Spatial Cognitive Performance After Chronic Focal Cerebral Ischemia in Rats

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1 Journal of Cerebral Blood Flow and Meabolism 19: The nernaional Sociey for Cerebral Blood Flow and Meabolism Published by Lippinco Williams & Wilkins nc Philadelphia Spaial Cogniive Performance Afer Chronic Focal Cerebral schemia in Ras Fumihiko Y onemori Tohru Yamaguchi Hideki Yamada and * Akira Tamura Cenral Pharmaceuical Research nsiue Japan Tobacco nc Osaka; and *Deparmen of Neurosurgery Teikyo Universiy School of Medicine Tokyo Japan Summary: The auhors invesigaed he impairmen of spaial cogniive performance in ras wih chronic focal cerebral ischemia using he Morris maze and examined he correlaion beween his defici and oher behavioral changes such as sephrough laency in passive avoidance ask and neurologic score or pahologic changes The auhors focused on he relaionship beween he damaged brain region and he affeced spaial learning behavior n hc Morris maze ask a 8 weeks afer he middle cerebral arery (MCA) occlusion escape laency swimming pah lengh and percen ime spen in goal quadran of MCA-occluded ras were impaired which correlaed wih shrinkage of he corex involving parieal corex bu no caudae-puamen (CP) Middle cerebral arery-occluded ras were also impaired in he percen ime spen in he ouermos annulus and in urning raio which significanly correlaed wih shrinkage of CP bu no corex Middle cerebral arery-occluded ras showed wo ypical search paerns; one was almos he same as ha of sham-operaed and inac ras and he oher was round shaped and had less urning behavior Boh subgroups of MCA- occluded ras divided by urning raio had significanly impaired spaial cogniive performance which indicaes ha he changes of search paern did no affec cogniive performance in he Morris maze The neurologic deficis recovered gradually afer MCA occlusion which correlaed wih shrinkage of corex and CPo The sep-hrough laency in passive avoidance ask of he MCA-occluded ras was impaired bu did no correlae wih shrinkage of corex or CPo These resuls sugges ha he long-erm spaial cogniive defici of MCA-occluded ras is in par associaed wih damage o he corex involving parieal corex and ha he change of search sraegies is associaed wih damage o CPo These findings suppor he idea ha differen brain regions conribue differenly o cogniive performance search sraegies avoidance ask and neurologic performance and may be useful for esimaing he relaed region of funcional disorder in he clinical siuaion Key Words: Focal cerebral ischemia-middle cerebral arery occlusion Morris maze-passive avoidance-neurologic examinaion Search sraegy Paiens wih cerebrovascular disease may exhibi cogniive disurbances such as amnesia and opographic disorienaion as well as neurologic sympoms (Caplan e a ) To sudy he pahophysiology of such sympoms and develop an effecive drug herapy i is necessary o esablish a chronic animal model characerize i using several parameers and esimae he relaed brain regions of funcional disorders The middle cerebral arery (MCA) occlusion model in ras developed by Tamura e al (Tamura e a 1981a 1981b; Yamamoo e a 1988) appears o provide a suiable sroke model because i produces a relaively uniform infarc area and behavioral disurbances of learning and Received April ; final revision received Augus ; acceped Augus Address correspondence and reprin requess o Dr Fumihiko Yonemori Cenral Pharmaceuical Research nsiue Japan Tobacco nc - Murasaki-cho Takasuki Osaka Japan Abbreviaions used: ANOV A analysis of variance; CP caudaepuamen; MCA middle cerebral arery memory can be assessed using acive and passive avoidance asks (Hirakawa e a 1994; Yamamoo e a 1989a 1989b) radial maze (Okada e a 1995b) and Morris maze asks (Markgraf e a 1992; Yonemori e a 1996; Smih e a 1997) in addiion o neurologic deficis (Robinson 1979; Tamura e a 1985; Yamamoo e a 1988; Person e a 1989) is imporan o sudy he relaionship beween infarced region and funcional deficis o esimae he relaed brain regions of he defici afer MCA occlusion We previously repored ha acive avoidance reenion laency bu no passive avoidance laency correlaes wih corical infarc volume (Tamura e a 1993) and furhermore ha in ras rained preoperaively reenion of he Morris maze ask correlaed wih brain infarc volume in MCA-occluded ras (Yonemori e a 1996) Precise and sysemaic sudies using brain-lesioned ras have suggesed ha differen brain regions conribue o spaial cogniive funcions (Thompson 1978; Kolb and Tees 199) However because he damaged area afer 483

