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Differential roles of cerebellar cortex and deep cerebellar nuclei in the learning of the equilibrium behavior: studies in intact and cerebellectomized lurcher mutant mice
ELSEVIER
Developmental Bran Research 66 (1995) 31 I-316
Research
report
Differential roles of cerebellar cortex and deep cerebellar nuclei in the learning of the equilibrium behavior: studies in intact and cerebellectomized lurcher mutant mice
Abstract
Three- to 6-month-old lurcher mutant mice (+ /ICI, which exhtbu a masswe loss of neurons in the cerebellar wrtex and in the inferior oliiary nucleus but whose deep cerebellar nuclei are essentially mtact. were trained daily, for 9 days, to maintain their equilibrium upon a rota rod rotating at 20 or 30 revolutions per minute (rpm). Theu scores were measured and their behavior upon the rotating rod quantified in comparison to those of matched control mice. Lurcher mice were able to learn to maintain their equilibrium eKGently when rotated at 20 rpm but were not when rotated at 30 rpm. After cerebeliectomy, the equilibrium capabilities of the animals were much altered, especially in + /lc. Thrse results show that the deep CerebeUar nuclei are sufficient for motor learning, provided the task is not too difficult (20 rpm), but that the cerebellar cortex is required when the task is more difficult (30 rpm). Therefore, it can be concluded that the adaprw motor capabilities of lurcher mice are less developped than those of con:rol animals.
(+/ L)
Keywords: Lurcher; Mutant mouse: Cerebellum;
Equilibrium; Motor leatnmg --
1. IntmduetIon From a number of studies, it is known that the cerebellum is involved in the storage of motor programs and in complex sensorimotor coordinations. The moat currently accepted models of cerebellar learning are based on the differential role of climbing and parallel fibers inputs in the conditioning of motor responses [1,8,10,15]. In all these models, the cerebellar cortex is consider4 to be the main site of motor learning: the Purkinje cells wouid ‘learn’ to respond to parallel fiber input only if they were previously coactivated by both climbing and parallel fibers. In keeping with this assumption, it has been demonstrated that there is a correlation between the activity of many Purkinje cells and the classical conditioning of the nictitating membrane response to an auditory stimulus
* Corresponding author. Fax: (33) 35.14.63.49. 0165-3806/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDI 0165~3@06!95!00037-2
[3], and that lesions of the cerebe-l!ar cortex abolish the response and prevent it to being learned again [21]. However, this interpretation has been questioned, and studies are not rare which demonstrate that the cerebellar cortex is not necessary for this conditioning, whereas the deep nuclei [13,16,18,19], inferior olivary complex [17] and pontine nuclei [71 are needed. Finally, it has been shown that both the cerebellar cortex and deep nuclei are needed for the acquisition of more complex behzwor such .+s eqG%&m~ in yueog rats [2,221. The adult lurcher mutant mouse offers the opportunity to discriminate the respective participation of the cerebellar cortex and deep cerebellar nuclei in learning of motor skills. !n the heterozygous ( + /ICI mutant, all the Purkinje ceils (whose axons represent the ordy output of the cortex) and &St all the granule cells have degenerated in the cerebellar cortex, whereas the deep nuclei remain essentially intact [S] or exhibit mild degeneration. According to Heckroth 191, while the
1. Castonnal./Lk~alBmin
312
cerebeUar nuclei reveal an overall 60% decrease in volume, cell counts show that the principal neurons are only slightly reduced in number (-20%) and that the population of small neurons which is reduced by 37% in the interposed and dentate nuclei is unchanged in the fastigial nucleus. Therefore, the present investigation was aimed as studying the acquisition of the equibium behavior in adult lurcher mutant mice. For this plrposc, the scores of lurcher ( + /Ic) and control mice (+/+ ) were studied and compared in a 6rst set of experiments. The same study was then performed in cc&eUectomixed + / + and + /Ic; scores obtained in intact and in cerebellectomixed +/lc were compared in order to disclose the possible role of deep nuclei in motor leaming. Scores of cerebellectomized controls and mutants were also compared to study whether the lack of cerebellum exerts a similar effect on the acquisition of the equiUirium behavior. 