Journal article
Diversity of Cortico-descending Projections: Histological and Diffusion MRI Characterization in the Monkey
Karolinska Institutet1
University of Rome La Sapienza2
University of Fribourg3
Swiss Federal Institute of Technology Lausanne4
Visual Computing, Department of Applied Mathematics and Computer Science, Technical University of Denmark5
Department of Applied Mathematics and Computer Science, Technical University of Denmark6
Université de Sherbrooke7
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.
Language: | English |
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Publisher: | Oxford University Press |
Year: | 2019 |
Pages: | 788-801 |
ISSN: | 14602199 and 10473211 |
Types: | Journal article |
DOI: | 10.1093/cercor/bhx363 |
ORCIDs: | Dyrby, Tim B. |