NOT TO BE TAKEN FROM THIS ROOM y Digitized by the Internet Archive in 2018 with funding from University of Alberta Libraries https://archive.org/details/extramazevisualcOOwend WmA^SAZB VISUAL CUSS AS A FACTOR lU MASE LEARHIEC IH THE EAT. Uy E«A, Wendt Presented to the Department of Philosophy in partial fulfilment of the requirements for the degree of Master of Arts, April, 1948.^ IHTEODUCTIOI 1. •The part placed "by vision in the hehavionr of rodents in maze sitiiations has "been a popular subject of investigation. Studies have been conducted mainly, hox'/ever, with reference to intra^maze visual cues. For example, Vincent (1915) ran rats in a maze in which the true pathways were painted black and the blinds white and found that the facilitation in learning v/as insignificant. The general impression has been that rats use vision very little in maze learning and that after a maze has been learned the animals run through it on the basis of kinaesthetic cues chiefly and are practically oblivious to visual stimulation. However it has been reported by Hebb (1938) in a more recent publication that visuaJ room cues determine an orientation v/hich in turn gives differential value to the visually perceived parts of the testing apparatus. It would seem therefore that extra-maze visual cues can be an important factor in maze learning. The problem of the relative importance of the various sensory cues available to the rat in maze learning has been thoroughly investigated. Various investigators have attempted to shov/ that some specific sensory information is the most important as an aid to the rat in learning to successfully negotiate a maze. The general techniques for investigating the role of sensory processes in maze performance can be classified in five main groups as follows: (l) Extirpation of sensory structures. It is possible to interrupt partic-alar avenues of stimulation ty removing the peripheral sense . •_ " 'i ''!' , . „ ^ ■ 'v''.'"'l:V; ,.pw>nr;.^ ■'“II'C''>;"’ suV;.)' ■i ^K ’.-! /> r.i •■,‘ f'-|f|!l;j ''. .. - - . •' r . ' •. -. ... _ 1. ^..1. (< -I- i-.'jv .■■4'' fi •' "ft. ^ll3^ d'l .©■d'X.-'r’x'; ■in':-”'?! al 'u:' ' idf, ^ . .'vSfeOT ■m •J' .'.' jv V'V y ;.t|ir-c-o, ■'<:.' xJ' ', tmxorti:.! '^:k ■* 'i .'.'ton ■ oil ,1" f. .; n lO I'.’O Ol!« V’-' ' ;. ^ '■ '...[ ' n.':, ' 1^' ill t , : :‘ fa.5i;'r?> i". ' '■ <• -i - : ■t.-Mo'tV'-.'' 0 :■* -.ij- oiif-i'- ■ . ^ ■'.V^tV. i ’i !1 .. .! v!.. '■ '•■ ' * ' ’’ -V ^ f <£ ‘ . .ij.U.iii- 2 organs, "by transecting the afferent paths of the cervical cord or hy extirpating the sensory projection areas of the cerehrnni.. Experimenters have investigated two types of problems by means of the extirpation technique. By operating on the animal prior to maze training, they have determined the role of sensory processes in the learning process. By opera,ting after mastery of the maze, they have determined the role of sensory processes in retention and in final control of the habit. (2) Elimination of stimuli. Some investigators, instead of removing sensory structures, have removed the sensory stimuli dii’ectly. One may compare the performance of animals trained in darkness with that of those trained in ordinary iiramination. Or one may deter¬ mine the effect of darkness upon retention of a habit learned in the light. Similarly one may remove customary auditory or olfactory stimulation. This method has the advantage that it does not interfere with neural integration at the same time that it removes the sensory stimulation. (5) Introduction of stimuli. Investigators have placed specific sensory cues in the true pathways of the maze and have compared the performance of snimals trained with such cues with the performance of animals in the absence of such cues. A significant difference in favour of the group trained ?