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78 2 Am J C /in N u tr 1996 ;63 :78 2-6 . P r in te d in USA . 1996 A m e rican S ociety fo r C lin ic al N utrition

Lea rn ing d isab ilities and poo r m o tiva tion to ach ieve due top ro longed iod in e de fic ien cy13Banarasi D T iw ar i, M adan M G odbo le , N a ib ed ya C ha tto padhya y, A n ita M anda l, and Ambr ish M itha l

ABSTRACT Th e effec t o f p ro long ed iod ine de fic iency o nle arn ing and m o tiva tio n w as stud ied . O n e hundred m ale ch ild ren-m atched fo r ag e, soc ioeconom ic s tatus , an d fo rm al edu ca tion -w ere se lec ted from bo th severe ly io d ine-defic ien t (S ID ) and m ild lyio d ine-defic ien t (M ID ) v illag es . M ean urina ry iod ine excre tionw as sign ifican tly low er in the SID than in the M ID group (2 19 .84 57 .52 com pared w ith 449 .14 32 .3 1 nm o l/L , P < 0 .00 1). T heserum thy rox ine co ncen tratio n w as sign ific an tly low er (9 0 .3 6 6 .4 6 com pared w ith 123 .70 15 .42 nm ol/L , P < 0 .001 ) andserum thyro id -stim ula tin g h orm one (TSH ) w as s ign ifican tlyh igher in the S ID group than in the M ID group (6 .23 0 .34com pared w ith 4 .85 0 .28 m U lL , P < 0 .01 ). T h e ch ild ren w ereadm in is te red m aze , ve rba l, an d p ic to ria l lea rn ing tasks an d a test o fm otiv ation . T he resu lts show ed tha t S ID ch ild ren are s low learnerscom pared w ith M ID child ren . In bo th gro ups th e ra te o f learn ingover trials w as sup erio r in yo unger (ag ed 9-1 2 y) ch ild ren a l-though the in itia l p er fo rm ance of o lder (aged 12-1 5 y) ch ild renw as be tte r (P < 0 .01 ). SID ch ild ren scored sign if ican tly low er thanM ID child ren o n the ach ievem en t m otiva tion sca leP < 0 .01) .T he resu lts a re sug gestive of neural im pa irm en t as w ell as poo rsoc iop sy cho log ic stim u lation , resu lting in learn in g d isab ili ty andlow ered ach ievem ent m o tiv ation . U n less iod ine nu trition is im -prov ed in th e com m unity as w hole , these abn orm alitie s m aypreven t m illion s o f ch ild ren from the S ID areas from ach iev in gthe ir fu ll po ten tial even if lea rn ing opportun ities are m ade ava il-ab le to them . Am J C lin N utr l996 ;63 :782-6 .

KEY W ORD S Iod ine d e fic ien cy , learn in g d isab ility ,ach iev em en t m otiva tion

INTRODUCTION

C er ta in spec ific cog n itive an d in te llec tu al fun ction s, eg , ve r-ba l and percep tua l perfo rm ance , m em ory , an d m athem atica labstract ions, are particu la rly vu lnerab le to iod in e defic iency assu ggested by serious im pa irm en t o f these capac itie s in c re tin s(1 , 2) . A v ailab le in fo rm atio n d oes n ot ind ica te an y gro ss sp e-c ific d efects a t phy sio log ic o r fun ctiona l leve ls in severe lyiod ine-defic ien t (S ID ) popu lations o ther th an cre tin s; how ev er,it is genera lly reco gn ized tha t the spec trum of c lin ica l fea tu resex tend from m ild hypo thyro id ism to frank cre tin ism in affec tedpo pu la tion s. T he su bc lin ica l e ffec ts o f io d ine defic iency oncen tra l ne rv ous sys tem (CN S ) d ev elo pm ent and fun ction tha ta re m ore sub tle in na tu re m ay be d ifficu lt to de tec t b y co rn -m only u sed in telligence tests (3 ). T hus , a lte rna te m ethod s totest the e ffec ts o f io d ine defic iency in u tero on f lu id in telli-

gence represen ting th e bas ic neura l ap para tu s are necessa ry .M ore dynam ic tes ts to m easu re lea rn ing ab ility and the efc iency by w hich n ew info rm ation can be absorb ed an d pcessed have recen tly b een recom m ended fo r assessm en t o f te ffec t o f iod ine defic ien cy on lea rn ing po ten tia l o f ch ild renendem ic areas (4 ). G iven the n um bers o f ch ild ren a t riskiod ine deficiency w orldw ide , th ere is su rp rising ly little in fo rm ation on th is im portan t aspec t (5 ).