2 484 F YONEMOR ET AL MeA occlusion in ras is widely spread i is sill unknown wha areas wihin he region of infarcion are involved in spaial deficis The few sudies ha have focused on his relaionship sugges ha MeA occlusion is capable of producing spaial cogniive disurbance in ras wihou any evidence of neurobiologic damage in he hippocampus (Okada e a 1995a) n his sudy we demonsrae he influence of chronic cerebral infarcion on spaial cogniion as well as on an avoidance ask and neurologic performance in ras and esimae he locaion of he infarced region ha correlaed wih spaial cogniive performance MATERALS AND METHODS Surgical procedure This experimen complied wih he guidelines of animal experimenaion of our laboraories Male Wi sar ras (Sic Shizuoka Japan) aged 1 weeks and weighing 26 o 35 g were anesheized wih 1 % o 2% halohane and he lef MCA was permanenly occluded a a proximal sie (n = 28) wih a microbipolar coagulaor (Tamura e a 1981a; Yamamoo e a 1988) Afer he incision was suured he ras were allowed free access o laboraory chow and waer Sham-operaed ras (n = 19) were subjeced only o exposure of he MCA whereas inac conrol ras (n = 11) underwen no surgery Assessmen of general behavior Neurologic examinaion Sensorimoor performance was evaluaed using a neurologic defici score based on hemiparesis and abnormal posure a and 1 days and and 1 weeks afer surgery The righ hind limb of each ra was exended genly wih round-ipped forceps and he flexor response was evaluaed as (normal) (mild defici) or 2 (severe defici) For assessmen of abnormal posure ras were suspended by he ail; hen forelimb flexion and body wising were evaluaed as (normal) 1 (mild defici) or 2 (severe defici) Toal score was calculaed by adding hemiparesis score and abnormal posure score Locomoor aciviy Sponaneous locomoor aciviy was measured for 9 minues a 7 weeks afer surgery using an auomaed aciviy box (Auo me x ; Columbus nsrumens Columbus OR USA) Passive avoidance ask Ras were esed using a sephrough ype of passive avoidance ask (Yamamoo e a 1988; Jarvik and Kopp 1967) a 7 weeks afer surgery The apparaus (Neuroscience nc Tokyo Japan) consised of wo comparmens: an illuminaed chamber (1 cm x 3 cm) and a dark one (3 cm x 3 cm) The ras iniially underwen habiuaion by being placed in he illuminaed chamber and hen a door beween he chambers was opened so ha hey could ener he dark chamber n he acquisiion rial he ras performed he same ask bu a 6-mA foo shock was delivered hrough he grid floor for second once hey enered he dark chamber Reenion rials were performed wihou foo shock day and 17 days afer he acquisiion rial The sep-hrough laency was recorded o a maximum of 3 seconds Morris maze ask Spaial cogniion was examined using he Morris maze (Morris 1981; Morris e a 1982) A cylindrical ank 144 cm in diameer was filled wih waer o a deph of 32 cm and a ransparen plaform 1 cm in diameer was placed a a fixed posiion in he cener of one of he four quadrans (quadran 2) and he cener of one of he hree annuluses (annulus B) The plaform was se 2 cm below he waer level where he ras could no see i direcly Eigh weeks afer MCA occlusion he ras were allowed o swim freely for minue o become habiuaed From he nex day acquisiion rials were carried ou once a day for 1 days n each rial he ra was placed ino he waer a a fixed saring posiion and he swimming pah o escape ono he hidden plaform was measured using a Video mage Moion Analyzer (AXS3; Neuroscience nc) The ras were given 12 seconds o find he hidden plaform during each acquisiion rial and were allowed o res on he plaform for 3 seconds afer hey found i Ras ha failed o find he plaform wihin he alloed period were placed ono i by he experimener and a ime of 12 seconds was assigned n each rial he laency o escape ono he hidden plaform he swimming pah lengh he mean swimming velociy he heading angle a one body lengh from sar poin and he percen ime spen in quadrans and annuluses were measured To perform furher analysis he number of urns during each rial was measured Turning was defined as when he ra changed swimming direcion more han 9 degrees wihin one body lengh including a he pool wall Swimming in circles a he same posiion was couned as one urn To normalize urning raio was calculaed as he pah lengh divided by he number of urns Hisopahology Afer all behavioral examinaions were compleed he ras were anesheized wih diehyl eher and fixed by perfusion wih 1% formaldehyde in 1 moul phosphae buffer and heir brains were removed Five coronal blocks of 2 mm hick were cu from 112 o 12 mm anerior o he ineraural line according o he brain alas of Paxinos and Wason (1982) and embedded in paraffin Then 4-fLm secions were cu coronally from each block and sained wih hemaoxylin and eosin The area of cerebral corex and caudae-puamen (CP) of each hemisphere was deermined for individual secions wih a digiizer (Nikon Tokyo Japan) and he respecive oal areas were calculaed as he sum of individual secions The degree of shrinkage of lef cerebral hemispheric regions was calculaed as a percenage relaive o righ hemispheric regions o negae for changes in size of infarced issue Saisical analysis The resuls were expressed as mean ± SD for all parameers To analyze parameric daa repeaed measures of analysis of variance (ANOVA) followed by Tukey's pos-hoc es was used When dealing wih nonparameric daa Kruskal-Wallis ype of ANOV A was used and comparisons were done by Mann-Whiney U es Regression analysis was used o invesigae correlaions RESULTS General behavior Body weigh No deahs occurred in he MeA occlusion (n = 28) sham operaion (n = 19) or inac groups (n = 11) hroughou he experimenal period The body weigh of he MeA-occluded ras was significanly decreased compared wih ha of sham-operaed and inac ras (group effec F2sS = 837 P < 1; ime effec F J P < 1; group * ime ineracion F2265 = 714 P < ; wo-facor ANOV A for re- J Cereb Blood Flow Meab Vol 19 No5 1999

