Generation of language in normal males : a regional cerebral blood flow study

173 Pages·1992·5.3 MB·English

by  Williamson, David James Graves

GEANERREAGTIIOONNALOFCELRAENBGRUAALGBELOINODNOFRLMOAWLSTMUADLYES:
By
DAVIDIAMESGRAVESWILLIAMSON
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUONFITVHEERSRIETQYUIORFEFMLEONRTISDFAOIRNTPHAERTDIEAGLREFEULOFFILLMENT
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
1992
Copyright1992
by
DavidJamesGravesWilliamson
ACKNOWLEDGEMENTS
IwishtoexpressmysincerestthankstoDr.BruceCrossonandDr.StephenNadeaufortheir
invaluablesupportandguidancethroughoutthisproject.IalsowishtoexpressmythankstoDr.
KennethHeilman,Dr.LeslieGonzalezRothi,Dr.EileenFennell,andDr.RussellBauerforinvaluable
helpwiththedesignofthestudy,andtoDr.ShailendraShukla,Dr.ClydeWilliams,andDr.Michael
Fagenfortheirtechnicalsupportofthisproject.SpecialthanksgotoMorrisThompsonwhose
patienceandflexibilitywascrucialtothecompletionofthisstudy.ThanksalsogoestoRandi
Lincolnforherhelpwithsubjectscreening,andIamindebtedtoJaniceHoneymanforher
programmingskills.IamappreciativetoDr.JamesScottforhissupportandconstructivecriticismas
well.1alsowishtoexpressmyappreciationtomywifeLinda,whoprovidessupportforallmy
endeavorsaswellasthebestsoundingboardforconceptualandstatisticaldilemmasthatIcouldhope
for.Finally,Iwouldliketoacknowledgemyparents,JamesandBarbaraWilliamson,forthesupport
andencouragementtheyhavecontinuedtoprovidemeovertheyears.
iii
TABLEOFCONTENTS
page
ACKNOWLEDGEMENTS »>
ABSTRACT vi
CHAPTERS
I INTRODUCTION 1
DMeeftihnoidtoiloongiocfalTCeornmsisderations 24
II REVIEWOFTHELITERATURE 17
III MATERIALSANDMETHODS 71
PPPPiiirllliooomtttaSSSrtttyuuuSdddtyyyu###d132y 77781426
IV RESULTS 93
DInavteasAtniaglayttiiocnStorfatCeoggynitiveEffort 9935
TestsofHypotheses 95
V DISCUSSIONANDCONCLUSIONS 107
APPENDICES
A DIRECTIONSTOSUBJECTSINPILOT#2 119
B RATINGSOFTHEIMAGEABILITYANDCONCRETENESSOF246VERBS.... 121
C INSTRUCTIONSFORPILOTSTUDY#3 124
D INSTRUCTIONSTOEXPERIMENTERANDSUBJECTFORMAINSTUDY
COGNITIVESTIMULATION 127
E EXPERIMENTALSTIMULI 140
F CORREIRLNAADTTIIICNOEGNSSO(FBREEDATICFWTFEIIECONUNLATTDIYJM)UEWSITTTOEHDNIONRVEAEGNILDOSNATACILRMUOCLSOISUNACTNOSNDDASINUTBDIJOEENFCSFTOIVRET 144
G SCATTERPLOTSOFREGIONSOFINTERESTBYSIDEANDTASK 145
H PARTIALCORRELATIONS(CONTROLLINGFORGLOBALCOUNTS)
BETWEENREGIONS 150
REFERENCES 154
BIOGRAPHICALSKETCH 163
AbUsntirvaecrtsiotfythoefDFilsosreirdtaatiinonPaPrrtieaslenFtueldfitlolmtehnetGroafdtuhaeteReSqcuhioroelmeonfttshe
fortheDegreeofDoctorofPhilosophy
THEGAERNEEGRIAOTNIAOLNCOEFRELBARNAGLUBALGOEOIDNFNLOORWMSATLUMDAYLES:
By
DavidJamesGravesWilliamson
December,1992
Chairman:BruceCrosson,Ph.D.
MajorDepartment:ClinicalandHealthPsychology
Thisinvestigationexaminedregionalcerebralbloodflowduringthegenerationoflanguage.