2. Materials and metbeds 21. A?limaf!s Lurcher (+/ICI mice of the MCBA strain and control (+ / + ) mice of the same strain were obtained from our breeding colony maintained at the Institut Gustave Roussy (ViUejuif). They were 3-6-month-old at the begimrbrg of the experiments and were reared in standard conditions (12 h tight-12 h dark, 20-WC, food and water ad hi.). Inafirstsetofexpcrimettts,8 +/lcandlO +/+ mice were studied. In a second set of experiments, the same study was performed in 6 +/lc and 10 +/ + mice in which complete cerebcllectomy was successful. 2.2. Eqxrimmtal device The device used was a rota rod similar to the one used in our previous studies [2,6,22].It consisted of a horizontalwood mast (3 cm in diameter, 40 cm lone) covered with sticking plaster in order to increase roughness; rotation around its longitudinal axis was driver by a DC electric motor, the rotation rates were 20 anI 30 revolutions per minute (rpm). A landing platfor u covered with a thick sheet of soft plastic was placed 5 cm under the rod to cushion the fall of the animals. 23. Ex@mentaI
ptxidlm
All the animals, whether controls or mutants, were subjected daily to a series of 10 trials, the time interval between two successive trials never beii shorter than 2 min. Each trial was performed in the following way: the mouse was placed upon the rod while it was
Rrscrrnh86 (1995)311-316
already rotating, its body axis being perpendicular to the rotation axis at the onset of the trial; the head was directed against the direction of the rotation so that the anhttai had to progress forward to maintain its balance. Retween trials, the animals were returned to their cage; they were easily distingutthed by different patterns of permanent colo~rrcdma&s painted on their tail. Quantitative and behavioral data were coilected. Mean sore*: the time during which the animals stayed upon the rota rod without falling down was measured (the chronometer was released when the mouse was placed upon the rota rod and stopped when it feU down). According to previous studies [2,6,22],the maximal score was arbitrarily fixed to 3 min sinewit has been shown that young rats [2] as well as adult mice [6] which maintain their equilibrium for 3 min are able to maintain it for a much longer time (M-20 min, sometimes more). The experimentwas stopped either when the mouse reached the maximal 3 min score at each of the 10 trials of a series, or, for the few animals which could not reach this maximal score, the 9th day after the begimlling of training. Behavioral profiles consisted in observing the be.havior of the animals when rotated, that is the strategy (grasping or walking)they used to maintain their equilibrium. The relative proportions of these patterns were calculated. The animals were first rotated at 20 rpm, and 2 weeks after this experiment ended, at 30 rpm. 2.4. Dnta anal@ For each animal and for each rotation rate, the scores of the 10 trials were averaged in order to get the mean daily score (ml Then, the mean daily score W) obtained by the n animals of each group was calculated W = Zm/n) f S.E.M. (o/&rin).Useful intergroup comparisons were made according to ANOVA. From the behavioraldata noted every 10 seconds it was possible to quantifythe percentageof each activity (graspingand walking)duringeach trial. Fit, for each animal, and then for each group, mean daily pcrcentages and cumulated percentages during the 9 days of training were calculated. Percentage intergroup comparisons were made with X’ test. 2.5. Cerebdectomv Fiieen +/+ and 10 +/Ic mice with no prelesion training were cerebeUe.ctomixed after being anesthetized by an i.p. injection of chloral hydrate (250 mg . kg-‘). The mice were secured in a stereotaxic apparatus,the skin of the skull incised, the neck muscles cut, the occipital bone drilled and removed. After .Wting the dura, care being taken to avoid bleeding, the cerebellum (cortex and deep nuclei) was removed
by suction and the cavity filled with Gelfoam. the skin was sutured and the animals allowed cover during 1 week before testing.