3 SPATAL COGNTON AFTER CHRONC FOCAL SCHEMA 485 peaed measuremens) A 1 week afer operaion body weigh of MCA-occluded group was 2837 ± 26 g which was significanly decreased (P < 1) from ha of he sham-operaed (397 ± 149 g) and inac groups (32 ± 14 g) However here was no difference beween he MCA-occluded and sham-operaed groups a 4 8 and 1 weeks afer surgery (one-facor ANOVA followed by Tukey's es) Neurologic examinaion Middle cerebral arery occlusion significanly disurbed boh he posure (Fig la) and flexor response of he conralaeral hind limb (P < 1 Kruskal-Wallis es followed by Mann-Whiney U es; Fig lb) 1 week afer surgery Alhough he neurologic scores showed gradual recovery MCA-occluded ras had significanly higher neurologic scores han sham-operaed and inac ras even a 1 weeks afer surgery Sham-operaed ras showed no apparen abnormaliies during he observaion period Locomoor aciviy A 7 weeks afer surgery 9- minue sponaneous locomoor aciviy was no significanly differen beween he hree groups (group effec F255 = 22 P = 142; ime effec F8 44o = 6663 P < 1; group * ime ineracion Fl6 44 = 168 P < 5; wo-facor ANOV A for repeaed measuremens) Bu whereas locomoor aciviy of he hree groups was almos he same a he iniial 1-minue inerval loco- moor aciviy of MCA-occluded ras a he second o fourh 1-minue inervals ended o be higher han ha of inac ras hence he mild group * ime ineracion (Fig C) Passive avoidance ask Seven weeks afer surgery performance in he passive avoidance ask was evaluaed using he sep-hrough es (Fig D) The acquisiion laency of MCA-occluded sham-operaed and inac ras was 112 ± ± 112 and 215 ± 157 seconds respecively n he firs reenion rial a day afer acquisiion MCA-occluded ras had a shorer sephrough laency (158 ± 188 seconds) han shamoperaed (2731 ± 87 seconds) and inac ras (3 ± seconds) (P < 1; Kruskal-Wallis es followed by Mann-Whiney U es) When ras underwen he second reenion rial 17 days afer he acquisiion rial a significanly shorer laency was sill observed (P < 1; Kruskal-Wallis es followed by Mann-Whiney U es) There were no significan differences beween shamoperaed and inac ras Morris maze ask Search behavior Eigh weeks afer surgery spaial cogniive funcion was evaluaed using he Morris maze Typical swimming locus of inac sham-operaed and MCA-occluded ras are shown in Fig 2 is noeworhy FG 1 Neurologic and passive avoidance performance in inac sham-operaed and middle cerebral arery (MCA)- occluded ras The degree of abnormal posure (A) and hemiparesis (8) was graded from (normal) o 2 (severe defici) Locomoor aciviy was measured for 9 minues wih 1-minue inervals a 7 weeks afer MCA occlusion using aciviy box (e) Sep-hrough laencies of passive avoidance ask were measured 1 and 14 days afer acquisiion a 7 weeks afer MCA occlusion () Each poin represens he mean ± SO (n = 11 o 28) The neurologic scores significanly increased in he MCAoccluded group The sephrough laency of MCAoccluded ras significanly decreased Locomoor aciviy of MCA-occluded ras ended o increase during he second o fourh inervals (* P < 5 ** P < 1 versus shamoperaed group Kruskal Wallis es followed by Mann Whiney U es; # P < 5 ## P < 1 versus inac group Kruskal-Wallis es followed by Mann-Whiney U es) ;: 12 u 1/1 U 1 1 e- ** 8 - ;:J 5 2 (; 6 8 a a a a a 15 4 c E A ime (week) C -- inac sham -- MeA ' ::J E 5 baa a a a a a cos B o ime (Week) * u >- u c c il ::J 2 = D inac --- sham -- MeA ime (min) -- inac --- sham -- MeA o 1 17 ime afer acquisiion (day) J Cereb Blood Flow Meab Vol 19 No

4 486 F YONEMOR ET AL session 1 session 1 quadran 1 quadran 4 quadran 2 (goal quadran) quadran 3 inac sham-operaed MCA-occluded MCA-n MCA-r FG 2 Typical swimming locus of inac sham-operaed and MeA-occluded ras a firs and las session Open circle indicaes he edge of swimming pool 144 cm in diameer which was filled wih waer o a deph of 32 cm (op view) Hached small circle indicaes he ransparen goal plaform 1 cm in diameer which was placed a a fixed posiion in he cener of one of he four quadrans (quadran 2) and he cener of one of he hree annuluses (annulus 8) Ras of all groups swam well and showed search behavior a firs session (op panel) Middle cerebral arery-occluded ras ook a longer roue han inac and sham-operaed ras a las session (boom panel) Middle cerebral arery-occluded ras showed wo ypical search paerns: one was almos he same as ha of shamoperaed and inac ras (MeAn) and he oher was round shaped and had less urning behavior (MeA-r) ha MCA-occluded ras showed wo ypical search paerns; one almos he same as ha of sham-operaed and inac ras wih several clear urns across he pool (MCA-n) and he oher quie differen from shamoperaed and inac ras wih a round-shaped locus and fewer urns (MCA-r) Cogniive performance The mean escape laency swimming pah lengh and swimming velociy ono he hidden plaform heading angle error a one body lengh from sar poin percen ime spen in goal quadran (quadran 2) and ouermos annulus and urning raio (pah lengh/number of urns) are shown in Fig 3 nac and sham-operaed ras performed his ask rapidly; 1 ± 81 and 26 ± 24 seconds respecively o reach he plaform in he las session n conras he mean ime in he las session for MCA-occluded ras was 626 ± 379 seconds wih 6 of 28 ras failing o find he plaform wihin 12 seconds The escape laency showed significan differences (group F2 55 = 1826 P < 1; session F9 495 = 1118 P < 1; group * session ineracion F = 247 P < 1; wo-facor ANOVA repeaed measuremens; Fig 3A) as did pah lengh (group F2 55 = 