Short parietal lobe connections of the human and monkey brain

Marco Catani, Naianna Robertsson, Ahmad Beyh, Vincent Huynh, Francisco de Santiago Requejo, Henrietta Howells, Rachel L.C. Barrett, Marco Aiello, Carlo Cavaliere, Tim B. Dyrby, Kristine Krug, Maurice Ptito, Helen D'Arceuil, Stephanie J. Forkel, Flavio Dell'Acqua
Cortex. 2017-12-01; 97: 339-357
DOI: 10.1016/j.cortex.2017.10.022

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The parietal lobe has a unique place in the human brain. Anatomically, it is at
the crossroad between the frontal, occipital, and temporal lobes, thus providing
a middle ground for multimodal sensory integration. Functionally, it supports
higher cognitive functions that are characteristic of the human species, such as
mathematical cognition, semantic and pragmatic aspects of language, and abstract
thinking. Despite its importance, a comprehensive comparison of human and simian
intraparietal networks is missing. In this study, we used diffusion imaging
tractography to reconstruct the major intralobar parietal tracts in twenty-one
datasets acquired in vivo from healthy human subjects and eleven ex vivo datasets
from five vervet and six macaque monkeys. Three regions of interest (postcentral
gyrus, superior parietal lobule and inferior parietal lobule) were used to
identify the tracts. Surface projections were reconstructed for both species and
results compared to identify similarities or differences in tract anatomy (i.e.,
trajectories and cortical projections). In addition, post-mortem dissections were
performed in a human brain. The largest tract identified in both human and monkey
brains is a vertical pathway between the superior and inferior parietal lobules.
This tract can be divided into an anterior (supramarginal gyrus) and a posterior
(angular gyrus) component in both humans and monkey brains. The second prominent
intraparietal tract connects the postcentral gyrus to both supramarginal and
angular gyri of the inferior parietal lobule in humans but only to the
supramarginal gyrus in the monkey brain. The third tract connects the postcentral
gyrus to the anterior region of the superior parietal lobule and is more
prominent in monkeys compared to humans. Finally, short U-shaped fibres in the
medial and lateral aspects of the parietal lobe were identified in both species.
A tract connecting the medial parietal cortex to the lateral inferior parietal
cortex was observed in the monkey brain only. Our findings suggest a consistent
pattern of intralobar parietal connections between humans and monkeys with some
differences for those areas that have cytoarchitectonically distinct features in
humans. The overall pattern of intraparietal connectivity supports the special
role of the inferior parietal lobule in cognitive functions characteristic of

Copyright © 2017. Published by Elsevier Ltd.

DOI: 10.1016/j.cortex.2017.10.022
PMID: 29157936 [Indexed for MEDLINE]

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