Then, to re-
2.6. Control of the operation After completion of the behavioral studies, the cerebellectomized mice were given an overdose of pentobarbital sodium and perfused intracardially with a mixture of 4% rraraformaldehyde and 0.3% glutaraidehyde in phosphate buffer. The brains were removed and placed in 10% formalin for about 10 days. Ah the brains were carefully examined under the di setting microscope in order to estimate the extent of the lesion. From the 25 brains examined, 9 were discarded because of partial or wrong lesions. Among the 16 remaining brains (10 belonging to the + / + group and 6 to the + /Ic group), 8 (5 in the + / + group and 3 in the +/ic group) were prepared tar histology. Frozen sections, 20 pm thick, were stained with Cresyi vioier and examined under a light microscope.
3. Resuits 3.1. Non-cerebellectomi
animals
3.1.1. Control anirnuk During the first day of training, all the 10 + / + mice studied reached the fixed criterion of 180 s, that is thq maintained their equilibrium upon the rotating rod for at least 180 s at each of the 10 trials of the
20
c
0i
.. 2orpm
20
+,x rpm
.,.
Cb 20 rpm
.,lc 3orpm
.,lE
Cb
20 rpm
Fig 2. Cwulated percentages(*S.&.M.) of the dierent behavioral sequenceson the rota rod during the training session;a: + / + mice tramedat2Orpm.b +/+ mketminedrt.%rpm:c: +/krnke tramed at 20 rpm: d. + mice hained at 30 rpm; e: cerebeltectomized + / + macetrained at 20 t-pm; f: cercbelto%nnized +/tic m!cr tramed a! ?O .qtn. Full ban: grarping behavior empty ban: :;alkme bebavwr
/k
series, whatever the rotation rate (20 or 30 rpm) (Fig. 1A). From the behavioral profile, it can be observed thai for the rotatron rate of 20 rpm as well as for the rotation rate of 30 rpm, the cumulated percentage of walking was near 100% (%.8% and %.2%, respectively), indicating that the mice used walking atmost all the time to maintain their equihbrium, the walking behavior being well synchronized with the rotation of the rod (Fig. 2a.b).
‘30 A
150 1
cb-
+,t
20rpm
0 *I lc Cb- 20 rpm 140-
: : T TI A-
:
7
,
&‘-
,b-4
:
4
i-h,
_A,
40 I_
20 0
1
+I+
20
rpm
.
r/k
20
rpm
and
30
2r I’
rpm
20 .
+,,c
30
rpm
1 2 3 4 5 6-e&l a
I?oys
I
Of
r r
1
tro1mng
1
I
,b-‘J+-b
h-’ o_-o _-L_a__o--6’
0i -1
2
3 Days
4 Of
5
6
7
8
9
tralnlng
Fii. :. Ewlution of the scoresof the animals. in xmnds f S.E.M. (ordinates). when tramed on the rota rod for 9 mnsecutivedaysf~bscissae).A: full triangle: + / + mice trained at 20 md at 30 rpm (for both rotation rates, they reached rhe 180 set fixed m&al score by the first day of training); full circles: + /k macetramed at 20 rprn; full squares:+ /Ic mice trained at Xl rpm. R: open triangles:oerebelkctomized + / + mice trained at 20 rpm; open circles:cmebelkctomized + /k mice trained at 20 rpm.
J. Caston et al /lkceiwmentcu
316
preoperativesensorimotorexperiencewas richer,both quantitatively
and qualitatively,
than that of + /Ic mice.
Thii work was supportedby grantsfrom MRE bxmtract no 92.C.O756),Fondationde la Kecherchem&Iitale, Fondationde France,A.F.M., I.N.S.E.R.M.(CRE no 921105 and 930708),Cites and FiammarionCornpaR&S.We want to thankDan Geslan for housingof the animalsand Ann L.ohoffor reviewingthe English.