3341 P < 1; session F9 495 = 147 P < 1; ineracion F = 134 P = 16; Fig 3B) The percen ime spen in goal quadran (group F2 55 = 183 P < 1; session F9 495 = 452 P < 1; ineracion F = 192 P < 5; Fig 3C) and heading angle error (group F2 55 = 2236 P < 1; session F9 495 = 317 P < 1; ineracion F = 34 P < 1; Fig 3D) were also significanly affeced indicaing ha MCA occlusion affeced cogniive performance in he Morris maze Percen ime spen in he ouermos annulus (group F2 55 = 2378 P < 1; session F9 495 = 3391P <1; ineracion F = 427P <1; Fig 3E) as a parameer for circling around he pool and urning raio (group F2 55 = 123 P < 1; session 9495 = 65 P = 75; ineracion F = 84 P = 65; Fig 3F) as a parameer for swimming direcion change were also significanly affeced On he oher hand here was no significan difference wih respec o swimming velociy (group F2 55 = 14 P = 87; session F9 495 = 141 P = 18; ineracion F = 252 P < 1; Fig 3G) Furher analysis using Kruskal Wallis es followed by Mann-Whiney U es revealed ha hese changes in MCA-occluded ras were seen during he las four or five sessions whereas here was no significan difference beween inac ras and shamoperaed ras Analysis of differences in search paern To invesigae wheher he wo differen search paerns seen in MCA-occluded ras affeced cogniive performance we divided he MCA-occluded group ino wo subgroups according o mean urning raio (pah lengh/number of urns) wih a hreshold of 2 cm/urn because greaer han 2 cm/urn was rarely seen in sham-operaed or inac ras Resuls are shown in Fig 4 Turning raio of 12 MCA-occluded ras was more han 2 cm/urn (MCA-r) whereas 16 were less han 2 cm/urn (MCAn) By definiion he urning raio he group dividing parameer of MCA-r group bu no ha of MCA-n group J Cereb Blood Flow Meab Vol 19 No

5 SPATAL COGNTON AFTER CHRONC FOCAL SCHEMA f FG 3 Effecs of focal cerebral ischemia on acquisiion of he Morris maze ask Each animal was esed one rial per day for 1 consecuive days and escape laency (A) pah lengh (8) percen ime spen in goal quadran (C) heading angle error () percen ime spen in he ouermos annulus (E) urning raio (F) and swimming velociy (G) were measured Each poin represens he mean ± SD (n = 11 o 28) Two-facor analysis of variance (ANOVA) showed significan group differences in escape laency pah lengh percen ime spen in goal quadran heading angle error percen ime spen in he ouermos annulus and urning raio bu no swimming velociy ( p < 5 p < 1; wo-way ANOVA repeaed measuremen followed by Tukey's es) Middle cerebral arery occlusion affeced hese parameers during las four or five sessions (* P < 5 ** P < 1; Kruskal-Wallis es followed by Mann-Whiney U es) A i j 3 2 = 1 8 B C '" c f o session 8sslon session _'-----''--_'---_''-''-' o 8 1 session E 8 7 E i 6 _ B soo '" E E 4 H3 g> j 2 c a 11 F f G inac sham MeA session 4 1 session 4 1 session was differen from he sham-operaed and inac groups (group F3 54 = 4886 P < 1; session F9 486 = 228 P < 5; ineracion F = 241 P < 1; Fig 4A) On he oher hand escape laency (group F3 54 = 1318 P < 1; session F9 486 = 888 P < 1; ineracion F = 185 P < 1; Fig 4B) percen ime spen in goal quadran (group F3 54 = 1336 P < 1; session F9 486 = 29 P < 1; ineracion F = 136 P = 11; Fig 4C) percen ime spen in ouermos annulus (group F3 54 = 1557 P < 1; session F9 486 = 2679 P < 1; ineracion F = 31 P < 1; Fig 4D) and heading angle error (group F3 54 = 1551 P < 1; session F9 486 = 254 P < 1; ineracion F = 293 P < 1; Fig 4E) of boh MCA-occluded groups were significanly differen from hose of he sham-operaed group wih no differences beween MCA-r and MCA-n groups (wo-facor ANOV A repeaed measuremen followed by Tukey's es) These resuls indicae ha regardless of wheher MCAoccluded ras changed search paern or no cogniive performance of MCA-occluded ras was impaired Correlaion analysis Afer he behavioral invesigaion he degree of shrinkage of cerebral corex and CP of he ipsilaeral hemisphere was deermined as a percenage relaive o J Cereb Blood Flow Meab Vol 19 No

6 488 F YONEMOR ET AL 11 1 _1 2 E 9 ::J 8 a " 8 ' Ej 7 OJ 6 :Ee 6 E ::J : 5 5 ## 4 4 :5 " g> 3 E i A session 'U 8 g " 6 4 i " 4 8 " '" ;; 2 = 2 " ill B ssssion E 1: i 1 8 i' 2 6 ::J 6 <T - ii '" ;:: E 4 E 2 ::J FG 4 Effec of differences of search paern on acquisiion of he Morris maze ask Middle cerebral areryoccluded ras were divided by urning raio ino wo subgroup MCA-n and MCA-r Turning rasession io (A) escape laency (B) percen ime spen in goal quadran (C) percen ime spen in he ouermos annulus () and heading angle error (E) are shown Each poin represens he mean ± SO (n = 11 o 19) Two-facor ANOVA showed significan group differences for all parameers ( p < 5 P < 1; woway ANOVA repeaed measuremen followed by Tukey's es) All parameers excep urning raio of wo MCAsession occluded subgroups were significanly differen from hose of sham-operaed group (* P < 5 ** P < 1) bu here were no differences beween inac sham he wo MCA-occluded sub- MCA-n groups (# P < 5 ## P < 1; Kruskal-Wallis es followed by Mann-Whiney U MCA-r es) C sslon corresponding righ hemispheric regions As he ypical example in Fig 5 shows he area of cerebral corex and CP was decreased in MCA-occluded ras Alhough here was significan shrinkage in MCA-occluded ras (735% ± 14%) compared wih sham-operaed (993% ± 34%) he ipsilaeral hippocampus of MCA-occluded