/ith the specific sensory cues, providing the groups were comparable in other respects, indicate^the use of such sensory cues in maze learning, Eemoval of the cu.es after the pro Diem ha,d been mastered would indicate to what extent they con- ua • r. j . :u -■ ■ji. i - • :t . r- f! •-: o . .. : .; xiLs ■. . i. V.i. .1. . • 3. tributed to final control of the hahit, (4) Eearrangement of stimuli. "The role of sensory processes in mase performance may he determined hy rotating the maze daring or after training, Eotation of the maze changes the relation 'betv/een the environraent within the maze and the environment outside of it. (5) ‘The temporal maze technique. With this method one determines whether the animal is sJble to learn a pattern of response, for example rrll, without sensory cues of a differential nature. Sensory cues are rendered ineffective ‘because^mcist make a repetitive response in the same environment. 'The results obtained in studies of exteroceptive control indicate that the learning of the maze path?/ay is obviously dependent upon exteroceptive stimulation. There is no evidence \are at present which indicates the character of the processes which inevitably present during learning and final performance of the maze habit. Lashley (1929) made use of four mazes of differing complexity in order to test the influence of the extent of brain injury and retention. In the experimental animals there was aii average extent of injury of approximately thirty-one per cent of the cortex, differing in locus in different animals. An analysis of the data in terms of the locus of cerebral injury shov/ed, in general, that the amount of deterioration of maze habits depended, not on the locus of injury, but upon the amount of tissue destroyed. The hypothesis v/hich Lashley advances to explain his experimental results is ths^t W ^vr-*. IW,. !<■. liri ■ ■■ •■ frx ' 'c'i ; J ■ ; V. . ■ e '.' ’’ >k&' ' ‘i.0- ■ . ^ ' s* . '; 'f «’t'C ■ :.» , ■ . ^ 'I ' ' . " ■ “ C!i . W J ■■> v' 0 ‘ '^’4T ■ •" '■'•7 Oiixr I, ' 0..’;' - ’f V‘ ,1. .V' -i •> '.'a-..',j,, vv' ■■ . tvia^s 9. •■„: - . '‘. ’.i/f'w V. Is. I, t’ V* ' •'R ‘' ■ ■>v ' . l: :■ ^ .•* *ic,‘ £^(i, j^>c» ’ -u ‘t.>''<’ - ;%\X y ■C'/'l'- J. i :-'i:.At '-41 rt|if> jiSr ‘’,f J-'rv ‘If >:iL'- ■'•c y*4 «■ .totiiTwS ' ,>v;.; (.Jill-;. a^"- Ulli ■,i , , ■# ' ^>./:. Jit : *K>A '■I'X'' ,'' ' '-v ' "'S' ■li ‘ ■ . «,/:vjirA.jjriiM k ; ' I ^'' \' 4 the projection areas of the cortex have, in addition to their specific sensory or motor ftinctions, a non specific (perhaps f aci limitative ) function in which they are equi potential. An attempt has been made in this stiidy to implement a technique which may prove useful in the investigation of sensory control of the maze hahit. The method is "based on the hypothesis that the rat will make use of the most obvious cues most readily as an aid to learning a problem. For exaxflple if visual cues are the most obvious of those available to the rat the assumption is that the rat*s behaviour will be mainly determined by them. The comparison of the disturbances in performances resulting from the variation of the cues emphasized in a particular sample should provide a valid basis for determining the relative importance of the sensory process in maze learning. It v/as decided that a control group of animals in which the cortical visual areas had been extirpated would perhaps provide an adequate check on the performance of normal animals. Secause of the evidence in support of an equipotential function of cerebral cortical tissue a further control group of rats ?/ith lesions ( comparable in size to those of the visually operated animals ) involving an area of the cortex considered not to have a specific sensory function. 12 , ,^.i ; too.,.. -..' U%^4^;^-.: 3<*'/7.ri*I;v ■ f -^t .i^^n\f^>.. "■.'