I t is now accep ted tha t s ligh t bu t p ro longed low eringc ircu la ting concen tra tio ns of thy rox ine (a lthough w ith inn orm al range fo r th e p opu la tion ) m ay prod uce s ta te o f ce re -b ra l hyp o thyro id ism in the c lin ica lly eu th yro id popu lationsS ID areas, w h ich m ay lead to slow m enta tion of th e w hosoc iety (6 ). A ssessing th e effec t o f iod in e d ef ic iency on so cio -cu ltu ra l stim uli p rov ided by s ib ling s, peers, pa ren ts, ne ighb ors ,an d the com m un ity as a w hole is im po rtan t to q uan tita tev ariab les like m o tiva tion to ach ieve . A s such , th e req u irem en tfo r m ethod s to test in te llig en ce th at re flec t the con tribu tionsoc iocu ltu ra l va riab les and capacitie s acqu ired th rough lea rn -ing and particu lar ly th rou gh exposure to ed uca tion a lso canno tbe ov er lo oked (4 ). B ecause m otiva tion to ach iev e an dab ility to learn (7 ) a re tw o im portan t aspec ts o f in te lligence ,inv estiga ted the effec t o f iod ine deficiency on th ese variab les .

SUB JECTS A N D METHOD SSubjects

The presen t s tudy w as carried o u t by using s im p le ran -dom ized grou p d es ign in w hich th e tw o gro ups w ere m atchedfo r ag e, soc ioeconom ic sta tus, and fo rm al edu cation (8 ). Wse lec ted 1 0 iod ine-defic ien t v illages from the P adruana reg io nin easte rn U tta r P radesh , Ind ia . T he p reva len ce of go ite r w> 60% and the cre tin ism rate w as 3 .4% , ind ica ting SID . F ouv illages o f the sam e reg ion w ith go ite r ra tes < 10% and w ithou t any cases o f c re tin ism w ere ch osen as the con tro ls. H ow

I F rom the D epartm en t o f Psycho logy , K ash i V idy ap ee th , V aranasi, andthe D epartm en t o f M ed ica l E ndocrino lo gy , S an jay G andh i P ost G radua teIns titu te of M edical S cience s, L ucknow , Ind ia .

2 Suppo rted by gran t 5 /4 -4 /18(M ) N CD -I(870 6390 ) of the Ind ian Coun-cil o f M edic al R ese arch , N ew Delh i.

3 A dd ress rep rin t req ue sts to M M Godbole , A ssociate P rofe sso r, D ep art-m ent of M ed ica l E ndo crin o logy , S an jay G andh i P os t G radua te In stitu te oM edic al S cience s, Lu cknow 226014 , Ind ia .

R eceived A p ril 27 , 199 5 .A ccep ted fo r pub lica tion Jan uary 1 9 , 1 996 .

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M O TIV A T IO N A N D LEA RN IN G IN IO D IN E -D EFIC IEN T CH ILD REN 78 3

ever, b iochem ical eva lu ation o f the con tro l g roup su ggestedm ild iod in e deficiency (M ID ) . B o th S ID and M ID villag esw ere s itu a ted a t an av erag e d istance of 6 km from the tow n ofP ad rauna . C u ltu ra l indexes such as d ia lec ts, expo sure to cu l-tu ra l even ts su ch as w eek ly m arke ts and ru ral dance and dram apro gram s, an d partic ipa tion in re lig ious fes tiva ls w ere fou nd tobe s im ila r in bo th S ID and M ID v illages .