ras was no damaged as demonsraed in Fig 6A including pyramidal cells of he CAl region (Fig 6B) There were no significan difference beween he shrinkage of MCA-n group (764% ± 116%) and ha of MCA-r group (696% ± 74%; Suden's es) A summary of correlaion analysis is shown in Table 1 was found ha he escape laency (r = 421 P < 5) swimming pah lengh (r = 48 P < 5) and percen ime spen in goal quadran (r = 514 P < 5) of las session modesly bu significanly correlaed wih shrinkage of he whole slice especially wih he slice a ineraural 92 mm (r = 498 P < 1 for laency; r = 521 P < 1 for pah lengh; r = 421 P < 5 for percen ime in goal quadran) We also found ha escape laency (r = 492 P < 1; Fig 7 A) and swimming pah lengh (r = 483 P < 1) significanly correlaed wih shrinkage of cerebral corex secion from ineraural 92 mm bu no wih ha of he CP (r = 225 P = 25 for laency Fig 7D; r = 257 P = 19 for pah lengh) and ha he percen ime spen in goal quadran (r = 425 P < 5) significanly correlaed wih shrinkage of cerebral corex secion from ineraural 112 mm bu no wih ha of CP (r = 66 P = 74) On he oher hand urning raio and percen ime spen in he ouermos annulus significanly correlaed wih shrinkage of CP (r = 451 P < 5; 92-mm slice for urning raio Fig 7E; r = 437 P < 5; 112-mm slice for percen ime spen in he ouermos annulus) bu no wih shrinkage of corex (r = 349 P = 7; 92-mm slice for urning raio Fig 7B; r = 269 P = 17; 112-mm slice for percen ime spen in he ouermos annulus) The swimming velociy and heading error did no correlae wih shrinkage of any brain region There was also a srong posiive correlaion beween J Cereb Blood Flow Meab Vol 19 No5 1999

7 SPATAL COGNTON AFTER CHRONC FOCAL SCHEMA 489 phases of focal cerebral ischemia afer MCA occlusion in ras (Robinson 1979; Tamura e a 1985; Yamamoo e a 1988; Person e a 1989) has also been repored ha permanen MCA occlusion disurbs posoperaive raining of Morris maze (Markgraf e a 1992) and preoperaive rained memory for he Morris maze (Y onemori e a 1996) and he 8-arm radial maze ask (Okada e a 1995b) Alhough i is imporan o idenify how ischemic damage in a specific brain region affecs behaviors relaed o learning and memory few sudies have focused on his relaionship Recenly Okada e a (1995a) repored ha long-erm spaial cogniive performance was disurbed afer MCA occlusion in ra wihou any evidence of neurobiologic damage in he hippocampus n his sudy we invesigaed impairmen of spaial cogniive performance of Morris maze as well as neurologic performance in ras wih chronic focal cerebral ischemia and using correlaion analysis esimaed how infarcion of brain region relaed o spaial cogniive funcion Changes in body weigh locomoor aciviy neurologic deficis and passive avoidance ask of he MCAoccluded ras observed in his sudy are in agreemen wih previous findings (Bederson e a 1986; Obana e a 1988; Yamamoo e a a 1989b; Person e a 1989; Yonemori e a 1996; Wahl e a 1992; Tamura e a 1993; Hirakawa e a 1994) We evalu- 5mm FG 5 Typical phoograph of coronal secion of infarced brain for MCA-occluded ra he oal neurologic score a day 5 and shrinkage of whole slice (r = 725 P < 1) cerebral corex (r = 555 P < 1) CP (r = 553 P < 1) and he remaining region (r = 647 P < 1) The sronges correlaion was for he secion a ineraural 92 mm A 8 weeks afer MCA occlusion alhough a correlaion remained (r = 379 P < 5; oal score for whole slice) posure score (r = 4 P < 5; whole slice) more srongly correlaed wih shrinkage han hemiparesis score (r = 152 P = 44; whole slice) n conras he sep-hrough laency in he passive avoidance ask did no correlae wih shrinkage of whole slice (r = 252 P = 2) corex (r = 68 P = 73) CP (r = 288 P = 14) or he remaining region (r = 346 P = 7) including he coronal secion a ineraural 92 mm (Fig 7C and F) No correlaions was observed among Morris maze escape laency urning raio passive avoidance laency and neurologic scores (Fig 8) DSCUSSON is well known ha funcional and pahologic changes are observed in boh he acue and chronic FG 6 Microscopic phoograph of ipsilaeral hippocampus region for MCA-occluded ra (same sample as Fig 5) Hippocampus (A) and pyramidal cell layer of CA 1 region (8) are inac J Cereb Blood Flow Meab Vol 19 No

8 49 F YONEMOR ET AL TABLE 1 Correlaion beween ipsilaeral shrinkage and behavioral oucomes Passive Morris maze (session 1) avoidance Neurologic score % ime % ime in he Turning raio Sep-hrough 5 days 8 weeks Escape in goal ouermos (pah lengh reenion (oal (oal Coronal laency quadran annulus number of urns) laency score) score) Brain region secion (mm) p p p p p p P Whole slice Toal of slices neraura :1: neraural :1: neraural :1: neraural :1: neraural :1: Cerebral corex Toal of slices :1: neraural :1: neraural 92 O neraural neraural neraural Caudae-puamen Toal of slices neraural neraural Remaining region Toal of slices neraural neraural neraural :j: neraura neraural * p < 1 P < 1 :j:p < 5 (regression analysis) :]: * * 436:1: 397:1: * 399:1: 374:1: * * \ * :1: :1: :: * * 472:1: :j: 414:j: 41O:j: * aed spaial cogniive performance of Morris maze a 8 weeks afer he operaion when he residual neurologic deficis were mild and sable and when MCA occlusion had less of an effec on body weigh and locomoor aciviy Swimming velociy during all sessions and escape laency and pah lengh of he firs four sessions