.72_J: 1-20 6-8 l ~: 6-36 5"25 _-i:1.95 4-17 ~_ 2-07 10-35-:_L8-80
Values o f t h e m e a n g r a i n c o u n t s (5 animals) c o r r e c t e d for a surface u n i t o f 100/~*
Correspondingly, leucine i n c o r p o r a t i o n showed no significant modifications hx t h e different r e t i n a l layers of t h e n o r m a l a n d of t h e l i g h t - d e p r i v e d eye (Table I); t h e same was recorded for t h e differe_nt layers of r i g h t a n d left v i s u a l cortex (Table II). On t h e c o n t r a r y , a small b u t c o n s t a n t decrease of t h e u p t a k e was d e t e c t e d iu t h e g a n g l i o n cells of t h e l a t e r a l g e n i c u l a t e nucleus receiving i n p u t f r o m t h e closed eye (Table I I I ) . S t a t i s t i c a l e v a l u a t i o n showed t h a t this difference was h i g h l y significant (t, for paired compa~!sons -- 5-2437; P ~ 0 - 0 1 ) . The m e a n cellular surface on sections i n c l u d i n g t h e nucleohm was t h e n d e t e r m i n e d on 50 n e u r o n s in s y m m e t r i c a l areas of t h e dorsal p a r t of l a t e r a l geniculate nuclei (a p l a n i m e t r i c device was utilized on h i g h m a g n i f i c a t i o n microphotogTap]m). A decrease of a b o u t 2 0 % of cellular surface was d e t e c t e d in t h e ganglion cells of t h e left l a t e r a l g e n i c u l a t e nucleus (t .= 5-4406;
P
T• I l E
I/,ETINA
.'\NI)
el'TIC
'
C E N " ' [ I ,". E 'S
OF
TIIE
NEW]~OR.N
1LAq:
301
Monocular light-depriwttion in newborn rats, short;ly after the period of n.ornnd eye opening, therefore produces a significanl~ decrease of amino acid incorporation in the ztcurons of the lateral genieulatc mtcleus connected with the closed eye; a fairly good parallelism seems, moreow;r, to exist in t.he same ('ells between the decrease of Ieucine uptake and the decrease of cellular surface. ]3y confirming the morphological results obtained in the cat by Wicsel and l:iubel (1963a) and by adding some new Tam.~ .[.[
I.nco.,Toration of [all]leucine in the neurons of the d'iffe~'ent layers of the visual cortex Rat nO,
1 * ." . 3 4
2rid a n d 3rd l a y e r l{ L
9'6 :!. 2-4 9'2":2"2 . 2"0 . 4. ' 0 ; . 2"0 . 4'0-:
4th layer
5th la.yer
6th layer
lg
L
I¢
L
R
L
6"I .!:3"4 . 4"3-;-2"8 . . 4"0:" 3"0 ,t"4-= 2"S
5"9.i:3" 1 . . 4"0.:.2"4 3"8 :!: 2"6 4"5-:- 2"6
18"9::: 7"3 ] 1"5 :.--t'3 9" 6 -2"5"0 11"5=.~4"3
I8"2='.=6"5 12"7:k5"S ,'1-9 5=6"0 1°"2 J-4"2
14"5=/:5"6 . ;.o ~ o."~,1..:=3 4"8 --- 2" 7 5"9-;--3"2
I3"44=6"9 5"2 " : 2 " 8 5" 7 -'= 2"9 5"2 -i2"8
A t l e a s t 2(1{) cells w e r e c o u n t e d in e a c h l a y e r t o dc, t e r m i n e m e a n g r a i n c o u n t , * G r a i n c o u n t s t b r 6th. h w e r w e r e d o n e o n l y on coils c u t in t h e p l a n e o f t h e i r nueleoli.
T:uml.: I I I
I.ncorporalix)n of [~H]leucinc in the .neurons of lat.eral genic ulate .~vuclei Rat m,.