In itia lly , 3 40 go itrous m ale ch ild ren aged 8-18 y w ere se lec tedfrom th e SD villages . C re tin s w ere ex clu ded from the s tudy .In itia l se lec tion w as b ased on soc io eco nom ic s ta tus (SES) ra tingscores (w hich m easu red n ine com ponen ts o f depriva tion : h ous in gco nd itio ns, hom e env ironm ent, econom ic suffic iency , n u trition ,clo th ing , fo rm al ed uca tion al experiences, pa ren ta l charac te ristic s,t ravel and rec rea tio n , and m isce llan eo us com ponen ts) w ith in theran ge of 80-1 1 0 (9 ). O f these , 160 w ere se lec ted fo rhi s s tudybecause of the ir fo rm al edu ca tiona l ex perien ce , w hich w as aprerequ isite fo r assessm en t o f m o tiva tion to ach ieve . F orm al ed-uca tio n , as d efin ed , inc luded th e ab ility to read , w rite , and com -prehend . F ina lly , 1 00 ch ild ren (50 aged 9-12 y and 50 aged 12-15y) w ere selecte d as the 5ff) g roup . T he rem ain in g 60 ch ild renw ere ex clud ed b ecause they d id no t know the ir ex ac t age . O n ehund red age-m atch ed ch ild ren from M ID v illages w ere se lected asth e con tro l sub jec ts . T he SW ) and M ID gro ups w ere m atched fo rSE S [t (198) = 1 .33 , P > 0 .05 , NS ] and fo rm al educa tiona lexper ience [t (198) = 1.90 , P > 0 .05 , N S] . In the 9-l2 -y -o ldgroup from the end em ic v illages, 10 (20% ) sub jec ts had go ite rg rade Ia, w hereas 4 0 (80% ) had go ite r g rade lb . In the2-15-y -o ld g roup , 15 (30% ), 3 1 (6 2% ), and 4 (8% ) sub jec ts had go ite rs o fg rade Ia , Ib , and II , resp ec tive ly . In vestiga to rs w ere b linded to theiden tity o f the grou p to w hich the sub jec ts b elon ged . T he s tudyp ro toco l w as approved by the E th ica l C om m ittee of th e Ind ianC ounc il o f M edica l R esearch . In fo rm ed con sen t w as ob ta inedfrom the ch ild ren s p aren ts befo re th etar t of th e s tu dy .B io ch em ica l ana ly sis

The m agn itude o f iod in e defic ien cy in SID and M ID grou psof sub jec ts w as ascertained by b iochem ica l ana lys is o f u rineand b lood sam ples co llec ted from one-th ird of the to ta l sub -jects , w ho w ere rand om ly se lec ted . T h e u rina ry excre tion o fiod ine w as d ete rm ined by th e m ethod of d ry ash ing (10) andserum thyro x ine (norm al ran ge in our labo ra to ry : 70-1 70nm ol/L ) an d thy ro id-s tim ula ting horm one (TSH ) (n orm alrange : 0 .30-5 .0 m U lL ) by rad io im m unoassay u sing a k it fromBA RC , Bom bay . T he urina ry excre tio n of io d ine (219 .84 57 .52 and 449 .14 32 .31 nm ollL fo r S ID and M ID group s,respec t ive ly , P < 0 .0 01) and serum thyrox ine (90 .36 6 .46and 123 .70 15 .42 nm ollL , respec tive ly , P < 0 .0 01) w assign if ican tly less in the SID group than in the M ID grou p .Serum TSH w as sign if ican tly h igh er in the S ID group th an inthe M ID group (6 .2 3 0 .34 an d 4 .85 0 .28 m U lL , resp ec-t ive ly , P < 0 .01) . U rina ry iod ine excre tion and TSH sugges tedtha t by in te rn ationa l s tan dards our M ID sub jec ts w ere m ild lyiod ine-defic ien t and m ay a lso have h ad subc lin ica l h ypo thy -ro id ism.

L earn in g m a ter ia lsHuman sty lus m aze

B lindfo ld ed su b jects w ere tested by us in g a h um an sty lusm aze p atte rn h av in g o ne th ro ugh-p a th and som e blin d a lley s.S ub jec ts w ere req u ired to learn the correc t th rou gh-pa th from

sta rtin g poin t to go al w ith a m eta l s ty lus th rou gh 10 lea rn in gtrials . T he num ber of e rro rs an d tim e tak en in seco nds to reachthe g oa l po in t w ere recorded . L earn ing w as ref lec ted by ip rovem ent in perfo rm ance over trials . W e used th e m odifiedversion of th e tes t tha t has b een u sed ex tensive ly (1 1 , 12 ) .Verb a l learn ing

The verb al learn ing tes t w as a m odified vers ion of one useearlie r (1 1). Tw o separa te lis ts o f vern acu la r (H ind i) w ords,each co n tain ing 1 5 item s (w ords), th ree from each of the fivecon cep tu al ca tegor ies (an im al, fru it, vege tab le, ce rea ls , au tens ils) w ere p rep ared . T he selec tio n of these w ords wb ased o n fam ilia rity calib ra tion of a large num ber of w ordsW ords o f a m odera te d egree of fam ilia rity w ere used inpresen t study . T he item s w ere pr in ted on 3- by 5-inch (8 -13-cm ) card s. T he cards w ere g iven a fixed sequence such thno tw o w ords o f th e sam e ca tegory appeared ad jacen tly . Tsequ ences w ere arranged in tw o lis ts : A fo r lea rn ingfree -reca ll m eth od and B fo r lea rn ing b y seria l-reca llme t h o d .