did no differ beween he hree groups which indicaes ha he neurologic deficis did no influence his performance There was no difference beween he sham-operaed and inac ras wih respec o pah lengh or escape laency which furher indicaes ha loss of sigh on he lef side or damage caused by surgery did no affec performance This is also suppored by he fac ha heading angle error did no differ beween sham-operaed and inac groups n conras MCA-occluded ras ook significanly more ime and a longer roue o reach he plaform compared wih sham-operaed ras alhough all MCA-occluded ras exhibied search behavior and successfully escaped ono he hidden plaform a leas once during he 1 sessions Percen ime spen in he goal quadran of he MCA-occluded group was decreased compared wih ha of sham-operaed and inac groups which indicaes ha MCA occlusion affeced spaial cogniion in Morris maze Turning raio (pah lengh/number of urns) and percen ime spen in he ouermos annulus which indicaes changing of search paern of ras were influenced wih MCA-occluded ras swimming circles around he pool and no changing swimming direcion compared wih sham-operaed and inac ras These resuls quesioned wheher he wo differen search paerns seen in MCAoccluded ras affeced cogniive performance We hus divided he MCA-occluded group ino wo subgroups according o mean urning raio Turning raio was used as a dividing parameer because circling swimming of some MCA-occluded ras was no resriced o he pool wall and hus percen ime spen in he ouermos annulus was no a represenaive parameer for he changing of search paern of MCA-occluded ras When MCAoccluded ras were divided ino he wo subgroups (MCA-n and MCA-r) he escape laency swimming pah lengh percen ime spen in goal quadran and in he ouermos annulus and heading angle error of boh subgroups were impaired wih no differences beween he wo subgroups suggesing ha changes of search paern did no affec cogniion performance bu affeced search sraegies We found ha spaial cogniive performance (escape laency pah lengh and percen ime spen in goal quadran) in he Morris maze ask significanly correlaed wih shrinkage of corex bu no wih ha of CPo The relaionship was mos apparen in he coronal secion from ineraural 92 o 112 mm involving parieal corex This finding indicaes ha he corex a leas in par conribues o spaial cogniion in he Morris maze We also found ha urning raio and percen ime spen in he ouermos annulus parameers indicaing changes of search paern significanly correlaed wih shrinkage of J Cereb Blood Flow Meab Vol 19 No

9 SPATAL COGNTON AFTER CHRONC FOCAL SCHEMA 491 " 1 r=o492 F=829 1 r=225 F=1383 p<oqj p=o25 y= x 8 8 E fje 6 _ E 6 g'o; 4 4 'E 5 i 1 c - i o': ;: 2 2 _ E " " "ai escape laency (sec) escape laency (sec) A (Morris maze session 1) D (Morris maze session 1) MCA-n MCA-r FG 7 Relaionship beween shrinkage of brain regions and behavioral oucomes in ras subjeced o MCA occlusion (n = 28) Lef panels (A B C) indicae correlaion beween behavioral oucomes and shrinkage of corex and righ ones ( E F) wih shrinkage of caudae-puamen (CP) of coronary secion from ineraural 92 mm " 1 8 E 6 _ E " "ai i' 4 ::J ; ;: 2 " : & Ji r=349 1 r=451 F=3596 F=6623 p=o7 p<5 y= x 8 QE E 6 " ai D_ =e : " 'C c "'E rf:::; urning raio (cmllurn) urning raio (cmllurn) B (Morris maze session 1) E (Morris maze session 1) 1 r=38 1 r=15 F=37 F=598 p=85 p= " 11- o BE 6 6 _ E _ E " " &ai "ai 2'; :" i ; : " ;: ;g C sep-hrough laency (sec) F sep-hrough laency (sec) CP bu no corex This indicaes ha CP a leas in par conribues o search paerns in he Morris maze Cogniive performance and search paern did no correlae wih reenion laency of passive avoidance ask nor neurologic performance which suppors he view ha neiher disurbance of passive avoidance ask nor neurologic deficis affeced spaial cogniive performance and search paern Whishaw e al (1987) showed ha bilaeral lesion of CP produced boh impairmen of spaial cogniion and memory reenion of Morris maze in ras bu no prolonged impairmen and suggesed ha when necessary medial CP-lesioned ras like normal ras can use place sraegies for spaial navigaion bu if an alernaive perhaps simpler axon sraegy is available hey seemingly ignore place informaion and navigae using a simpler sraegy They also suggesed ha he medial CP neural sysem is involved in he selecion of alernaive sraegies in spaial navigaion asks Considering ha cogniive performance of MCA-occluded ras was impaired regardless of changing search paern i is suggesed ha deficis of spaial cogniive performance of MCA-occluded ra in Morris maze are mainly associaed wih damage o corex involving parieal corex wih less conribuion from CP and ha changes of search sraegy are mainly associaed wih CP damage Reenion laency of passive avoidance ask did no correlae wih shrinkage of corex or CPo We have previously repored ha preoperaive rained reenion of J Cereb Blood Flow Meab Vol 19 No