iBrainRese,wzh86 (1995)311-316 belkr nocki in oormal and lurchcr mutant mice. I. Morphology and all number, I. Cump.New& 343 (1994) 173-182. I101Ito, M. Synaptic plasticity in the eerebellar cortex that may undcrlk lbc vcstiiiosculu adaptation.In A. Bcrthoz and G. M&ii Jonw GZds.), Ada@iw Mecha&ms in Gore Conrrd Facti and l7semiq Ekcvier, New York, 1985.pp. 213-221. [ill Iwy. R.B. cod Kcele, S.W.. Tiig fimctioos of the cwebclium, 1. Co8nitit.w Ncunx&ncu, lG989) 136-152. 1121Ldondc. R.. Beta. MI., Joyal. C.C. and Caumartin.M., Motor &omuUtks in lureher mutant mice, &v&f. B&u.. 510992) 523-525. I131 Lwond, D.G., Hembrce, T. and Thompson, R.F., Effect of kaiok acid ksiir of the ccrcbelkr ioterposituj m&us on eyelid cooditiooii in the rabbit, BrainRes., 326 (1985)179-182. [141Ubms, R. and Scsaki, K., The functional organization of the olivoecr&cUar syslcm a8 eumincd Ly multiple Purkinje eeli rwordii Eur. 3. N-i., l(1989) 587-602. 051 Mar&D., A theory of ccrcbclkr cortex, J. Physiol..,202 (1%9) 437-470.
of cercbeUat fimction, Math. Biawi., 10 (1971)25-69. 121Away, N., Casroo, J., Rebcr, A. sod St&, T., Role of the cctcbcllum in the ontogcnesiaof the equilibrium bchwior in the young nt: a khvionl SNdy, Bmh Rcs., 505 (1989) 291-301. 131Bcrthkr, M.E. mid Moore, J.W., Ccrcbclkr Pwkbljc au activby n&d to the clucicrlly cooditiooed nictating membrane wspoosc, Eq?. Brain Res., 63 (1986)341-351. (41 Braitcobcrg,V., Is the arcbelkr cortex a bio&g&l clockin the mdkuwnd mngc 1 Bmln f&s., 25 (1%7) 334-346. [5j Caddy, K.W.T. and Biscoc, T.J., Struchwl and quaotitative stodks 011the nomml QH and bucher mutant mow, Phil Tmns. R Lad, 287 (1979) 167-201. i61 Cutoo, J., Del&c-Bouchwd, N. axI Markoi, I., Mnior bchw ior of bcterozygom staggcrcr mutant (+/sgl vcaua oonnal mice (+ / + ) dwiog &ng, E&au. Brain l&s., submitted. [7j Damwd, I.E. amI Moore, J.W., A brain stern region essential for cbss&aUycooditoncd but nol onconditioncd nictating mcmbraoc rcspome, Phjsid B&au., 28 (1982) 1@29-1033. 181Eccks, J.C. An iosbu&m-s&ction theory of karniog in the cercbclkr oxtcx, Bmin Rw., 127(1977) 327-352. 191Hcckmth, J.A., Qoantitativcmorphologicalanalysis of tbc ccrc-
[II Albus, S.S., A lbcoty
..
[161McComdcL DA., Lpwod, D.G., Clark, G.Ak, Kcttwr, R.E., Rismg, CA. lad Tbompsoo, R.F., The engram found? Role of the cercbcllom k cksskal conditioomgof nictitatingmembrane aod yelid rcspoosc, RI& &&OIL Sot.. 18 (1981) 103-105. 117l McCodck, D.A., Ste~wtz, J.E. and Thompson, R.F., Lesions of inferior oliwry compkr cause extinctioo of the classically conditioned eyeblinkresponse, B&n Rx, 359 (1985) 120-130. [181McCoa D.A. and Thompsoo, RF., Neuronal rrsponscs of the rabbit arcbcllum during acquisition and performancesof a classicaIly conditioocd nktaUnp mcmbranc rcsponsc, 1. New rosci., 4 (1984)2811-2822. [191McCormii D.A. and Thompsoo, R.F., Cerebellum: essential involvementio the ckskally cooditioncd eyelid rcsponsc, Sciw ence, 223 (1984) 296-259. 1201PelUonii A. sod Llirw R., Spsee time rcpnsentacion in the brain: the arcb&m aa P prcdii space tbnc metrk tensor, Nwwckmz, 7 (1982) 2949-297Q. [211Yco, C.H., Hmdimao, MS. cod Glkkrteio, M. Dkcmk lesions of the ccrcbcllar cortex aboliih the ckssic& cooditioncd nktatiog mcmbnac rcspoosc in tbc rabbit, &hou. Bmin Res., 13 (1984) 261-266. I221Zion,C., Away, N., CasNn, J., Rebcr, A nod Stek, T., Effects of eer&elkctmny a1 day 15 on the ootogencsis of the cquilibriumbchavior io the nr, Brain Ru., 515 (1990) 104-110.