1
2 3 4 5
Right
Left
Months of deprivation
16"39-k. 6"83 6.26--: 2-19 8.5{I :!" 4-00 8.59 -2:3-90 10.12 ,-3"95
14.16:~ 10.95 5"04 =k 1 "38 7.58-i_ 3-58 5" 7 0 ~ 2' 70 8.48..'=3.81
7 4 4 4 4
F r o n t a l s e c t i o n s were c u t t h r o u g h t h e d o r s a l p a r t o f l a t e r a l g e n i c u l a t e nuclei; a t l e a s t 200 cells w e r e c o u n t e d t o d e t e r m i n e t h e mea~a a m o u n t o f labelling. A n o r m a l d i s t r i b u t i o n w a s d e t e c t e d in t h e ceil pop~flations b o t h of r i g h t anti l e f t nuclei.
metabolic data, the present experiment t;herefore brings further support to the generalization that, following monocular light-deprivation, the most obvious changes seem to occur, wittfin the visual system, at the level of the lateral geniculate nucleus. These findings may be of some help in the interpretation of the functional arnblyopia that follows some similar clinical situations, as for example congenital cataracts.
302
(';. g I A I l A I N I ,
1~'. CAH,'I:A, It. I.'It, ANGUI,ILI,! A N D 3I. 8 A N T O I t l I'~ 1~ le l~' R l~',N (J E 8
Altm~m, O. (1963). N , ture 199, 777. Brat, tg?~rd, S. O. (1952). Act,t l~adiol., ,%l,pl. 96, 1. zh'attgtLz'd, S. O., lt'yd6n, ]-1. ~md Sj6strand, ,I. (1958), N , t nre 182, 801. I,ashl~y, K. S. (1934). 3. (Jomp, Neural. 59, :141. •~13raini, G., li'r~mguelli, J~,, l.)~tsino, ]]. ~md ])iotA,i, (I. (196"1), lloll. Oc:uli,~t. 42, 175. ltasclh I:]., Swift~, IL, ] tie.sen, A. I f, mM Oho w, l~. l,, ( 196 l). £:rpll Cell Res. 25, :1,18. W~tson, W. Jig. (1965). 0ri Phlt,~iol. (Londot~) 180, 754. Wiesol, 'J:. N. and 1! ubel, ]). I[. (1963~.), 3. Neuroph#,~iol. 26, 978. Wiesel, 'P. N. and llul)el, l). 1"1, (1963b). ,1, Ne~trophysiol. 26, 1003. Wiesel, 'P. N, and H,bel, D. 1[. (1965). 3. Neu,rophysiol. 28, l()tI0, If
O
-,
Effect o f M o n o c u l a r Light-deprivation on L e u c i n e U p t a k e in the R e t i n a and the O p t i c Centres o f the N e w b o r n R a t G. MARAINI, 1~'. CAR'rA, n . , FRANGUELLI AND ~I. SA2~TORI University Eye Clinic, University of Parma, Italy (Received 20 March 1967, London) Monocular light.deprivation"irrno~vbornrats, shortly after the period of normal eye opening, produces a significant decrease of [aH]lcuoine incorporation, and of cellular surface, in the ncurolm of the lat.eral geniculate nucleus connected with the closed eye. No modification of amino acid uptake was detected in the different cellular layers of the retina and of the visual cortex. 1. I n t r o d u c t i o n
The i m p o r t a n c e of a n o r m a l sensory s t i m u l a t i o n on t h e d e v e l o p m e n t and f u n c t i o n a l efficiency of t h e eye a n d of t h e optic ccntres is now g e n e r a l l y a d m i t t e d a n d has r e c e n t l y been stressed b y t h e i m p o r t a n t c o n t r i b u t i o n s of Wiesel a n d ]=Iubel (1963a,b, 1965). These a u t h o r s could d e m o n s t r a t e , in k i t t e n s m o n o c u l a r l y d e p r i v e d of vision from bib%h, m a r k e d at~'ophic changes in t h e layers of l a t e r a l g e n i c u l a t e nuclei receiving i n p u t f r o m the closed eye. These m o r p h o l o g i c a l changes were less e v i d e n t in k i t t e n s d e p r i v e d a t later ages a n d could n o t b¢ p r o d u c e d in t h e a d u l t cat. No st~tmtural changes could be d e m o n s t r a t e d b y "Wiesel a n d H u b e l (1963a) in the r e t i n a a n d t h e v i s u a l cortex, t h o u g h some a b n o r m a l i t i e s of r e t i n a l ganglion cells follox~/ng lightd e p r i v a t i o n were r e p o r t e d b