?f^ ,• .. JHy'(ii'^jp'2)y^,' Ct!./C'£T ''^„' !.0;^U^?•£J:. .',;?!* A i ■ - ' " ■■ ^ ^--v 'v rp- ■ ; nfW^i;;,. • ■..;.'l3..„ ri;:;. /folKv/' rii . "1^;/ ^^C'X^iri •eii'I;^' .ctl- oi-’Hw '■■; u- m' •^■' ,S‘"' >■ ^.0;;..'^u ''r/ ■ ’.ci:! ni. , ■ u.-c-A ■•■■-f '. ■•'••■ti ‘’ii^ "i-e A|'iarney : y; ."'C >r--. ' v'--0' .-:-.-.Tr -f '''to’ Xii-.':7 ;t s '’ ’'vi,j ! ■. ■ '' '• ' ' " ^ ‘ Ji S '-“7.': ■" i ■ .. ■' . ■ .. r . . '/■. '•“1 >0 ■r'M€' -4- 0# X'--'. C-'‘ v.:-o2V^C: trXj .M r , - ,..4 -iX.;' CroX^^l^tf 0 ^ {i|\ ^ . ''I?-:; >0 ac/.J-. i'.: ■■ •■.. 7v.cT V,;./ j ; . '-.' -■ ^ • |J -'*''' '“■■ ■ ■ ' . ■ - ;^;;..'.V’' , r ;'V?, . •• " ' ' -VoT^^iL U.l .■'7\VW^V -■ - ._ ‘:ir'';liki . ' '.. "'• .. . . - : xii.'i- - ;tt; 7 0 .•‘^T:^--.u-,*v,7Xvt7 .7. 4' /.v 4E^-f ■ ■ ■ *^ • r ' ' ''^' '/ r Ij?.t3i -:' '■■•44 .aXl" ' :•■ 7 ■ -^ . V i C4 .: . v; o ': o ^ 'to c» ■> ; 14 To’ -.o'^ t ;•; Xv;7.i, J:. 7;' ’-■ . ■ ■■*#1 { i - • -/it 5 APPAPvATUS Mii MTSEIALS A maze (see photograph) was designed which v/ould he adaptable to limited facilities and yet v/hich'*/ould present a difficult learning problem. The standard T maze would be most suitable for the invest¬ igation to be made but such a maze would be too large for the space a vailable. An adaptation of a maze designed by Walton (page 586, Ma,ier and Schneirla) was therefore built. The maze has twelve T choice points and a corresponding nmber of blinds. The alleys are four inches wide and each unit is fifteen inches in length. The interior of the maze x¥as painted with a flat black paint so that the various units of the maze present a uniform appearance. The entire maze was covered with wire netting. The arrangement of the blinds was made on the basis of a random selection which resulted in the following order of choices - rrlrllrlrllr. The maze used has the following features which contribute to its reliability ‘and objectivity. (Munn-page 217)(1.) The cul-de-sacs are of eq.ual length. (2.) The animal is presented with two similar paths at the choice points. (5.) The maze path;¥ay is of sufficient complexity to be difficult for the animal to solve. (4.) boors to prevent retracing. (5.) The performance of the animal is objectively scored. An intense extra - maze visual cue was provided by placing an unshaded 200 watt bulb and a 450 watt daylight lamp in the positions indicated on the accompanying diagrama. Light was alao provided hy '■ '■::M ' ■ " " '■ ’ ' , ,-, ■ . ■ fi .■ . . ■ ■ ^’- ■■ ■i '..^:i to; cr •ji;.T;i l-ew ^?Xjiaw' 05^*iS ^ OiiSAir O': . ■’..■■ 'itiiiV ..,:x.i:. ■:.x:':::n, %ru:^xeq0^&d''p b:k'’SXi:vi vy>ifSi.:i^y y r M" ' ' ■Vibiybb, /'■%, ■ .y. : ; ^ '■■ adi .' &:. .:;. ..v.4o:ii: m-J';-'. :' tis^ £i*4» fttti’ i;..rft*'J «»? •’ ■ ’ ' ' . .' •. ’- ' ‘ ■ \l- .■ \ ■ ■■' ■• • ■ -:■ ' , .;■’ ' •■ O' ,,o;vr,: O’" ;;T'^- C.. ::.vy';; :y,,ivxoXIOl' ^ ;'„ C-C ~:.'''v4 IQ a/i '.v^if^ f): # •^TOvu ; j’ i'.;„nl/j^" k^t.1: m4 P.40 4iM A -4 po .C^urittC.TO'^’^'-V' TiX'P: 4-y4\\y^ ■.,^ro,Y ?:if.v.>g^ra' l•f;’•Ov.;, „A.W #»■<- .:). .1 (' ■ .ytymNm- m I I'-'-i’ ' ivc '4 *• ai ; “•• i,5J ' •, iiji ,--<, j,:i? -’:> o overhead fluorescent hulhs and windows* Additional apparatus included a straight runway and a Lashley type jumping stand. The straight runv/ay’s construction duplicated that of the maze. The main features included were two retracing doors, manually operated as in the maze, and a food "box, (See fig.l. ) The runway v/as used as a means of preliminary training which would serve to familiarize the rats with some elements of the maze situation in order to expedite the initial training in the maze. Thus the animals were accustomed to the retracing doors, feeding in a food "box and the presence of the experimenter when first introduced into the maze. Stui ^ i Food box f 1 FUn of Sir^i^ht /?upway: - ffetrdciny doots The jumping stand v/as used to determine the ability of the experimental animals to make a pattern visual discrimination and thus provide a check on the extent to which visual cues might he M i '^U'% ^ ^D«;/v'r <|»|ujYO 4/ .1 U'nrr J' ■'?