Twelveneurologicallynormalright-handedmalesparticipatedinthisstudy.Subjectsperformed
threecognitiveactivationtasks,alterwhichdistributionofregionalcerebralbloodflowwas
determinedviasinglephotonemissioncomputerizedtomography(SPECT).Thethreetaskswere
designedtopreferentiallystressthephonological,semantic,andgrammaticalcomponentsof
languageinastepwise,hierarchicalfashion.Imageanalysiswasperformedusinganeuroanatomical
atlasandamagnedcresonancescanofeachsubject'sbraininconjunctionwiththedatagivenbythe
SPECTscans.
Intertaskanalysessuggestanimportantrolefortheleftposteriorsuperiortemporalregion
(i.e.,Wernicke'sarea)intasksstressingthegenerationoflexical-semanticinformation.Inaddition,
intrataskanalysessuggestthatwhiletherearenodifferencesinwhole-braincountsacrosstasks,each
taskdoesengenderadistinctpatternofasymmetriesbetweenareahomologues.Inparticular,the
findingssupporttheroleofWernicke'sareainlexical-semanticprocessingandprovidefurther
supportforthepreviouslyreportedfindingsofconsistentleftfrontalopercularinvolvementin
generativelanguageandleftBrodmann'sarea37intasksrequiringvisualanalysisofwordforms.In
addition,resultsareconsistentwiththeviewthatpracticeofagivenactivationtaskmaychangethe
magnitudeandpatternofrCBFobservedduringthesubsequentperformanceofthattask.Theresults
arediscussedinlightofcurrentfindingsinthefunctionalneuroimagingandlesionliterature,and
directionsforfutureresearcharediscussed.Thisinvestigationreinforcesthemeritsofstudyingthe
neuralinstantiationoflanguageinthehumanbrainwithfunctionalneuroimaging.
vii
CHAPTERI
INTRODUCTION
Thestudyoflanguagehasarichhistory,fromtheseminalclinico-anatomicalcorrelationof
PaulBrocain1861tothefunctionalneuroimagingstudiesoftoday(Wise,Hadar,Howard,&
Patterson,1991).Themostfruitfuloftheseeffortshavebeenbuiltuponcarefulconsiderationofthe
observedlanguagephenomenaandsystematicinvestigationofthe"buildingblocks"uponwhichthese
phenomenaarebased.Foralmostonehundredyears,theseeffortswerelimitedtoobservationsof
patientswithbrainpathologythatcouldnotbequantifieduntilautopsy.Despitetheselimitations,
theoristssuchasWernickeandLichteimwereabletogenerateageneralframeworkforthe
instantiationoflanguageinthebrainwhichhasheldupwelltothetestoftime(Lichteim,1885;
Wernicke,1874).Evolvingtechnologiesandtherediscoveryandelaborationofthesetheoriesby
Geschwindinthelate1960'susheredinanewageoflanguageinvestigation(Geschwind,1972).The
richcomplexityofboththeneuroanatomicalandpsycholinguisticcomponentsoflanguagehassparked
theinterestofavarietyofdisciplines,andtheincreasinginter-relianceofcognitive,psycholinguistic,
neuroanatomical,andneurophysiologicalinvestigationsuponeachotherhasthepotentialtoprovidea
morecomprehensiveunderstandingoflanguagethanhasbeenavailabletopreviousgenerations.
Investigationsbuiltuponthetheoreticalfoundationslaiddownbypreviousgenerationswhichexploit
thecapabilitiesprovidedbytechnologicaladvanceswillbeanimportantcomponenttothefurther
investigationofthe"buildingblocks"oflanguageinanormalpopulation.Thefocusofthecurrent
studyisanexaminationofspecificcomponentsoflanguagecomprehensionandgenerationutilizing
functionalneuroimaging.