10 492 F YONEMOR ET AL MCA-n c Us -i al 2 A o neurologic score (8 weeks afer MCA-o) 2 3 "5 F=O9 p--d67 4 'E& 1-1 E r" l D MCA-r -«- sham (mean±sd) "43 F=O48 p=o neurologic score (8 weeks afer MCA-o) 12 1 l 8 - r- 6 E i i?9 p=o ; E 4-5'E Eo a 2 "319 F=2948 p=olo : FG 8 Relaionship beween performance of Morris maze and oher behavioral oucomes in ras wih MeA occlusion (n = 28) No correlaions were observed among Morris maze escape laency urning raio passive avoidance laency and neurologic scores B sep-hrough sency (sec) E sep-hrough laency (sec) 12 1 is' - 8 Ej 1i 6 i; 1E 4 r- jl 2 c "333 F=3233 p=o8 \4 O -L o escape sency (sec) (Morris maze session 1) F 3 2 c r 1 i "39 F=O4O 1 p=o84 OL neurological score (8 weeks afer MeA-a) Morris maze ask bu no he passive avoidance ask correlaes wih brain infarc volume in MCA-occluded ras (Yonemori e a 1996) We also repored ha acive avoidance reenion laency bu no passive avoidance laency correlaes wih corical infarc volume in MCAoccluded ras (Tamura e a 1993) Taken ogeher hese findings suppor he idea ha differen brain regions conribue differenly o cogniive performance search sraegies avoidance ask and neurologic performance n he proximal MCA occlusion model we used fronal sensorimoor audiory and occipial corex and CP were infarced bu he cingulae corex hypohalamus globus pallidus halamus hippocampus subhalamic nuclei cerebellum and pons were spared (Tamura e a 1981a 1981b) Sysemaic invesigaion using lesion echniques in ras has shown ha bilaeral lesion of parieal corex affecs Morris maze card displacemen and acive avoidance performances bilaeral lesion of occipio emporal corex affecs maze visual discriminaion and acive avoidance performances bilaeral lesion of cingulae corex affecs maze and vesibulokinesheic discriminaion performances and bilaeral lesion of fronal corex affecs card displacemen bu no maze performance (Thompson 1978) Kolb e al (1983) sugges ha small parieal corex lesions produce deficis in spaial J Cereb Blood Flow Meab Vol 19 No5 1999

11 SPATAL COGNTON AFTER CHRONC FOCAL SCHEMA 493 behavior when a ask requires ha a paricular roue be learned and ha small fronal lesions produce deficis when he spaial locaion of he Morris maze goal mus be learned has also been repored ha bilaeral lesions of he parieal lobe (Kesner e a 1987; DiMaia and Kesner 1988) produce spaial memory impairmen of he ask in ras and Kolb and Tees (199) furher suggesed ha spaial learning is paricularly affeced in ras wih emporal associaion corex lesion Enorhinal corex lesions (Schenk and Morris 1985) produce impairmen of boh acquisiion and reenion Togeher wih hese repors and he resuls of our correlaion analysis he impairmen in spaial cogniive performance noed in our sudy may be associaed wih damage o fronal parieal or occipial corex afer focal cerebral ischemia n conras o hese findings Kolb e al ( ) have suggesed ha severe impairmen in performance of he Morris maze by ras wih fronal lesions are of he same magniude as hose observed in ras wih hippocampal lesions bu ha he fronal corex is no essenial for posoperaive reenion of learning This appears o be differen from MCA-occluded ras firs because he medial porion of fronal corex (cingulae corex) is spared in MCA occlusion and second as we previously repored because preoperaive rained memory reenion of Morris maze is also impaired afer MCA occlusion (Yonemori e a 1996) The damage afer MCA occlusion in our sudy appeared sronges in he parieal area whereas he correlaion beween spaial cogniive deficis and corical shrinkage was mos apparen in he coronal secion from ineraural 92 mm which involves parieal bu no occipial corex (Zilles 1985) Togeher his suggess ha damage in parieal corex afer MCA occlusion is mos likely associaed wih he deficis in spaial cogniion and ha fronal corex is less imporan The hippocampus which is no primarily damaged in MCA-occluded ras is repored o play an imporan role in spaial memory (Morris e a 1982) However Okada e al (1995a) using hisologic and elecrophysiologic echniques observed ha MCA occlusion was capable of producing long-erm spaial cogniive deficis in ras wihou significan damage o he hippocampus We also hisologically showed in his sudy ha hippocampus including CAl region was no affeced by MCA occlusion As here is no evidence ha he sepohippocampal sysem receives secondary damage afer chronic focal cerebral ischemia i seems unlikely ha he hippocampus is responsible for he spaial cogniion deficis in MCAoccluded ras is also known ha afer infarcion in he erriory of he MCA in he chronic phase progressive shrinkage occurs in he ipsilaeral halamus and subsania nigra (Fujie e a 199; Tamura e a 199; izuka e a 199) indicaing ha hese areas may also conribue o spaial deficis Prolonged spaial cogniive disurbance may likely resul from damage o several neuronal nework sysems a he same ime raher han a specific brain region n summary we have demonsraed ha focal cerebral ischemia causes a prolonged spaial cogniive disurbance in ras ha is correlaed wih shrinkage of he ischemic corex especially he coronal secion involving parieal corex and ha a change of search sraegies occurs ha is correlaed wih shrinkage of he ischemic CP and is disinc from neurologic or passive avoidance deficis The resuls sugges ha he long-erm spaial cogniive defici of MCA-occluded ras is in par associaed wih damage o he corex involving parieal corex and ha change of search sraegies of he ras is mainly associaed wih damage o he CPo These findings suppor he idea ha differen brain regions conribue differenly o cogniive performance search sraegies avoidance ask and neurologic performance and may be useful for esimaing he origin of funcional disorder in he clinical siuaion Acknowledgmens: The auhors hank