Developmental Bran Research 66 (1995) 31 I-316
Research
report
Differential roles of cerebellar cortex and deep cerebellar nuclei in the learning of the equilibrium behavior: studies in intact and cerebellectomized lurcher mutant mice
Abstract
Three- to 6-month-old lurcher mutant mice (+ /ICI, which exhtbu a masswe loss of neurons in the cerebellar wrtex and in the inferior oliiary nucleus but whose deep cerebellar nuclei are essentially mtact. were trained daily, for 9 days, to maintain their equilibrium upon a rota rod rotating at 20 or 30 revolutions per minute (rpm). Theu scores were measured and their behavior upon the rotating rod quantified in comparison to those of matched control mice. Lurcher mice were able to learn to maintain their equilibrium eKGently when rotated at 20 rpm but were not when rotated at 30 rpm. After cerebeliectomy, the equilibrium capabilities of the animals were much altered, especially in + /lc. Thrse results show that the deep CerebeUar nuclei are sufficient for motor learning, provided the task is not too difficult (20 rpm), but that the cerebellar cortex is required when the task is more difficult (30 rpm). Therefore, it can be concluded that the adaprw motor capabilities of lurcher mice are less developped than those of con:rol animals.
(+/ L)
Keywords: Lurcher; Mutant mouse: Cerebellum;
Equilibrium; Motor leatnmg --
1. IntmduetIon From a number of studies, it is known that the cerebellum is involved in the storage of motor programs and in complex sensorimotor coordinations. The moat currently accepted models of cerebellar learning are based on the differential role of climbing and parallel fibers inputs in the conditioning of motor responses [1,8,10,15]. In all these models, the cerebellar cortex is consider4 to be the main site of motor learning: the Purkinje cells wouid ‘learn’ to respond to parallel fiber input only if they were previously coactivated by both climbing and parallel fibers. In keeping with this assumption, it has been demonstrated that there is a correlation between the activity of many Purkinje cells and the classical conditioning of the nictitating membrane response to an auditory stimulus
* Corresponding author. Fax: (33) 35.14.63.49. 0165-3806/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDI 0165~3@06!95!00037-2
[3], and that lesions of the cerebe-l!ar cortex abolish the response and prevent it to being learned again [21]. However, this interpretation has been questioned, and studies are not rare which demonstrate that the cerebellar cortex is not necessary for this conditioning, whereas the deep nuclei [13,16,18,19], inferior olivary complex [17] and pontine nuclei [71 are needed. Finally, it has been shown that both the cerebellar cortex and deep nuclei are needed for the acquisition of more complex behzwor such .+s eqG%&m~ in yueog rats [2,221. The adult lurcher mutant mouse offers the opportunity to discriminate the respective participation of the cerebellar cortex and deep cerebellar nuclei in learning of motor skills. !n the heterozygous ( + /ICI mutant, all the Purkinje ceils (whose axons represent the ordy output of the cortex) and &St all the granule cells have degenerated in the cerebellar cortex, whereas the deep nuclei remain essentially intact [S] or exhibit mild degeneration. According to Heckroth 191, while the
1. Castonnal./Lk~alBmin
312
cerebeUar nuclei reveal an overall 60% decrease in volume, cell counts show that the principal neurons are only slightly reduced in number (-20%) and that the population of small neurons which is reduced by 37% in the interposed and dentate nuclei is unchanged in the fastigial nucleus. Therefore, the present investigation was aimed as studying the acquisition of the equibium behavior in adult lurcher mutant mice. For this plrposc, the scores of lurcher ( + /Ic) and control mice (+/+ ) were studied and compared in a 6rst set of experiments. The same study was then performed in cc&eUectomixed + / + and + /Ic; scores obtained in intact and in cerebellectomixed +/lc were compared in order to disclose the possible role of deep nuclei in motor leaming. Scores of cerebellectomized controls and mutants were also compared to study whether the lack of cerebellum exerts a similar effect on the acquisition of the equiUirium behavior. 