Studiesusingsemanticprimingparadigmstomeasuretheintegrityofthefeaturesunderlyingconcepts
in semanticdementia(SD)reporteddifferentialimpairment,inthatfunctionalfeaturesappearedtobe
more robusttobraindamagethanotherfeatures,suchasperceptualones.However,thesepriorstudies
weresinglecasereportsandtheinclusionoftoomanyheterogeneousfeaturesunderthe “functional
features” heading
... [Show full abstract] castsdoubtsontheirapparentpreservation.Toverifytherobustnessoffunctional
features comparedwithperceptualones,wecarriedoutagroupstudywherewedeliberatelyrestricted
the explorationofsemanticfeaturestotwoclearlydefined typesofattribute:visuoperceptual(“visual”)
versus contextual–functional (“contextual”).Weadministeredanimplicitlexical-decisionprimingtaskto
8 SDpatientsand31healthymatchedcontrols,atbaseline.Fourofthepatientsunderwentafollow-up
assessment atoneyear.Forcontrols,wefoundasignificant primingeffectinthevisualcondition,butnot
in thecontextualone,whereastheSDgroupexhibitedthereversepatternofperformances.Thefollow-
up dataprovidedevidenceoftherobustnessofthedissociationbetweenprimingperformancesinthe
two attributeconditions.ThefactthataparticularprimingeffectwasobservedintheSDpatientsbutnot
in controlscouldberegardedasasignofsemanticdisequilibrium.Sinceperceptualfeatureshavebeen
shown tobeacoredeterminantofsimilarity-based/taxonomicrelationships,whereascomplementary-
based/thematic processingreliesmainlyoncontextualrelationships,weinterpretedour findings in
terms ofthedifferentialrecruitmentofoneofthetwosystemsofsemanticrelationships(taxonomicvs.
thematic). Moreover,thesetwodistinctandparallelsystemshavepreviouslybeenreportedtocoexist –
and compete – in healthyadults.Wethusarguethatcontrolsautomaticallydrewonsimilarity-based/
taxonomicrelationships,leadingtoasignificant primingeffectforvisualfeaturesbutnotforcontextual
ones. Bycontrast,theirimpairedperceptualfeaturesforcedtheSDpatientstoresorttothesystemof
thematic relationships.