DefinitionofTerms
Acarefulexaminationoflanguagerequiresanexplicitdefinitionofthephenomenatobe
investigated.Forthepurposesofthisstudy,languagewillbebrokendownintothreecomponents:
phonology,lexical-semantics,andgrammar.Forthepurposesofthisstudy,phonologicalprocesses
willbedefinedasthosethatdealwiththesequencingofindividualphonemesintomorphemes,which
arethenusedtoformwords.Otherphonologicalprocesses(e.g.linguisticprosody,accent)arenot
explicitlyaddressedinthisstudy.Lexical-semanticprocessesarethosethatdealwithmeaningful
conceptsandthesymbolicrepresentationofthoseconcepts(i.e.words).Specifically,lexicalprocesses
dealwithwords,whilesemanticprocessesdealwithconceptualknowledge.Whiletheseprocesses
havebeenshowntodissociate(Hillis&Caramazza,1991),thecurrentstudymakesnoattemptto
investigatethisdissociation.Grammaticalprocessesdealwiththeword-andsentence-levelaspectsof
languagewhichareusedtoconceptuallyelaborateuponsinglewordsandtodenoterelationships
betweenwords,respectively.Atthesinglewordlevel,changesintheinflectionaland/orderivational
morphologyofthewordareusedtospecifyitsproperties.Incontrast,thesentential-levelproperties
denotetherelationshipsbetweenwords;thesepropertiesmaybereferredtoasthesyntacticproperties
ofasentence.Althoughthetermsgrammarandsyntaxhavebeenusedinterchangeablyinthe
literature,Nadeau(1988)pointsoutthatsyntacticandmorphologicalprocessesaredistinctboth
conceptuallyandanatomically.Furtherinvestigationofthedissociabilityofthesecomponentsis
beyondthescopeofthisstudy,andthetermgrammarwillbeusedtoincorporatebothsyntacticand
morphologicalprocesses.
Functionalneuroimagingstudieshavevariedagreatdealintheextenttowhichtheyhave
investigatedthesecomponentsoflanguage.Ingeneral,thecontributionsofthethreecomponentsto
theexperimentaltaskswhichhavebeenusedtoinvestigatelanguageinnormalshavebeenhopelessly
confoundedwitheachother.Whiletheseinvestigationshavebeensuccessfulinshowingthatmost
languagetasksdoengenderdifferentpatternsofregionalphysiologicalactivity(bloodfloworglucose
metabolism)thanthosethatareseenatrest,theyhavedonerelativelylittletodisambiguatethewaysin
whichdisparatepsycholinguisticprocessesareinstantiatedinthebrain.Perhapsthemostconsistent
findingtodateisthatmeasurablechangesinregionalmeasuresofactivitywilloccurduringtasksthat
requiresubjectstogeneratelanguage(Fristonetal.,1991a;Frithetal.,1991;Ingvar&Schwartz,
1974;Petersenetal.,1988;Warkentinetal.,1991;Wiseetal.,1991).Giventhesetechniques'
consistentsensitivitytogrosschangesinvolvedinthesetasks,theexperimentalmanipulationof
generativelanguagetasksmaybeapowerfulmethodofexploringtheinstantiationofdifferent
languagecomponentsinthebrain.
"Generationoflanguage"isabroadconstructwhichmaybebrokendownconceptually.The
amountof"generativecapacity"demandedforagivenlanguagetaskmaybeseentolieona
conceptualcontinuum.Thedefiningcharacteristicofthiscontinuumisthedegreetowhichnovel
formulationsoflanguagemustbeproduced.Ononeendofthecontinuumaretasksinwhichthe
materialtobegeneratedislargelypredefined.Aprimeexampleofthissortoftaskisrepetition.
Whilerepetitionundoubtedlyaccessesphonological,lexical-semantic,andgrammaticalprocesses,
onlyphonologicalprocesses(parsingofauditorystimuliintoindividualmorphemes,sequencingthese
samemorphemesforoutput,motorprogrammingofoutput)needbeintacttosuccessfullyperformthe
taskacrosstheentirerangeoflinguisticstimuli.Inadditiontothepredefinitionofgeneratedmaterial
byexternalsources,materialmaybepredefinedinternallyaswell.Anexampleofthissortof
generativetaskistheproductionof"automaticlanguage."Languageisconsideredautomatictothe
extenttowhichitcanbeproducedwithoutcognitiveeffortonthepartofthespeaker.Examples
includecounting,recitingthealphabet,orrecitingthemonthsoftheyear.Ineachoftheseexamples,
thematerialtobegeneratedisoverlearnedandexquisitelypredefined.
Taskswhichrequirenovelformulationsoflanguagevaryintheirdemandsaswell.Atask
frequentlyusedtoassessone'sabilitytoproducelanguageisalternatelytermed"verbalfluency,"
"controlledoralwordassociation,"ortheThurstonetask(Thurstone&Thurstone,1943).Invariants
ofthistask,outputisstronglymediatedbylexicalorsemanticconstraintssetupbytheexaminer,but
thesubjectisresponsibleforthegenerationofsinglewordswhichfitintotheseconstraints.External
mediationoflanguagegenerationmaybedecreasedbyaskingpatientstodescribepicturesorgenerate
storiesaroundaparticulartheme,inwhichcasethesubjectmustutilizephonological,lexical-semantic,