2. Materials and metbeds 21. A?limaf!s Lurcher (+/ICI mice of the MCBA strain and control (+ / + ) mice of the same strain were obtained from our breeding colony maintained at the Institut Gustave Roussy (ViUejuif). They were 3-6-month-old at the begimrbrg of the experiments and were reared in standard conditions (12 h tight-12 h dark, 20-WC, food and water ad hi.). Inafirstsetofexpcrimettts,8 +/lcandlO +/+ mice were studied. In a second set of experiments, the same study was performed in 6 +/lc and 10 +/ + mice in which complete cerebcllectomy was successful. 2.2. Eqxrimmtal device The device used was a rota rod similar to the one used in our previous studies [2,6,22].It consisted of a horizontalwood mast (3 cm in diameter, 40 cm lone) covered with sticking plaster in order to increase roughness; rotation around its longitudinal axis was driver by a DC electric motor, the rotation rates were 20 anI 30 revolutions per minute (rpm). A landing platfor u covered with a thick sheet of soft plastic was placed 5 cm under the rod to cushion the fall of the animals. 23. Ex@mentaI
ptxidlm
All the animals, whether controls or mutants, were subjected daily to a series of 10 trials, the time interval between two successive trials never beii shorter than 2 min. Each trial was performed in the following way: the mouse was placed upon the rod while it was
Rrscrrnh86 (1995)311-316
already rotating, its body axis being perpendicular to the rotation axis at the onset of the trial; the head was directed against the direction of the rotation so that the anhttai had to progress forward to maintain its balance. Retween trials, the animals were returned to their cage; they were easily distingutthed by different patterns of permanent colo~rrcdma&s painted on their tail. Quantitative and behavioral data were coilected. Mean sore*: the time during which the animals stayed upon the rota rod without falling down was measured (the chronometer was released when the mouse was placed upon the rota rod and stopped when it feU down). According to previous studies [2,6,22],the maximal score was arbitrarily fixed to 3 min sinewit has been shown that young rats [2] as well as adult mice [6] which maintain their equilibrium for 3 min are able to maintain it for a much longer time (M-20 min, sometimes more). The experimentwas stopped either when the mouse reached the maximal 3 min score at each of the 10 trials of a series, or, for the few animals which could not reach this maximal score, the 9th day after the begimlling of training. Behavioral profiles consisted in observing the be.havior of the animals when rotated, that is the strategy (grasping or walking)they used to maintain their equilibrium. The relative proportions of these patterns were calculated. The animals were first rotated at 20 rpm, and 2 weeks after this experiment ended, at 30 rpm. 2.4. Dnta anal@ For each animal and for each rotation rate, the scores of the 10 trials were averaged in order to get the mean daily score (ml Then, the mean daily score W) obtained by the n animals of each group was calculated W = Zm/n) f S.E.M. (o/&rin).Useful intergroup comparisons were made according to ANOVA. From the behavioraldata noted every 10 seconds it was possible to quantifythe percentageof each activity (graspingand walking)duringeach trial. Fit, for each animal, and then for each group, mean daily pcrcentages and cumulated percentages during the 9 days of training were calculated. Percentage intergroup comparisons were made with X’ test. 2.5. Cerebdectomv Fiieen +/+ and 10 +/Ic mice with no prelesion training were cerebeUe.ctomixed after being anesthetized by an i.p. injection of chloral hydrate (250 mg . kg-‘). The mice were secured in a stereotaxic apparatus,the skin of the skull incised, the neck muscles cut, the occipital bone drilled and removed. After .Wting the dura, care being taken to avoid bleeding, the cerebellum (cortex and deep nuclei) was removed
by suction and the cavity filled with Gelfoam. the skin was sutured and the animals allowed cover during 1 week before testing.