Mr Asuhiro Vemura and Ms Saomi Takeuchi for heir echnical assisance REFERENCES Bederson JB Pis LH Tsuji M Nishimura MC Davis RL Barkowski H (1986) Ra middle cerebral arery occlusion: evaluaion of he model and developmen of a neurologic examinaion Sroke 17: Caplan L Babikian V Helgason C Hier DB DeWi D Pael D Sein R (1985) Occlusive disease of he middle cerebral arery Neurology 35: Caplan LR Schmahmann JD Kase CS Feldman E Basquis G Greenberg JP Gorelick PB Helgason C Hier DB (199) Caudae infarcs Arch Neurol 47: DiMaia BD Kesner RP (1988) Spaial cogniive maps: differenial role of parieal corex and hippocampal formaion Behav Neurosci 12: Fujie W Kirino T Tomukai N wasawa T Tamura T (199) Progressive shrinkage of he halamus following middle cerebral arery occlusion in ras Sroke 21: Hirakawa M Tamura A Nagashima H Nakayama H Sano K (1994) Disurbance of reenion of memory afer focal cerebral ischemia in ras Sroke 25: izuka H Sakaani K Young W (199) Neural damage in he ra halamus afer corical infarcs Sroke 21: Jarvik ME Kopp A (1967) An improved one-rial passive avoidance learning siuaion Psychol Rep 21 : Kesner RP DiMaia BV Crucher KA (1987) Evidence for neocorical involvemen in reference memory Behav Neural Bioi 47:4-53 Kolb B Tees RC (199) The Cerebral Corex of he Ra Cambridge MT Press Kolb B Suherland RJ Whishaw Q (1983) A comparison of he conribuions of he fronal and parieal associaion corex o spaial localizaion in ras Behav Neurosci 97: Markgraf C Green EJ Hurwiz BE Morikawa E Dierich WD Mc Cabe PM Ginsberg MD Schneiderman N (1992) Sensorimoor and cogniive consequences of middle cerebral arery occlusion in ras Brain Res 575: Morris RGM (1981) Spaial localizaion dose no require he presence of local cues Learn Moiv 12: Morris RGM Garrud P Rawlins JNP O'Keefe J (1982) Place navigaion impaired in ras wih hippocampal lesions Naure 297: Obana WG Pis LH Nishimura MC (1988) Effec of opiae anago- J Cereb Blood Flow Meab Vol 19 No5 1999

12 494 F YONEMOR ET AL niss on middle cerebral arery occlusion infarc in he ra J Neurosurg 69:98-13 Okada M Nakanishi H Tamura A Urae A Mine K Yamamoo K Fujiwara M (1995a) Long-erm spaial cogniive impairmen afer middle cerebral arery occlusion in ras No involvemen of he hippocampus J Cereb Blood Flow Meab 15: Okada M Tamura A Urae A Nakagomi T Kirino T Mine K Fujiwara M (1995b) Long-erm spaial cogniive impairmen following middle cerebral arery occlusion in ras A behavioral sudy J Cereb Blood Flow Meab 15: Paxinos G Wason C (1982) The Ra Brain in Sereoaxic Coordinaes New York Academic Press Person L Hardemark H-G Bolander HG Hillered L Olsson Y (1989) Neurologic and neuropahologic oucome afer middle cerebral arery occlusion in ras Sroke 2: Robinson RG (1979) Differenial behavioral and biochemical effecs of righ and lef hemispheric cerebral infarcion in he ra Science 25:77-71 Schenk F Morris RGM (1985) Dissociaion beween componens of spaial memory in ras afer recovery from he effecs of rerohippocampal lesion Exp Brain Res 58:11-28 Smih SE Hodges H Sowinski P Man CoM Leach MJ Sinden JD Gray JA Meldrum BS (1997) Long-erm beneficial effecs of BW619C89 on neurological deficis cogniive defici and brain damage afer middle cerebral arery occlusion in he ra Neuroscience 77: Tamura A Graham Dr McCulloch J Teasdale GM (l981a) Focal cerebral ischemia in he ra 1 Descripion of echnique and early neuropahological consequences following middle cerebral arery occlusion J Cereb Blood Flow Meab 1:53-6 Tamura A Graham Dr McCulloch J Teasdale GM (198b) Focal cerebral ischemia in he ra 2 Regional cerebral blood flow deermined by e4c]iodoanipyrine auoradiography following middle cerebral arery occlusion J Cereb Blood Flow Meab 1: Tamura A Yamamoo M Shimizu M Kirino T Sano K (1985) Behavioral change afer focal cerebral ischemia in he ra J Cereb Blood Flow Meab 5:S379-S38 Tamura A Kirino T Sano K Takagi K Oka H (199) Arophy of he ipsilaeral subsania nigra following middle cerebral arery occlusion in he ra Brain Res 51: Tamura A Nagashima H Tsujia Y Nakayama H Kirino T Sano K (1993) Behavioral changes afer cerebral infarcion in ras J Cereb Blood Flow Meab 13(suppl 1):S53 Thompson R (1978) A Behavioral Alas of he Ra Brain New York Oxford Universiy Press Wahl F Allix M Plokine M Boulu RG (1992) Neurological and behavioral oucomes of focal cerebral ischemia in ras Sroke 23: Whishaw Q Mileman G Bunch ST Dunne SB (1987) mpairmen in he acquisiion reenion and selecion of spaial navigaion sraegies afer medial caudae-puamen lesions in ras Behav Brain Res 24: Yamamoo M Tamura A Kirino T Shimizu M Sano K (1988) Behavioral changes afer focal cerebral ischemia by lef middle cerebral arery occlusion in ras Brain Res 452: Yamamoo M Tamura A Kirino T Hirakawa M Shimizu M Sano K (1989a) Effecs of a new hyroropin-releasing hormone analogue adminisered in ras 1 week afer middle cerebral arery occlusion Sroke 2: Yamamoo M Tamura A Kirino T Shimizu M Sano K (l989b) Effecs of a new hyroropin-releasing hormone derivaive on behavioral changes afer focal cerebral ischemia in ras Sroke 2: Yonemori F Yamada H Yamaguchi T Uemura A and Tamura A (1996) Spaial memory disurbance afer focal cerebral ischemia in ras J Cereb Blood Flow Meab 16: Zilles K (1985) The Corex of he Ra A Sereoaxic Alas Berlin: Springer-Verlag J Cereb Blood Flow Meab Vol 19 No