y Brattg~trd (]952) i n t h e r a b b i t a n d b y 1-¢asch, Swift, t~iesen a n d Chow (1961) in t h e c]fimpanzee, c a t a n d rat; these changes included a decrease of celhflar p r o t e i n s a n d of c y t o p l a s m i c and nucleolar ribonucleie acid. Minor electrophysiological a b n o r m a l i t i e s were recorded b y ~Viesel a n d ]:Iubel (1963a) i t t h e l a t e r a l g e n i c u l a t e nucleus of k i t t e n s m o n o c u l a r l y d e p r i v e d of vision; on t h e o t h e r h a n d , single m~.it recordings from t h e s t r i a t e cortex in these a n i m a l s showed tmresponsiveness of cortical cells to s t i m u l a t i o n of the d e p r i v e d eye ('Wiesel a n d I-Iubel, I963b). D y n a m i c m e t a b o l i c i n v e s t i g a t i o n s in these e x p e r i m e n t a l conditions are still lackhlg, with t h e e x c e p t i o n of a p r e l i m i n a r y r e p o r t from this l a b o r a t o r y (Maraini, Franguelti, :Pasiuo a n d D i o t t i , 1963); i t ;vas therefore considered of i n t e r e s t to s t u d y t h e effect of m o n o c u l a r l i g h t d e p r i v a t i o n on some m e t a b o l i c a c t i v i t y of t h e cells of t h e r e t i n a a n d o f t h e o p t i c centres. Since several i n v e s t i g a t o r s (]3rattgi~rd, H y d d n a n d S j 6 s t r a n d , 1958; A]tm.an, 1963; ~Vat~uon, 1965) r e p o r t e d a tfigher u t i l i z a t i o n of a m i n o acids i~ nerve cells du~'ing increased a c t i v i t y , t h e autoradio~cq'aplfic e v a l u a t i o n of DL-[aH] leucine i n c o r p o r a t i o n was utilized to s t u d y p r o t e i n m e t a b o l i s m in the r e t i n a , lateral geniculate nucleus a n d s t r i a t e cortex of r a t s d e p r i v e d of vision in one eye since t h e end of t h e second week of life. I n t h e r a t o~ly t h e optic fibres coming f r o m t h e e x t r e m e t e m p o r a l r e t i n a go to t h e ~mcro~ed l a t e r a l g e n i c u l a t e nucleus; t h e r e m a h f i n g b p t i c fibres p r o b a b l y all decussate (Laslfiey, 1934.). E v i d e n c e is a v a i l a b l e for t h e t e r m i n a t i o n of t h e uncrossed fibres o n l y in t h e posterior h a l f of t h e m e d i a n p o r t i o n of t h e nucleus. 299
300
G. M A R A ] N ' I ,
F. CAR:I'A,
R. ~'RANGUELLI
AND
5I. S A N T O R I
2. M a t e r i a l s and M e t h o d s
Monocular light-deprivation was obtained in newborn Wistar rats (14-days-old) by suturing together the lids of the right cyc for different periods of time (,t-7 months). This method was shown (~-Vieseland Hubel, 1963a) to completely prevent form stimulation and also stimulation by diffuse light. DL-[aH]Leucine was injected intravcnously ('d.)out 70/zc/100 g wt) and the animals were killed by exsanguination under ethcr anesthesia after 1-5 hr. After immediate fixation in Carnoy's solution sections (4-/z) of the eyes and brain were prepared for autoradiography; in the brain frontal sections were cut through the lateral geniculate nuclei and through the visual cortex. A£ter an adequate period• of expostu-e ('~t 4°C) the slides wero developed and stained with hematoxylin and eosin or with cresyl violet. 3. R e s u l t s and D i s c u s s i o n
The results of the grab~ comlts on t h e different r e t i n a l layers, on the n e u r o n s of l a t e r a l g e n i c u l a t e nuclei, a n d of t h e different layers of t h e ~dsual cortex are reported in t h e tables. No gross morphological differences were observed b e t w e e n t h e n o r m a l and lightd e p r i v e d retinas, and between r i g h t a n d left visual cortex.