\ ':m&^ ’ - • ‘-A V 1 1 III II Ml Mmm’J ',■ • [.idJ'OCT ■;• ’ '»: C'-vr f:ST'7'V 1 V’ Yil|i ■ . v'c‘: -■ ir*- , '35ii? > - t't'J 'f'i^*2Ur. ;.i ■•«:* ■'■* '-0 ir.e!usC'£i ^ : fi i>c-a-<*- ©*■, .■ ■ ^ ■ ’ •'>:j ?;;■ . . ■ %J;-1.1 ' .i^ vtw' <>v . ■' ' , . ' ■ ' V as ■ • ■ i .v.l • ;;'.i.-I;;',t:‘' of yg ' ■ . , , iSa ■ * K ''’-• .: ■• /^ ■' ■ ’ " ;■>-''■,■■?'>'■ ' • ^'Fl 'r.;*j4';' •to:r'.v^5fii;;v.?q%t^ f iidu ^(^<3 ■' ’'''.’;i'?MV..'VWit'.t ^ vdFSs: «■ .A.,;i _ A' .r :: ' • vY’T ? .•A h ' ! »( . a\ 1 <.ACv^; Grvvi 3 f.'M ,5^ V-K it J - ~ ...»k ..w , :v:r- - I,-'" . -^r ■•■ ■ :fMlA./-’''i' V 7, operative, SURGICAL PBOCEDUES AliD In order to provide control groups animals were operated and tissue of the cerehral cortex extirpated Ly thermo-camtery. Of the animals operated eleven completed all training tests. Of this nxttnber seven Were animals vdth frontal lesions and four had lesions in the visual cortex. Operations were perfomed with asseptic precaution under deep ether anaesthesia. ‘The areas to he extirpated were located hy reference to sutures in the cranium. The sJrull was trephined on both sides of the 0 mid-line and the their^cautery inserted and swept in an arc ensuring an adequate coverage of the area to he extirpated. The size of the lesions was kept as nearly constant as possible. Histological examination of the brains using the technique ieveloped by Lashley was considered but rejected when it v/as found bhat there was insufficient time to complete it. ”‘'‘ W‘"S' t »'C'.:'' ■' ' ■ )!!■>., ■ ' ;A 0* •b'T; . •- 'V'b' . '•'- ■'. .to; V-' 7^':'.i: : ' V# m. hs«i!i!rf»-s? afi:Oi M? :--r:Ul£?«& "f'#'‘;'i i fil. j..a i; i 'b-r, c‘-' r:-:- ;: '■r\IX. a; .-.ri ,-r'h 8 TEAINIEa AiCD TEST PEOCEDUBES As preliminary training the rats were rim in the straight runxvay. The rats were fed daily only after completing the runs in the runv/ay and strong motivation to react positively in the maze JO situation was thus established. An arbitrary member' of runs was fixed as sufficient pre-training by this means. m _ \of\ of the w. M/\ZE i _ E. L£J INITIAU TRArtvlUStG- Ft jure. X El L'/yATs S- stiihtin^ point in Alaze F^food hox E 'experimenter W, W3 VJindoW6 The animals were then run in the maze with the lights in position A and the maze oriented as in fig. 2. Window W1 was covered throughout the course of the experiment. Windows W2 ¥/3 v/ere left uncovered during the learning trials. The rats were run one trial on each of two days, two trials on the tv/o succeeding days, three trials on the following three days and five trials each day thenceforth. The criterion of learning adopted v/as ten consecutive errorless trials. The use of a relatively high criterion was decided upon in J ; y1 i ' V. h:\ s '" ^ JL ' ''. t'^C:Xi::\Lm .l^^'e.. 1^**? :i. ;....' c:C' .:'■ ^-.r, , -y • ;:ov:;tv' -hn^^' Ism ■ ■i, ^ *;. ' ' ■ ■■ ' ..■ '• , _ , ■ f' ■ .,■■- ^ ' '• ‘ ■" -'i., ! 3T(\,vsf ■I ' 1 ■ ,. f • L;^J ■ : ri? ' o- ■ 'i r. ‘ '. o. .;; ■' -■ .,.P’ ■?» Tfci ( ' . ' ’‘yi'f ' / : 'x ■■■■ ) , "'. •■ . .■. 5!^ 4,1 % ~ ^ . ■ ip . ^ , :' S;' V; ^ ^ W'- ;^V'J\ - \ vV . • ..X riiTi rt ,mMlv ■ ■ ’ • , ■ ' '■ ‘ ••• 'ri O' '7 ’*r.v iXO ..1-- -'.'tj r . ‘ : :^ . ' :> J- • .•‘I iin;' :'.i;; ' • ;• . , ^ ,i7i>c>OQr‘. .' ; ■';' ■..J^^l■lc' ./'■■ '■ 9 order to make more significant an^ deviations which might occxix during the test. The tests devised were three and each involved rearrangement of the extra-maze visual cues* {bJ Lit}hf6 5- sTdirtin^ point f - fdof/ bc»/ W, Wi Wd VJindo\n/6 E’ z k ptt/m cnUf'. In the first test the windows W2,V/3 were hlacked out with heavy cloth hlinds and the lights v/ere moved to position B. (See fig* s) Othenvise conditions were left constant* F i ^ 5' Point f- pood h o% Wi Wj ^5 " L*- t% pzrinizntct v:f!