The heterogeneous composition of tissue-resident and invading immune cells within the TME alone permitted a clear distinction between gliomas and brain metastases (BrM). Here, we have mapped the leukocyte landscape of brain tumors using high-dimensional single-cell profiling (CyTOF). Whether the TME is predominantly shaped by the CNS micromilieu or by the malignancy itself is unknown, as is the diversity, origin, and function of CNS tumor-associated macrophages (TAMs). A highly immunosuppressive tumor microenvironment (TME) influences brain tumor outgrowth. Electronic address: malignancies can either originate from within the CNS (gliomas) or invade from other locations in the body (metastases). 6 Institute of Experimental Immunology, University of Zurich, Zurich 8057, Switzerland.5 Laboratory of Molecular Neuro-Oncology, Department of Neurology, Clinical Neuroscience Center, University Hospital Zurich and University of Zurich, Zurich 8091, Switzerland Department of Neurosurgery, Clinical Neuroscience Center, University Hospital Zurich and University of Zurich, Zurich 8091, Switzerland.4 Department of Neurosurgery, Clinical Neuroscience Center, University Hospital Zurich and University of Zurich, Zurich 8091, Switzerland.3 Department of Neuropathology, University Hospital Zurich and University of Zurich, Zurich 8091, Switzerland.2 Laboratory of Molecular Neuro-Oncology, Department of Neurology, Clinical Neuroscience Center, University Hospital Zurich and University of Zurich, Zurich 8091, Switzerland.1 Institute of Experimental Immunology, University of Zurich, Zurich 8057, Switzerland.By replicating the major features of these tracts identified by histological techniques in monkey, we show that DSI has the potential to cast new light on the organization of the human brain in the normal state and in clinical disorders. These findings using DSI and validated with reference to autoradiographic tract tracing in the monkey represent a considerable advance in the understanding of the fibre pathways in the cerebral white matter. We suggest new interpretations of the putative functions of these fibre bundles based on the cortical areas that they link. We identified 10 long association fibre bundles with DSI that match the observations in the isotope material: emanating from the parietal lobe, the superior longitudinal fasciculus subcomponents I, II and III from the occipital-parietal region, the fronto-occipital fasciculus from the temporal lobe, the middle longitudinal fasciculus and from rostral to caudal, the uncinate fasciculus, extreme capsule and arcuate fasciculus from the occipital-temporal region, the inferior longitudinal fasciculus and from the cingulate gyrus, the cingulum bundle. We then compared the results with available expositions of white matter pathways in the monkey using autoradiographic histological tract tracing. We therefore used diffusion spectrum imaging (DSI) that has the ability to resolve crossing fibres at the scale of single MRI voxels, and identified the long association tracts in the monkey brain.

Diffusion tensor imaging (DTI) is able to demonstrate fibre tracts non-invasively, but present approaches have been hampered by the inability to visualize fibres that have intersecting trajectories (crossing fibres), and by the lack of a detailed map of the origins, course and terminations of the white matter pathways. National Association for Research on Schizophrenia & Affective DisordersДЄssociation fibre pathways of the brain: parallel observations from diffusion spectrum imaging and autoradiographyUnderstanding the long association pathways that convey cortical connections is a critical step in exploring the anatomic substrates of cognition in health and disease.

Human brain mapping supplement