In the f ree- reca ll m ethod of lea rn ing , item s w ere presen tedora lly one by one to sub jec t a t a speed of one item p er s .W hen the w hole list w as p resen ted , th e sub jec t w as ins truc tedto reca ll th e item s in any order h e liked . T he correc t reca llw ere recorded . T h is cons titu ted o ne tria l o f lea rn ing . T en su ctrials w ere g iven in a ll. In th e se ria l- reca ll m etho d of learn ing ,th e sub jec t w as requ ired to recall the item s in the sequencew hich th ey w ere presen ted .

Pic tor ia l learn ingTw enty b lack-an d-w hite p ho tograp hs (5 5 m m X 45 m m ) of

boys al l appro x im ate ly the sam e ag e w ith un ifo rm dress ann eu tral fac ia l ex press ions w ith m odera te iden tifiab ility w ep rep ared . T he stim uli w ere ran dom ly d iv ided in to tw o g roups :the o ld group and the new gro up , each co n ta in in g 10 pho tog rap hs. F ive lea rn ing tria ls w ere g iven to each sub jec t. In eactria l, a sub jec t w as show n the o ld group o f 10 pho tog raphs oafte r the o th er, each fo r a dura tion o f 3 s. T hen these ph o tograph s w ere m ixed and sh uffled w ith the 10 pho tog raphs ofnew gro up an d the sub jec t w as ask ed to iden tify th ose pho tograph s tha t w ere show n to h im p rev iously . F ive such lea rn ingtria ls w ere run . T h e num ber of correc t recogn ition s in each trw as recorded . P ic to ria l lea rn ing w as re flected in the increas in gnum ber of co rrec t recog n itio ns ov er tria ls .

Ach iev em en t m otiva t ion sca leTh is sca le pu rports to m easure the fee ling of com petence an

w orth , tendency to ach iev e success, and sense of s triv ingsup erio r perfo rm ance in schoo l and o ther p hases o f life . It a lm easures persev eran ce , risk -tak ing ab ility , ta sk -o rien tin gpro ach , and be lie f in hard w ork . T h is sca le (1 1 , 14 ) con sists16 yes-o r-no item s w ith a h igh degree o f tes t- re tes t re liab ility(0 .79) and in te rna l co nsis ten cy (0 .81). It is su itab le fo r assess -ing m otiva tio n to ach ieve on ly fo r those ch ild ren w ho are g o ingto sch oo l an d can read and unders tan d the item s.

StatisticsThe effec ts o f io d ine d ef ic iency , age , and prac tice tria ls a

the ir in te rac tion w ere ascertain ed by 2 (iod ine d ef ic iency) X 2(age) X 10 (tria ls ) trend ana lysis o f variance w ith repea ted

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78 4 T IW A R I ET A Lm easures . T he da ta fo r p icto r ia l lea rn ing w ere an alyzed sim i-la rly w ith five leve ls o f tr ia l va riab le. T he da ta fo r ach ievem entm otiva tio n w ere ana ly zed by 2 (iod ine defic iency) X 2 (ag e)ana lys is o f varian ce .

RESULTS

M aze learningS ID ch ild ren com m itted s ign ifican tly m ore er ro rs in m aze

lea rn ing than d id the ir M ID coun te rp arts (F111961 - 170 .36 , P< 0 .01 ). T he in itia l pe rfo rm ance of the o lder g roup w as be tte rthan th a t o f the y ounger g roup (F11 ,1961 = 200 .15 , P < 0 .01) ,b u t the ra te o f redu ction in erro rs w as s ig n ifican tly g rea ter inthe yo unger ch ild ren (F1917 1 = 88 .81 , P < 0 .01 ) (F igure 1).

S ID ch ild ren took sign if ican tly m o re tim e to lea rn the m azethan d id the M ID child ren (F131961 = 64 .61 , P < 0 .01 ). H erea lso , o lde r ch ild ren took less tim e to lea rnF11 1 9 6 1 = 310 .83 ,P < 0 .01), bu t the ra te o f im p rovem ent in the speed o f lea rn in gw as grea te r in yo unger ch ild ren (FI917MI = 65 .45 , P < 0 .01)(Figure 2).

V erbal learningThe effect o f iod in e d ef ic iency on verba l lea rn ing by the

free -recall m ethod w as no t sign if ican t. F ree reca ll, be ing a lessdem and ing task , d id n o t d isc rim ina te be tw een SD and M IDchild ren of any age . T he resu lts o f se ria l lea rn in g ag ain show edth a t S ID ch ild ren are s low er lea rners (F111961 = 64 .45 , P