Then, to re-
2.6. Control of the operation After completion of the behavioral studies, the cerebellectomized mice were given an overdose of pentobarbital sodium and perfused intracardially with a mixture of 4% rraraformaldehyde and 0.3% glutaraidehyde in phosphate buffer. The brains were removed and placed in 10% formalin for about 10 days. Ah the brains were carefully examined under the di setting microscope in order to estimate the extent of the lesion. From the 25 brains examined, 9 were discarded because of partial or wrong lesions. Among the 16 remaining brains (10 belonging to the + / + group and 6 to the + /Ic group), 8 (5 in the + / + group and 3 in the +/ic group) were prepared tar histology. Frozen sections, 20 pm thick, were stained with Cresyi vioier and examined under a light microscope.
3. Resuits 3.1. Non-cerebellectomi
animals
3.1.1. Control anirnuk During the first day of training, all the 10 + / + mice studied reached the fixed criterion of 180 s, that is thq maintained their equilibrium upon the rotating rod for at least 180 s at each of the 10 trials of the
20
c
0i
.. 2orpm
20
+,x rpm
.,.
Cb 20 rpm
.,lc 3orpm
.,lE
Cb
20 rpm
Fig 2. Cwulated percentages(*S.&.M.) of the dierent behavioral sequenceson the rota rod during the training session;a: + / + mice tramedat2Orpm.b +/+ mketminedrt.%rpm:c: +/krnke tramed at 20 rpm: d. + mice hained at 30 rpm; e: cerebeltectomized + / + macetrained at 20 t-pm; f: cercbelto%nnized +/tic m!cr tramed a! ?O .qtn. Full ban: grarping behavior empty ban: :;alkme bebavwr
/k
series, whatever the rotation rate (20 or 30 rpm) (Fig. 1A). From the behavioral profile, it can be observed thai for the rotatron rate of 20 rpm as well as for the rotation rate of 30 rpm, the cumulated percentage of walking was near 100% (%.8% and %.2%, respectively), indicating that the mice used walking atmost all the time to maintain their equihbrium, the walking behavior being well synchronized with the rotation of the rod (Fig. 2a.b).
‘30 A
150 1
cb-
+,t
20rpm
0 *I lc Cb- 20 rpm 140-
: : T TI A-
:
7
,
&‘-
,b-4
:
4
i-h,
_A,
40 I_
20 0
1
+I+
20
rpm
.
r/k
20
rpm
and
30
2r I’
rpm
20 .
+,,c
30
rpm
1 2 3 4 5 6-e&l a
I?oys
I
Of
r r
1
tro1mng
1
I
,b-‘J+-b
h-’ o_-o _-L_a__o--6’
0i -1
2
3 Days
4 Of
5
6
7
8
9
tralnlng
Fii. :. Ewlution of the scoresof the animals. in xmnds f S.E.M. (ordinates). when tramed on the rota rod for 9 mnsecutivedaysf~bscissae).A: full triangle: + / + mice trained at 20 md at 30 rpm (for both rotation rates, they reached rhe 180 set fixed m&al score by the first day of training); full circles: + /k macetramed at 20 rprn; full squares:+ /Ic mice trained at Xl rpm. R: open triangles:oerebelkctomized + / + mice trained at 20 rpm; open circles:cmebelkctomized + /k mice trained at 20 rpm.
J. Caston et al /lkceiwmentcu
316
preoperativesensorimotorexperiencewas richer,both quantitatively
and qualitatively,
than that of + /Ic mice.
Thii work was supportedby grantsfrom MRE bxmtract no 92.C.O756),Fondationde la Kecherchem&Iitale, Fondationde France,A.F.M., I.N.S.E.R.M.(CRE no 921105 and 930708),Cites and FiammarionCornpaR&S.We want to thankDan Geslan for housingof the animalsand Ann L.ohoffor reviewingthe English.
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