The Components of Imitation
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TheComponentsofImitation Onefunctionthatinvolvesstructuresintwocerebralhemispheres December22,2015 Welearnmanythingsthroughimitation:howtowalk,playaninstument,sports,andevenmore. Whataretheprocessesinthebrainresponsibleforimitation?Forsomeyearsnow,sciencehas beenexaminingtheroleofmirrorneurons,butthereisstillmuchtounderstand.Onestudy focusingonneurologicalpatientsshowedthatatleasttwocomponentsareinvolvedinimitating gestures,eachfromadifferenthemisphereofthebrain.Thestudy,whichSISSAparticipatedin, waspublishedinNeuropsychologia Afterabraininjury(causedbystrokeorhemorrhage,forexample),patientsmayhavedifficulty imitatinggesturesandmovementsofothers(ideomotorapraxia).Inthehistoryof neuropsychology,thesestudiesareamongthebestknown(thefirstdatebacktotheearly1900’s) asthesedeficitshindertherapyaimedatrecoveringmotorskills,sincethepatientcannot performgesturesbyimitatingthedoctor.Inthelasttwentyyears,thesestudieshavefoundnew significancethankstothediscoveryofmirrorneurons,andyetlittleisknownaboutthese processes.Manyscientiststhinkthelefthemisphereplaysadominantrolebecausethisproblem mostoftensurfacesincasesofunilateralbrain-damageofthelefthemisphere.Howthen,canwe explainthesmallpercentageofapraxicpatientswhohavesufferedunilaterallesionstotheright hemisphere? PaolaMengotti,atSISSAatthetimeofthestudy,nowatForschungszentrumJülichinGermany, SISSAProfessorandHeadoftheiNSuLaLaboratory(NeuroscienceandSociety),Raffaella Rumiati,andcolleaguesconductedastudytoanswerthisquestion.Twentypatients(visitedat SanCamilloinVeniceandAziendaOspedaliero-UniversitariaOspedaliRiunitiinTrieste)with unilateralbrainlesionsintheleftorrighthemispheres,plusacontrolgroupparticipatedinthe study.Theinitialideawasthatimitationismadeupofatleasttwodistincttasks:motorimitation, andaspatialcomponent.Whenwehavetoimitatesomeoneelse’smovements,wenotonlyhave torepeattheactions,butwealsohavetotranslatethemtoourbody(mirrorthem).Inthestudy, patientsperformedimitationtasksusingoneofthetwocomponents,motororspatial. Performanceforeachcomponentwasthencomparedandcategorizedinrelationtothetypeof lesion. Whatemergedisthatwhatcountsinimitationisthesimilaritybetweenwhatisseenandwhatis produced,andthisofcoursedependsontheindividualtypeofdeficit."Analyzingthe performanceoftwoimitationtasksbypatientswithlesionsintherighthemisphereandtheleft hemisphere,wewereabletodemonstratethatimitationisbasedonthesimilaritybetweenthe observedactionandtheoneproduced,"explainsRumiati."Thissimilarityreflectseitheran anatomicalmatchoraspatialone.Lesionsinthelefthemisphereaffecttheformerwhilelesions intherighthemisphereaffectthelatter." USEFULLINKS: • OriginalpaperonNeuropsychologia:http://goo.gl/DjV6QG IMAGE: • Credits:JamieMcCaffrey(Flickr:https://goo.gl/5XffDR) Contacts: Pressoffice: pressoffice@sissa.it Tel:(+39)0403787644|(+39)366-3677586 viaBonomea,265 34136Trieste MoreinformationaboutSISSA:www.sissa.it