TABLE I
Incorporation of [3It]leu~ine in the retina of normal a,n~I visual deprived eyes
R o d s layer Outer nuclear layer •O u t e r p l c x i f o r m l a y e r I n n e r nucl ear l a y e r Inner plexiform layer Ganglion cells
R i g h t eye
Left eye
4-204-1-86 3"91~= 1.62 6-804-6.46 4-62_4= 1" 74 3-50 4-1.57 9.644-7-47
4 - 3 8 " : l "97 3.72_J: 1-20 6-8 l ~: 6-36 5"25 _-i:1.95 4-17 ~_ 2-07 10-35-:_L8-80
Values o f t h e m e a n g r a i n c o u n t s (5 animals) c o r r e c t e d for a surface u n i t o f 100/~*
Correspondingly, leucine i n c o r p o r a t i o n showed no significant modifications hx t h e different r e t i n a l layers of t h e n o r m a l a n d of t h e l i g h t - d e p r i v e d eye (Table I); t h e same was recorded for t h e differe_nt layers of r i g h t a n d left v i s u a l cortex (Table II). On t h e c o n t r a r y , a small b u t c o n s t a n t decrease of t h e u p t a k e was d e t e c t e d iu t h e g a n g l i o n cells of t h e l a t e r a l g e n i c u l a t e nucleus receiving i n p u t f r o m t h e closed eye (Table I I I ) . S t a t i s t i c a l e v a l u a t i o n showed t h a t this difference was h i g h l y significant (t, for paired compa~!sons -- 5-2437; P ~ 0 - 0 1 ) . The m e a n cellular surface on sections i n c l u d i n g t h e nucleohm was t h e n d e t e r m i n e d on 50 n e u r o n s in s y m m e t r i c a l areas of t h e dorsal p a r t of l a t e r a l geniculate nuclei (a p l a n i m e t r i c device was utilized on h i g h m a g n i f i c a t i o n microphotogTap]m). A decrease of a b o u t 2 0 % of cellular surface was d e t e c t e d in t h e ganglion cells of t h e left l a t e r a l g e n i c u l a t e nucleus (t .= 5-4406;
P
T• I l E
I/,ETINA
.'\NI)
el'TIC
'
C E N " ' [ I ,". E 'S
OF
TIIE
NEW]~OR.N
1LAq:
301
Monocular light-depriwttion in newborn rats, short;ly after the period of n.ornnd eye opening, therefore produces a significanl~ decrease of amino acid incorporation in the ztcurons of the lateral genieulatc mtcleus connected with the closed eye; a fairly good parallelism seems, moreow;r, to exist in t.he same ('ells between the decrease of Ieucine uptake and the decrease of cellular surface. ]3y confirming the morphological results obtained in the cat by Wicsel and l:iubel (1963a) and by adding some new Tam.~ .[.[
I.nco.,Toration of [all]leucine in the neurons of the d'iffe~'ent layers of the visual cortex Rat nO,
1 * ." . 3 4
2rid a n d 3rd l a y e r l{ L
9'6 :!. 2-4 9'2":2"2 . 2"0 . 4. ' 0 ; . 2"0 . 4'0-:
