Research Group "Anatomical Analysis of the Organization of the Human and Non-Human Primate Brain"

We study the cortical microanatomy with high-field (7 Tesla) magnetic resonance imaging (MRI) with a structural resolution in the sub-millimeter range. In order to unravel the structural basis for the high-field MRI contrast, we cross-validate the findings with "classical" anatomical techniques. To achieve this, we scan human postmortem brains or the brains of laboratory animals with MRI. After scanning, the brains are fixed, embedded in paraffin, and sectioned with a conventional microtome or they are cryoprotected, frozen, and sectioned with a cryostat. We then study various microstructural aspects, e.g., cytoarchitecture with the "classical" Nissl stain or myeloarchitecture with myelin stains. Since high-field MRI scans have been obtained from the same brains beforehand, we can directly correlate and cross-validate the two different approaches.

Not only cytoarchitecture or myeloarchitecture but also connectivity profiles structurally and functionally characterize cortical areas. Diffusion-weighted magnetic resonance imaging (DWI) and probabilistic tractography non-invasively measure such connectivity profiles in living subjects. We combine DWI with an automatic clustering algorithm in order to identify cortical regions with internally coherent but mutually distinct connectivity. This noninvasive approach supplements the "classical" invasive techniques of structurally mapping the cerebral cortex (e.g., cytoarchitecture or myeloarchitecture) and sheds new light on the problem of structure-function relationships in the human cortex.

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