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Brain Struct Funct. 2016 Nov;221(8):4059-4071. Epub 2015 Dec 1.

The extreme capsule fiber complex in humans and macaque monkeys: a comparative diffusion MRI tractography study.

Author information

1
Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK. rogier.mars@psy.ox.ac.uk.
2
Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, 6525 EZ, Nijmegen, The Netherlands. rogier.mars@psy.ox.ac.uk.
3
Oxford Centre for Functional MRI of the Brain, Nuffield Department of Clinical Neurosciences, John Radcliffe Hospital, University of Oxford, Oxford, OX3 9DU, UK.
4
Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford, OX1 3UD, UK.
5
Oxford Centre for Human Brain Activity, Department of Psychiatry, Warneford Hospital, University of Oxford, Oxford, OX3 7JX, UK.
6
Icahn School of Medicine at Mount Sinai, New York, NY, 10029-6574, USA.
7
Cancer Research UK/Medical Research Council Oxford Institute for Radiation Oncology, Department of Oncology, University of Oxford, Oxford, OX3 7DQ, UK.

Abstract

We compared the course and cortical projections of white matter fibers passing through the extreme capsule in humans and macaques. Previous comparisons of this tract have suggested a uniquely human posterior projection, but these studies have always employed different techniques in the different species. Here we used the same technique, diffusion MRI, in both species to avoid attributing differences in techniques to differences in species. Diffusion MRI-based probabilistic tractography was performed from a seed area in the extreme capsule in both human and macaques. We compared in vivo data of humans and macaques as well as one high-resolution ex vivo macaque dataset. Tractography in the macaque was able to replicate most results known from macaque tracer studies, including selective innervation of frontal cortical areas and targets in the superior temporal cortex. In addition, however, we also observed some tracts that are not commonly reported in macaque tracer studies and that are more reminiscent of results previously only reported in the human. In humans, we show that the ventrolateral prefrontal cortex innervations are broadly similar to those in the macaque. These results suggest that evolutionary changes in the human extreme capsule fiber complex are likely more gradual than punctuated. Further, they demonstrate both the potential and limitations of diffusion MRI tractography.

KEYWORDS:

Comparative neuroscience; Surface projection; Temporal cortex; Tractography; Ventrolateral prefrontal cortex

PMID:
26627483
PMCID:
PMC5065901
DOI:
10.1007/s00429-015-1146-0
[Indexed for MEDLINE]
Free PMC Article

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