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Challenging the estimation of cortical activity from MEG with simulated fMRI-constrained retinotopic maps.

Alexandre Gramfort 1, 2 Benoit Cottereau 3 Maureen Clerc 2 Bertrand Thirion 1, 4 Sylvain Baillet 3
1 PARIETAL - Modelling brain structure, function and variability based on high-field MRI data
Inria Saclay - Ile de France, NEUROSPIN - Service NEUROSPIN
2 ODYSSEE - Computer and biological vision
DI-ENS - Département d'informatique de l'École normale supérieure, CRISAM - Inria Sophia Antipolis - Méditerranée , ENS Paris - École normale supérieure - Paris, Inria Paris-Rocquencourt, ENPC - École des Ponts ParisTech
Abstract : Detection of activity from the primary visual cortex is a difficult challenge to magneto-encephalography (MEG) source imaging techniques: the geometry of the visual cortex is intricate, with structured visual field maps extending deeper along the calcarine fissure. This questions the very sensitivity of MEG to the corresponding neural responses of visual stimuli and the usage of MEG source imaging for innovative retinotopic explorations. In this context, we compare two imaging models of MEG generators in realistic simulations of activations within the visual cortex. Localization and spatial extent of neural activity in the visual cortex were extracted from retinotopic maps obtained in fMRI. We prove that the suggested approaches are robust and succeed in accurately recovering the activation patterns with satisfactory match with fMRI results. These results suggest that fast retinotopic exploration of the visual cortex could be obtained from MEG as a complementary alternative to more standard fMRI approaches. The excellent time resolution of MEG imaging further opens interesting perspectives on the temporal and spectral processes sustained by the human visual system.
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Submitted on : Thursday, July 15, 2010 - 2:59:36 PM
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Alexandre Gramfort, Benoit Cottereau, Maureen Clerc, Bertrand Thirion, Sylvain Baillet. Challenging the estimation of cortical activity from MEG with simulated fMRI-constrained retinotopic maps.. Conference proceedings : .. Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, Institute of Electrical and Electronics Engineers (IEEE), 2007, 2007, pp.4945-8. ⟨10.1109/IEMBS.2007.4353450⟩. ⟨inria-00502698⟩



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