WASSERMANN , Demian

While predominant models of visual word form area (VWFA) function argue for its specific role in decoding written language, other accounts propose a more general role of VWFA in complex visual processing. However, a comprehensive examination of structural and functional VWFA circuits and their relationship to behavior has been missing. Here,...

The motivation of this thesis is the in vivo dissection of the human brain's white matter from diffusion magnetic resonance imaging. This procedure isolates the human brain's white matter tracts that play a role in a particular function or disorder of the brain so they can be analysed. Manually performing this task requires a great knowledge of...

We propose a new clustering algorithm. This algorithm performs clustering and manifold learning simultaneously by using a graph-theoretical approach to manifold learning. We apply this algorithm in order to cluster white matter fiber tracts obtained from Diffusion Tensor MRI (DT-MRI) through streamline tractography. Our algorithm is able...

Current theories hold that the human cortex can be subdivided in anatomically and functionally distinct regions, from which interactions cognition arises. In these interactions the long-range axonal connectivity, namely extrinsic connectivity, plays a fundamental role (Passingham et al., 2002). Hence, parceling the cortex taking into account...

Non-invasive estimation of brain microstructure features using diffusion MRI (dMRI)—known as Microstructure Imaging—has become an increasingly diverse and complicated field over the last decades. Multi-compartment (MC)-models, representing the measured diffusion signal as a linear combination of signal models of distinct tissue types, have been...

White matter pathologies such as tumors or traumatic brain injury disrupt the structure of white matter. These disruptions hamper the inference of affected pathways using tractography. A way to overcome this is to use a label fusion technique. Label fusion aims to infer the localization of the brain structure of a subject from its localization...

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White matter fiber clustering aims to get insight about anatomical structures in order to generate atlases, perform clear visualizations, and compute statistics across subjects, all important and current neuroimaging problems. In this work, we present a diffusion maps clustering method applied to diffusion MRI in order to segment complex white...

A number of non-parametrically represented High Angular Resolution Diffusion Imaging (HARDI) spherical diffusion functions have been proposed to infer more and more accurately the heterogeneous and complex tissue microarchitecture of the cerebral white-matter. These spherical functions overcome the limitation of Diffusion Tensor Imaging (DTI)...

White matter fiber clustering allows to get insight about anatomical structures in order to generate atlases, perform clear visualizations and compute statistics across subjects, all important and current neuroimaging problems. In this work, we present a Diffusion Maps clustering method applied to diffusion MRI in order to cluster and segment...

Let's suppose that we want to study specific fiber bundles in different subjects. The common approach would be to use a voxel-wise analysis like TBSS or VBM which will warp scalar volumes in a common space, e.g. MNI space, and show how every subject differentiates from an average template. However, we know that with averaging and warping much...

In diffusion MRI, the accurate description of the entire diffusion signal from sparse measurements is essential to enable the recovery of microstructural information of the white matter. The recent Mean Apparent Propagator (MAP)-MRI basis is especially well suited for this task, but the basis fitting becomes unreliable in the presence of noise....

The visual word form area (VWFA) within ventral temporal-occipital cortex (VTOC) plays a crucial role in reading, but increasing evidence points toits broader role in symbolic information processing. Consistent with this view, a recent resting-state fMRI study showed that the VWFA is strongly connected to the intraparietal sulcus (IPS) and...

The neuroscientific community today is very much interested in analyzing specific white matter bundles like the arcuate fasciculus, the corticospinal tract, or the recently discovered Aslant tract to study sex differences, lateralization and many other connectivity applications. For this reason, experts spend time manually segmenting these...

Non-invasive estimation of brain white matter microstructure features using diffusion MRI - otherwise known as Microstructure Imaging - has become an increasingly diverse and complicated field over the last decade. Multi-compartment-based models have been a popular approach to estimate these features. In this work, we present Diffusion...

We propose a novel framework to simultaneously represent the diffusion-weighted MRI (dMRI) signal over diffusion times, gradient strengths and gradient directions. Current frameworks such as the 3D Simple Harmonic Oscillator Reconstruction and Estimation basis (3D-SHORE) only represent the signal over the spatial domain, leaving the temporal...

We derive the Ensemble Average Propagator (EAP) for the case of straight axons (White Matter tissue elongation) and for undulated axons having different tortuosity rates (WM tissue compression). We show that under the hypothesis of having both the Magnitude and Phase of the dMRI signal we can quantify the asymmetry of the EAP which is related...

Many techniques have been proposed to divide the brain based on structural connectivity. However, even when produced by the same technique, the resulting parcellations tend to differ in the number, shape, and spatial localization of parcels across subject. Matching parcels across subjects is an open problem. We propose to use Optimal Transport...

Computational methods are crucial for the analysis of diffusion magnetic resonance imaging (MRI) of the brain. Computational diffusion MRI can provide rich information at many size scales, including local microstructure measures such as diffusion anisotropies or apparent axon diameters, whole‐brain connectivity information that describes the...

The recovery of microstructure-related features of the brain's white matter is a current challenge in diffusion MRI.To robustly estimate these important features from multi-shell diffusion MRI data, we propose to analytically regularize the coefficient estimation of the Mean Apparent Propagator (MAP)-MRI method using the norm of the Laplacian...