Cartographie fonctionnelle cérébrale chez la souris et l`homme

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Cartographiefonctionnellecérébralechezla
sourisetl’homme
FacultédeMédecine,UniversitédeGenève
Coursàoption2ème‐3ème années
«Duneuroneaupatient »(Prof.J.Z.Kiss,Neuroclub)
[email protected]
FunctionalBrain
MappingLab neuroclub.unige.ch
Cartographie fonctionnelle cérébrale chez la souris et l’homme
Plan
1) Historicalintroductiontofunctionalbrainsystems,theexampleoflanguage
2) Introductiontoneuronalnetworks
3) Investigatingfunctionalbrainsystemsandneuronalnetworks:
+Exampleofapplication:Rehabilitationofprosopagnosia,presentedbyNicolasBurra
(Neuroclub)
4) Whyusingtheanimalmodel?

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a.The"prehistory"ofbrain functions:localization ofthemind…
‐During early antiquity,various functions attributed tothebrain (i.e.Aristotle:cooling mechanism
fortheblood;Platonalready proposed it forthelocatio oftheimmortal soul)
1.Historicalintroductiontofunctionalbrainsystems
‐Then romanphysician Galen localized mentalactivity inthebrain based onbrain injuries
observations
‐Descarteslocated thesoultothepineal gland(endocrinegland,butat leastit’s partofthebrain)
b.Thehistory ofbrain‐mind relationships:globalism VSlocalizationism
Globalism:
M.Rolando(1809)andM.J.P.Flourens (1824)madelesionsintheCNS
ofanimalsandstudiedtheresults:
1. Nerves,spinalcordandmedullaoblongata:directlyexcitemuscles.
2. Cerebellum:coordinationofmovements
3. Hemispheres:initiatethevoluntarymovements
“Lenerf excite;lamoelle épinière lie;lecervelet coordonne;leslobes
cérébraux veulent etsentent.“
Howeverwithinthehemispherestheyfoundnosingleregion
responsibleformemoryorcognition!
Cognitivefunctionsaregloballydistributedovertheentirecortex=
Globalism
Localizationism:
FranzJosephGall (1758‐1828),JohannSpurzheim (1776‐1832),Paul
PierreBroca (1824‐1880)
Coginitive functions are localized to specific brain centers,cortical
areas inparticular

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c.Theexample ofspoken language
PaulPierreBroca(1824‐1880)
CarlWernicke(1848‐1905)
Inorder tocommunicate orally:
‐Hearing sounds
‐From sounds towords (sensory uncoding)
‐From words toconcepts(meaning)
‐From meaning towords
‐From words tospeechmovements (motor planning)
‐Motor controlofphonatory apparatus
Broca’s aphasia
In~1860,Brocareported apatient,M.Leborgne ("Tan")
Broca’s aphasia:inability toproduce speech;understanding notmassively impaired
Wernicke’s aphasia (~1875)
Notalllanguage deficits areduetolesions inBroca’s area
Wernicke’s aphasia:inability tounderstand speech;speechproductionis possiblebutparaphasias,
speechmay be meaningless

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Conductionaphasia=adisconnection syndrome
•Notalllanguage deficits areduetolesions inthecerebral cortex
•Conductionaphasia:inability torepeat speechdirectly,understanding unimpaired,production
impaired with autocorrections
•Interruptionoffibrepathway:disconnection syndrome
Theexample oflanguage:conclusion
Language
requires
the
integrity
of
several
cortical areas
anatomically
and
functionally
linked
Language
requires
the
integrity
of
several
cortical
areas
,
anatomically
and
functionally
linked
together. Purelocalisationism is notenough toexplain brain functions.
Thisexample introduces several importantconcepts:
•Regional specialization,functional andstructural
•Serialandparallel processing
•Lateralization
d.Brodmann’s cytoarchitectonic map (~1900)
Brodmann classified corticalregions infunction oftheir histology.
Some areal delimitations aresimilar totheanatomic regions lesioned inBroca’s andWernicke’s
patients
Thecortexcan be divided inareasofspecific structuresandfunctions.
Korbinian Broadman (1868-1918)

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2.Introductiontoneuronalnetworks
•Corticalneurons haveanhorizontalandverticalorganization:they
areorganized in layers andinminicolumns .
•Aminicolumn is abasiccorticalnetworkcontaining 100‐200
neurons (excitatory andinhibitory,localandprojecting)="Building
block"formorespecialized,morediversecorticalmacrocolumns
•Minicolomns organize inmacrocolumns:50‐100minicolumns.
Neurons inthesame macrocolumn share functional properties
e.g.inprimary cortices:
‐Neurons inamacrocolumn respond tosimilar stimulus
localizations andproperties
‐Neighboring macrocolumns "represent"neighboring regions of
theperiphery (topological correspondence)
Thus,corticalneurons organize innetworksat different scales:
‐Corticalminicolumns
‐Corticalmacrocolumns
‐Localcorticalareanetworks
‐Andfinally inlarge‐scale neuronalnetworks
•Finally,large‐scale neuronalnetworksaremadeupfrom several localcorticalareanetworks
interconnected bylong‐rangeprojections
•Function together inallcorticalfunctions
•Thenetworking ofdiscrete corticalareasinto large‐scale networksis dynamic (e.g.understanding
written andspoken language engagepartially overlapping networks)
Completevisualnetworksinthemacaquebrain(FellemanandVanEssen,1990)Simplifiedlanguagenetwork