- u^'y'.'A-S ■'/>. _■, ■>• a >1 ; ;■ ^ >V V : - ■ ' ■ . '\-f\ /■ ■.■■,.:^ . . .Of' _\V pf.,'- , ,v ':f ;frv.'-; v^:,' , P-al V. ■ ^ ^ ■ iH^'> .'■‘V rm WKM vv • : A 5 i A;:.. . . V^;. * V‘/ 10 In the second test the mase was rotated to the position shovm in fig. 4. “fhe windov/s were darkened as in Test 1 and the lights were in the same position, relative to the maze as in the first test. In the third test, which was used as a control to check on the effect of rotating the maze the lights were in the same position in relation to the maze as during the learning trials hut otherwise conditions v/ere as in Test 2. The animals v^ere given retraining under the original conditions between tests and brought back to the criterion of learning in each case. The rats were run twenty trials on each of the tests. The rats were then tested on the jumping stand. They were first required to make a discrimination between a white and a black card and subsequently were tested on discriminating between patterns formed by vertical and horizontal lines. ;u, ' art q;?’ ;>v ‘ ">' r -. i{jr< •o.t X^>’^vl■,^^• T' spdsM 4l'y \ '.'V ■. #> « ■'% '. t '" - 'f!j:'^'“'' bv'iv ... ■.;--; i.:l-ir-^ :d ^0 f '" ^ ■ I ,r,!.,otf Xm0.t'ii ■ : ■ ■ >yrg!^TOSM^ ,-.. .-: ‘‘^ ^' V '^^•r ■f c.; ; X HwT iil 5%iT.^J .y r - K-' ' ■' H 0 ' & asi ^ ;■■■- t,. ''t' Irt ioiiis , II.O- ,0?!' -V' " }'■'’" ’ "' ft- [:T XJZ D I 'd'i,dy> ;‘;.rr -•'*v'r^rt;< 11 BESULTS ITine normal rats, six rats vdth frontal lesions, and fowc rats v/itli lesions in the cortical Visual area completed all training and test runs. Five animals v/ith occipital lesions and three with frontal lesions died during the training. One animal with a frontal lesion Had not learned the maze after 435 trials and one with a visual area lesion had not learned after 590 trials. The mean number of trials for the normal animals to achieve the criterion of learning ?/as 1E6 trials; for the frontall^^ operated animals 247 trials and for the visually operated ^20 trials. The performance of the three groups on the three test situations is summarised in the following table. TEST 1 (20 trials) TEST 2 (20 trials) no, of Errors S.L ItE AX'! no. of Errors S.B. HOEhAL 15.67 5,4 14.44 8.15 EEOETAL 28.33 10.1 30.5 7.01 VISUAL 0.5 0.86 0.5 0.86 TEST 3 (20 trials) ivdilAE no. of Errors S.L. IvOEL^AL 0.53 0.66 EROKTAL 1.53 1.38 VISUAL 0 0 The results obtained in the third test situation indicate that potation of the maze does not significantly affect performance if the dominant extra-maze cues are rotated with the maze. The close correspondence of results on Testl and Test 2 indicate a similar ■ , ,. ' ivV ■ ' , ‘ !jy ■■ . . ■. ' ¥ :■ ,jsis^^i'oxUi:U J' " ' ’ " ' ' ■' ■ t'' ^ ; 0 . ' :■ '.. ' ■ ,^ 1 •■ '■ ■ -’7^1 : ■: ■■■ '■ ,f. ..i,':.x-, ■■ . hxlxa''^: XJ.'J' :. . : : '.■' ' xJ ■ ■■o.rx , -'■o ■;:■ 0''y: 'ifeii : o.^. ^^^. • « •' .. ;. OW'ffl'jy'k'O,, ;. ,o , 0>C ■ ■^.:'' ,,^Xi' ,iv Vy: si'fo'oi..' 1, ' . .yt ' 'o"*: '■ sx,y;{^a.L'X:,f?i;^aS;4 ,; "y: ;; ,5, *': ', , i;v , 12 conclusion. In this study the disturhance of the relationship between the internal environment of the maze and the external environment was found to cause a disturbance in performance but when the maze was rotated and only the dominant visual cues were maintained in the same relationship no disturbance was elicited. The animals which had lesions in the visual cortex were not affected by changes in the extra-maze visual environment. Eats with portions of the frontal area of the cerebral cortex extirpated exhibited a much greater disturbance in behaviour than normal animals when extra-maze visual cues v/ere altered. The tests of the rats on the j~amping stand v/ere not concluded because of a lack of time but there was an indication that the visually operated animals were unable to make a pattern discrimination in which the normal rats and those with lesions of the frontal area of the cortex were successful. Vi ,: \ Y£i: ■ - i.