4th layer
5th la.yer
6th layer
lg
L
I¢
L
R
L
6"I .!:3"4 . 4"3-;-2"8 . . 4"0:" 3"0 ,t"4-= 2"S
5"9.i:3" 1 . . 4"0.:.2"4 3"8 :!: 2"6 4"5-:- 2"6
18"9::: 7"3 ] 1"5 :.--t'3 9" 6 -2"5"0 11"5=.~4"3
I8"2='.=6"5 12"7:k5"S ,'1-9 5=6"0 1°"2 J-4"2
14"5=/:5"6 . ;.o ~ o."~,1..:=3 4"8 --- 2" 7 5"9-;--3"2
I3"44=6"9 5"2 " : 2 " 8 5" 7 -'= 2"9 5"2 -i2"8
A t l e a s t 2(1{) cells w e r e c o u n t e d in e a c h l a y e r t o dc, t e r m i n e m e a n g r a i n c o u n t , * G r a i n c o u n t s t b r 6th. h w e r w e r e d o n e o n l y on coils c u t in t h e p l a n e o f t h e i r nueleoli.
T:uml.: I I I
I.ncorporalix)n of [~H]leucinc in the .neurons of lat.eral genic ulate .~vuclei Rat m,.
1
2 3 4 5
Right
Left
Months of deprivation
16"39-k. 6"83 6.26--: 2-19 8.5{I :!" 4-00 8.59 -2:3-90 10.12 ,-3"95
14.16:~ 10.95 5"04 =k 1 "38 7.58-i_ 3-58 5" 7 0 ~ 2' 70 8.48..'=3.81
7 4 4 4 4
F r o n t a l s e c t i o n s were c u t t h r o u g h t h e d o r s a l p a r t o f l a t e r a l g e n i c u l a t e nuclei; a t l e a s t 200 cells w e r e c o u n t e d t o d e t e r m i n e t h e mea~a a m o u n t o f labelling. A n o r m a l d i s t r i b u t i o n w a s d e t e c t e d in t h e ceil pop~flations b o t h of r i g h t anti l e f t nuclei.
metabolic data, the present experiment t;herefore brings further support to the generalization that, following monocular light-deprivation, the most obvious changes seem to occur, wittfin the visual system, at the level of the lateral geniculate nucleus. These findings may be of some help in the interpretation of the functional arnblyopia that follows some similar clinical situations, as for example congenital cataracts.
302
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Altm~m, O. (1963). N , ture 199, 777. Brat, tg?~rd, S. O. (1952). Act,t l~adiol., ,%l,pl. 96, 1. zh'attgtLz'd, S. O., lt'yd6n, ]-1. ~md Sj6strand, ,I. (1958), N , t nre 182, 801. I,ashl~y, K. S. (1934). 3. (Jomp, Neural. 59, :141. •~13raini, G., li'r~mguelli, J~,, l.)~tsino, ]]. ~md ])iotA,i, (I. (196"1), lloll. Oc:uli,~t. 42, 175. ltasclh I:]., Swift~, IL, ] tie.sen, A. I f, mM Oho w, l~. l,, ( 196 l). £:rpll Cell Res. 25, :1,18. W~tson, W. Jig. (1965). 0ri Phlt,~iol. (Londot~) 180, 754. Wiesol, 'J:. N. and 1! ubel, ]). I[. (1963~.), 3. Neuroph#,~iol. 26, 978. Wiesel, 'P. N. and llul)el, l). 1"1, (1963b). ,1, Ne~trophysiol. 26, 1003. Wiesel, 'P. N, and H,bel, D. 1[. (1965). 3. Neu,rophysiol. 28, l()tI0, If
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