Interdisciplinary Workshop on3D Paleo-Anthropology, Anatomy, Computer Science & Engineering

- Synergies for the Future -June, 19-20 – Musée de Toulouse, France

What we can infer by comparing the shape of anatomical structures?Comparative anatomy of the parietal cortex in human and chimpanzee

E.P. Gilissen1, M. Suliga2, R. Deklerck2, E. Nyssen2, R. Achten3,J.M. Erwin4, P.R. Hof5, C.C. Sherwood6

1Musée Royal de l’Afrique Centrale et Université Libre de Bruxelles,2Vrije Universiteit Brussel, 3Gent Universiteit, Belgique

4McDaniel College, Maryland, Foundation for Comparative andConservation Biology, Pennsylvania

5Mount Sinai School of Medicine, New York Consortium in Evolutionary Primatology,New York

6The George Washington University, Washington DC, USA

Why cortical folding?

Simple mechanistic hypothesis:

The functional necessity for cortical folding

=packing the extended cortical

surface into the restrictedvolume of the cranial vault

(Welker, 1990)

(Gorilla gorilla beringei, F)

Cortical folding andconnectivity optimization(Innocenti, 1990)

Frontal sections showingcallosal connections(injection sites)

(A) rat(Heimer et al. 1967)

(B) rhesus macaque(Goldman-Rakic, 1982)

This illustrates howgyration can shortenthe trajectory ofcortico-cortical axons

Tension-mediatedfolding of cerebralcortex(Van Essen, 1997)

The simple mechanistic hypothesisis only a very partial explanationof cortical folding…

In the early enucleate monkey,the large changes in the dimensionsof striate and extrastriate cortexdisrupt the appropriate topographicalrelationship between cortical surfaces,which, in turn, may generate theunusual gyral pattern in these animals

Gyri formation serves largelyto accommodate cortical connectivity

Cortical folding andcortical areas

…cortical folds are much betterpredictors of the cortical areasthan had been previously thought

…results suggest a commonmechanism for the developmentof the cortical folds andthe cytoarchitectonic fields

connectivity optimization andcortical areas

Organization of cortical areashas evolved to optimizeInterareal connections

Cortical folding

Onset of connectivityConnectivity optimization

Positioning ofcortical areas

…patterns ofasymmetry in gyrificationresemble the right frontal,left occipital asymmetriesin cerebral torque

…asymmetries in bothcerebral torque and gyrificationmay reflect a common neural developmental patternof the cortex

Positioning ofcortical areas

Brain surface shape

Cortical folding

Onset of connectivityConnectivity optimization

Cortical surface viewing

Native 3D

Smoothed

Ellipsoid

Slices6mm slabs

Flat map

“Flat maps are the most compact representation because the entire hemisphere can be seen in a single view, and they have no foreshortening because the surface is planar. However, flat maps do entail the introduction of selected cuts to prevent severe distortions in surface area.”

A METHOD TO CONSTRUCT FLAT MAPSOF THE BRAIN'S SURFACE AND ITS

APPLICATION

Rudi DeklerckDept. ETRO-IRIS, IBBT, Vrije Universiteit

Brussel, Pleinlaan 2, 1050 Brussels, Belgiumrpdekler@etro.vub.ac.be

Junfeng Guo, Alexandru Salomie, Marek Suliga, Edgard Nyssen, Liu Tao, Danielle

Baleriaux, Jan Cornelis

A coarse mesh is defined on a gridcorresponding to two hemi-ellipsoid

Distance homogenization

Examples of meshesduring the deformation

Obtention of a smooth high-resolution surface

« flat » cortical surface

Sulci identification

Viewing the cortical surface with TeDiMedIA software

Central sulcus

Postcentral sulcus

Central sulcus

Postcentral sulcus

« flat » cortical surface andoblique section

« flat » cortical surface and3D reconstruction

Pan troglodytes

RB 11 (Pan)-7659

This research was supportedby the “Paul Broca II – The evolution of cerebral

asymmetry in Homo sapiens” project6th Framework of the European Community