‘ I r. '^I'i^ '‘’''iV Vi . H iv£ft 1:^ ■' ■ ■'■ . - {jJtV-tf W’ 'fW 1 Vf « .“ifilia r* iVc<; X,r.;.t^iXv A' ’ * '- ■i-Xt xt' ■, • i Y v c wKIKmi^ V fe il.' ’ Iri'K ' ,'■■ ■'. ■ o ■T^'K i^S^'’" ■jffV- , .';4 ' vn ' ■■• ^ 'T ^ ,if '■^ 01^'^ 8j/' r|, 'iSt ,^mp'isftm :ir mm^ ^“SfW3‘ t^rS wUi? 'tvs . '^m '. wv. i i-' .^•;-: : t :': -1 dX4Y ' ■ . . ;.v :: fi4s^* f5!^4 ?f '. •' ■ ■ ' fc iM 'H.. '^>v '■ " ' V . ■V,:-." /i.VV.fH" ': :?>; v>'5^ ; Y ^ 13, DISCUSSION On the he-sis of the data obtained in this stMy there seems to be an indication that eztra-maze visual cues affect the maintenance of the maze habit and are probably operative in maze learning. The normal animals and those v/ith lesions involving frontal cortex were disturbed in performance, on a basis of error scores, when the extra-maze visual cue was altered. The fact that those rats with occipital lesions were not affected by the disturbance of the extra-maze cue provided indicates that these animals had Learned the maze by some means in which the extra-maze visua.1 cues were not a determining factor. All animals were brought back to the criterion of learning between tests under the original conditions. Since all animals in which disturbance in behaviour had been elicited during the test situations made a rapid readjustment during re-training it is suggested that the extra-maze visual cue was a determining factor in the formation of the maze habit. The results on the tests involving rotation of the maze indicate that disturbance of performance is due to an alteration of the relationship between the internal environment of the maze and extra-maze environment rather than the directional reorientation in itself. Careful studies involving rotation of a maze ha,ve been made by Cengerelli and Higginson. G-engerelli (1988) used a conventional maze with six blind alleys which was surrounded by a screen three feet high attached to the maze. An effort v/as made to eliminate all extra-maze stimulation. After the animals had 1 ■j . irsi .'ow>im ■; ; .1 \t '3'' V:i4:i;t' '^.v -bntti n-'-i . •- ky?.' Cf^dst ; •. -• af’i.^.ri:?. ^ '■ ' @ '"'" "'i' <’ ^’./ ijjtwX . '■ .: :: mM ■ . . ’‘ J :r. ‘'C€TZ<*' ST [,4*77 ■'^■^ (i bul o^uXp •'rf6^^U0h‘^f ^ fMz 3 (jfi;; i'l3&'UJ4!*«itf..* J'S'i-' af»w«!fliSri-ff®fi'!Tro'ai ai"';) ssate-^tfeis^ mMm9 B “■( J O '1 =4^4:1.'/ >4^ Jiipicit^ ai .®4f?' aX.wl'«4s ^MA 477:'%*- •jd'oiviiiOci txj; 4^dw uf n-^’. SK" liSW , , '' V;;.; ' ' '''' 0','i^ to iiviti.%u'i*-tv! ,(al to-wl '■■ --"--“iM , ■' * -^f.a !'. , XlXo-i:^5r^ 'rsj^r fist .'r,:;i.> ^-,"^>1 i Unll\ .M 4X1^ oi'Vi iywol . • - ' fw* # X 3 Ollttt I 0.-: ^ :r^y©t7'Wt.4XA ti f>r> 14 mastered the maze they v;ere required to r-uja it tv/ice with a 90 degree rotation and twice with a 180 degree rotation on successive days and disturbance in behaviour was elicited. Higginson (1930) found that in preliminary tests made under ordinary laboratory conditions where heterogeneous stimulation could influence the animals, rotation led to marked disturbances but when animals were trained in complete darkness rotation in darkness elicited no disturbance. He found further that animals trained in a covered, internally illuminated maze were not disturbed by rotation tests after the maze had been learned. Higginson states that he could find no experimental evidence which would substantiate the claim that the rat possesses a sense of direction by virtue of which it is disturbed when the maze, previously learned at one position, is rotated to nev; cardinal positions. The third test in the study being here