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Neuroimage. 2019 Oct 1;199:418-426. doi: 10.1016/j.neuroimage.2019.06.019. Epub 2019 Jun 8.

Tractography-based parcellation does not provide strong evidence of anatomical organisation within the thalamus.

Author information

1
Developmental Imaging and Biophysics Section, UCL Great Ormond Street Institute of Child Health, University College London, London, United Kingdom. Electronic address: j.clayden@ucl.ac.uk.
2
Neuroradiological Academic Unit, UCL Institute of Neurology, University College London, London, United Kingdom; Leonard Wolfson Experimental Neurology Centre, UCL Institute of Neurology, Queen Square, London, United Kingdom. Electronic address: d.thomas@ucl.ac.uk.
3
Department of Clinical and Movement Neurosciences, UCL Institute of Neurology, University College London, London, United Kingdom. Electronic address: a.kraskov@ucl.ac.uk.

Abstract

Connectivity-based parcellation of subcortical structures using diffusion tractography is now a common paradigm in neuroscience. These analyses often imply voxel-level specificity of connectivity, and the formation of compact, spatially coherent clusters is often taken as strong imaging-based evidence for anatomically distinct subnuclei in an individual. In this study, we demonstrate that internal structure in diffusion anisotropy is not necessary for a plausible parcellation to be obtained, by spatially permuting diffusion parameters within the thalami and repeating the parcellation. Moreover, we show that, in a winner-takes-all paradigm, most voxels receive the same label before and after this shuffling process-a finding that is stable across image acquisitions and tractography algorithms. We therefore suggest that such parcellations should be interpreted with caution.

KEYWORDS:

Connectivity; Diffusion; Magnetic resonance imaging; Parcellation; Tractography

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