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Valdis Gudmundsdottir, Ph.D.student

by Valdis Gudmundsdottir last modified 2009-11-03 19:06

Neurospin | Institut d'Imagerie BioMédicale
Commissariat à l'Energie Atomique
145, Point Courrier 156
91191 91191
Phone: + 33 1 69 08 78 35

Valdis Gudmundsdottir PhD Student is currently employed as a Marie Curie doctoral fellow (EVAN Training Network). She is a PhD student working on the applications of paleoanthropological methods for the study of the human cortex under the scientific direction of Jean-Francois Mangin.

The objective of this thesis is the transfer of morphometric methods from paleo-anthropology towards neuroimaging.

One of the key differeces between the two fields of study is the number of specimens one works with. A paleo-anthropologist will typically work with relatively few specimens while in neuroscience a database can easily comprise 100 brains. The paleo-anthropologist can place the landmarks manually on the surface of their specimen while in neuroimaging a method must be devised to place landmarks automatically on the cortex.

The host institution, Neurospin, has developped a method to automatically recognise the cortical folds. See figure 1 (a-b). Their extremities and centres of gravity are then calculated and used as landmarks for a geometric morphometric analysis. See figure 1 (c-d).

The ensemble of landmarks for 62 subjects that are submitted to the shape analysis can be seen in the figure 1 (e-f).

Using these landmarks, we have compared the shape of the right and left hemispheres and have been able to identify the large mode of asymmetry in the human cortex where due to language being commonly lateralised to the left side of the brain, the posterior end of the sylvian fissure is shifted backwards in the left hemisphere. We validated the method on a manually labelled dataset seen on the left in figure 2 and then applied the method to a completely automatically labelled dataset, seen on the right hand side of figure 2. The arrows show well the global asymmetry effect at the posterior end of the sylvian fissure.

Having validated the method on a known shape effect in the brain we will now apply the method to look for early signs of psychiatric syndroms.