considered involved reorienting the maze directionally in an environment in v/hich heterogeneous stimulation could influence the behaviour of 'the aiisitsd: animals* Since no disturbance in behaviour was elicited in the third test situation it was suggested that a constant relationship betY/een interior environment of the maze and exterior environment was maintained by keeping the provided intense source of visual stimulation in a constant position relative to the maze. Thus it would seem that a specific sensory cue can be a predominantjfacor in retention of the maze habit. V'’’ '^■'‘(:S9M^ i >ji tfl: £'"> o-r s:) :: i-i Vv. jfj vr^*/ .1 .'-‘ t’lj ', ">r^ ■ lo^r^'y ui ^ ot ,1 -I .^o or te ■ ■" ■■ ' ■ r^3j- ^ , . ■;,; ;■ ■ ' ■. ■■ ' ' ■ '._. '-'.Jr'-'r-.: '„■ t.iJJ •lO/-':oo »4' .MOvIS: V Jr -: ..1 &? •= , i i on i>^v%d2:Xo ' tsf fW.-':: sli. ^ ' 5 .-'.g!. m 'X.?%^wv^ '.u • , ‘Wi .r> g ^ Si ,^“£ . . •:• ^u'W ■ '•=’.‘' • '■ , is.' ■ myft ' • '■4/i .^ (,.' ■■ ■•' ' , . ■■;■'■- • i*' ■■■''■. ; if# ' P : ot :^i. o%a. ' /■■- & ? . . ■ -v ffZ i av. ao 1- :■ ;■ ,v •; , mr. vkt m- i: ^dt] .^lU 'y-< ■ : ■,'® ^ vO;. o,.-p|;p_ rtriOilni f4.:.-..u iXs-S. 3 BuJiiiHi- r*. ‘ . "" r.',l .iSUl V O-.iM •' .’iiS i 'r< ti'|irff r.;^Y 'i-iv. *,s?i',i»if s-ii,« '#;■ :ii "C r I v^Tt> to>i:''j:Jcj.i: n(^ %a lA’inAjijriiaf?: Jt j^-r =* •>>t^ 15 The close correspondence of resiilts in test situations 1 and 2, in v/hich the relationship of the extra-maze visTial stimulation to the maze was constant although the maze was rotated directionally in the second test, indicates that rotation in itself does not disturb the performance of rats in a maze previously learned. The neural mechanisms involved in learning are yet to be understood* Two facts which are applicable to the problem must be considered* First, there are sisbaxats numerous sub-systems in the totsJ nervous system each of v/hich are capable of elaborate integration* Secondly, any sensory pathv/ay, however simple and restricted, leads ultimately to every effector* In the solution of more complex learning problems a greater portion of the nervous system will contribute to the production of activity. With a greater part of the nervous system involved there is a greater possibility of flexibility in the participation of the various afferent paths. Thus the animal deprived of some sensory inform- 3, tion is still able to learn. However if the integration involved in learning a problem is influenced by a particular intense sensory cue there should be a reduction in the possibility of flexibility in the use of the various sensory processes. Animals that have lost the use of part of the nervous system as a result of extirpation would probably be at a greater disadvantage than normal animals if adaptations to an environment v/ere necessary for bhe maintenance of a learned habit* In the resiilts tabulated above the animals which had lesions . ■ y .- . ■ '.- , '.'■ '■'' -.' ' ■' ■?■ ' ' ■ r'o i.'‘....,;:v ■ .-.yavX''? 4 ni: «'' ■ i i v-*jJT/ b -y* *r. •yvr v.;; «;■■■; u^td' yri# 0;? ‘:Z i'' .''X no dv-^v'-i/ . . y ^ ■5'eJ. ‘/,_..:j 0:.' -'.r' "i a i. tjd'tj*': : } : :• .■•- ..iOX'-'o : f/1 b^ijvlo vill: sS?-; trui«.':;t>KI ■ ■ ■ ^ ' , W I:* i-!, -J. f.jtv.,:- tf%d, ' 61' !•’ 'C‘^-7.^ r-.. ’ . ;^va1djr:'r- b/r'i . ', ^ -{C r.j ■ . . ' ^ ’ ■.;■■•■ ;■ ' ; ^M . r .... :•.: . ^ey -‘te '^uVi> cJ- riF ^ xr' rrjid’t'o^ 'r->da«Ty ,v.V4:y: oi jj.nit to :) o i i iv; . '/.^&;v . . # ■' y' yrj Id rfott-r.^:oi&'m. y^U .i?t %o' O'..;. .- yrb^iil^fi via;?' m 'm /; A rtc:J.:.'iy i O^.d 'l£ -J'yfO'.jO . X&t-K ©1 cfo-iddsy''^' : ■ . ;: X ^ j2<. ?£. f.’ :T^:a-..CvXC a‘ -■'f' ,Ai . .. , . ;y<: A r-: '-. ; :-rfiX;r^iXrx«0itn. h bp-yy.:-. ^yt^m 'i ’■ ', _ ■ . ... /..f ^ .•v : ' X-'j-lJ -- • -i.v :?i34fev; av C:^ s>>-.v ; ‘ , , ''My dx:K|, 5''i30 .C '10 rlvcf.-. y y. .