Diversity of cortico-descending projections: histological and diffusion MRI characterization in the monkey

Innocenti, Giorgio M.; Caminiti, Roberto; Rouiller, Eric M.; Knott, Graham; Dyrby, Tim B.; Descoteaux, Maxime; Thiran, Jean-Philippe

doi:10.1093/cercor/bhx363

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Journal article

Diversity of cortico-descending projections: histological and diffusion MRI characterization in the monkey

Innocenti, Giorgio M. Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden - Brain and Mind Institute, EPFL, Lausanne, Switzerland - EPFL-STI-IEL-LTS5, Station 11, Lausanne, Switzerland
Caminiti, Roberto Dipartimento di Fisiologia, SAPIENZA Universitá di Roma, Italy
Rouiller, Eric M. Department of Medicine, Swiss Primate Competence Center for Research, University of Fribourg, Switzerland
Knott, Graham BioEM Facility, Faculty of Life Sciences, EPFL, Lausanne, Switzerland
Dyrby, Tim B. Danish Research Centre for Magnetic Resonance, Copenhagen University Hospital, Denmark - Department of Applied Mathematics and Computer Science, Technical University of Denmark, Kongens Lyngby, Denmark
Descoteaux, Maxime Department of Computer Science, SCIL, Sherbrooke University, Québec, Canada
Thiran, Jean-Philippe EPFL-STI-IEL-LTS5, Station 11, Lausanne, Switzerland - Department of Radiology, CHUV, Lausanne, Switzerland

27.02.2018

Published in:

Cerebral Cortex. - 2019, vol. 29, no. 2, p. 788-801

English The axonal composition of cortical projections originating in premotor, supplementary motor (SMA), primary motor (a4), somatosensory and parietal areas and descending towards the brain stem and spinal cord was characterized in the monkey with histological tract tracing, electron microscopy (EM) and diffusion MRI (dMRI). These 3 approaches provided complementary information. Histology provided accurate assessment of axonal diameters and size of synaptic boutons. dMRI revealed the topography of the projections (tractography), notably in the internal capsule. From measurements of axon diameters axonal conduction velocities were computed. Each area communicates with different diameter axons and this generates a hierarchy of conduction delays in this order: a4 (the shortest), SMA, premotor (F7), parietal, somatosensory, premotor F4 (the longest). We provide new interpretations for i) the well-known different anatomical and electrophysiological estimates of conduction velocity; ii) why conduction delays are probably an essential component of the cortical motor command; and iii) how histological and dMRI tractography can be integrated.

Faculty

Faculté des sciences et de médecine

Department

Département de Médecine

Language