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
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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.
Faculté des sciences et de médecine
Département de Médecine
  • English
Biological sciences
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