-■ .fo'CG ‘y ‘ j'.'^rf'f y n .. .A- * y 'c,c ,»llt.Xu».*X O.vil .'Ivi..'., cX,*:.:.. 16. involving a frontal area of the cortex were disturbed, tv;ice as much, on the basis of mean error scores, as normal animals in a situation which required an adaptation to a changed environment detemined by the rearrangement of an intense extra-maze visual cue. It is suggested that this result may be due to a comparative inability on the part of the frontally operated animals to adjust to an altered environment in v/hich the use of exteroceptive stimulation other than the changed source v/ould be necessary for retention of the maze habit. The apparent lack of flexibility in the use of va,rious sensory information of animals with frontal lesions could be due to a deduction in the functional quantity the nervous system available. The possibility of some special integ¬ rative function of some portion of the frontal cortex may other¬ wise be suggested on the basis of the results obtained. It is suggested that a more adequate study of the problem investigated should include the following features: (1) The use of a larger number of animals in order to ensure a more relia-ble sample, (2) Post-mortem histological examination and mapping of the 0 size and locus of lesions of operated animals. (3) The use of a self-recording, automatic maze, (4) variation of the order in which the test situations ai^e presented in order to control the possible effect of over-learning on the second and third tests. ■r:v; !:;.,> :^.> AKiif'si.i#];:, c# (7 X uf ■ ’. i» : .cxic .J ... / JM‘‘] *5^ f".'." . .'b . A vSC^t*! V C ic ./Vvfe^ :,: ■;.Trt,'C '.tO oci^r ■ ■ ■■ 'i^‘' ■ sv ...^' f'CJ’j'iV It: cvj '••■ v' '‘jfj.CV '-.-:T>;rcss - ;i|jSLrfs ( 0 /:vt c .'>4::;.: . c. -.:o:^r^>r^ ic ’lid r. - m^ QWh^Pis :| , '; Ck;j ■:., . ,V ' ' -.-' .- ~ 1: ■ i ..' VC - fife ' .> vt ; 'ib dicv ^v'i - ’ .■ • ■■ i" . . ••. '■■ 'J i.-v'to:-. 1 ' 5-;'ig e"j - , . I j'- .' ' :0^' ... ....-> ■■; ibUKjdi*? r' ' 1 ' '^ -. ' ■ '■' -vC 'H '"i:^ kH' . vj X:4i'^-:t' tx 'J> ■■;, . .. ■ ,.!t »' \f i ' A XKv'lt . 4JL ^.- '4^^ .1^1 Sli.- ': .: :i-/ .1 C ., rjsit^z ?Mv;- •. ..,.,C . V n a . . :■ .--5? sy ■ ’■' ■ r /.«*» vr . • ijiv" ■■4;^ (1) Oengerelli J.A. 1928 J. Comp. Psyciiol. 8, 577. (2) HeBB B.O. 1958 J. Comp. Psychol. 25, 553. (s) Higginson C.B. 1950 J. Comp. Psychol. 10, 555. (4) Lashley K.S* 1929 Brain Mechejaisms and Intelligence (5) Maier II.H.F. and Schneirla T.G, 1955 Principles of Animal Psychology. (6) Munn W.S. 1935 Animal Psychology. (7) Yincent S.B. 1915 J. Anim. Behav. 5, 1. 19 APPEilDIX TABLE 1. Total errors and total trials made in initial training, in test sitriations and retraining after tests. EKEOES TKIALS Eat Initial Test 1 Eetraining Initial Test 1 Eetraining Training after Test 1 Training after Test GEO UP i EOEIoAL 1 471 7 0 183 20 10 2 442 10 0 192 20 10 5 228 16 0 175 20 10 12 187 14 1 82 20 13 13 171 21 0 61 20 10 15 276 25 0 96 20 10 22 322 19 0 148 . 20 10 23 142 11 0 57 20 10 24 392 18 0 144 20 10 GEOIXP 2 EiESIOES IE lEOlITAL COE'rES 4 519 19 1 266 20 14 5 1233 19 2 348 20 12 6 860 46 2 285 20 11 7 570 31 1 177 20 19 17 579 27 0 230 20 10 18 540 30 1 176 20 19 mOUP 3 EUSIOIS II VISUAL COETBX 9 1246 0 0 280 20 10 11 860 2 1 268 20 13 19 485 0 0 166 20 10 21 538 0 0 170 20 10 20 TABLE 1 (cont’d) EtiB.OES THIALS Eat Test 2 Eetraining Test 5 Eetraining Test 2 Eetraining Test GliOUP 1 1 4 0 0 0 20 10 20 2 11 0 0 0 20 10 20 5 29 0 2 0 20 10 20 12 12 0 1 0 20 10 20 15 6 0 0 0 20 10 20 15 22 0 0 0 20 10 20 22 16 1 0 0 20 11 20 25 7 0 0 0 20 10 20 24 25 0 0 0 20 10 20 GEOuP E 4 20 1 5 0 20 11 20 5 52 0 0 0 20 10 20 6 52 0 2 0 20 10 20 7 55 2 0 0 20 11 20 17 24 0 0 0 20 10 20 18 42 5 5 0 20 12 20 GEOUP 3 9 0 0 0 0 20 10 20 11 2 0 0 0 20 10 20 19 0 0 0 0 20 10 20 21 0 0 0 0 20 10 20 Bet ID L 10 13 10 9^ SI ■■ t;',