Comparing Brain Structure Connections in Humans and Chimps

Greg Howard
18th July, 2024

Comparing Brain Structure Connections in Humans and Chimps

Image Source: Natural Science News, 2024

Key Findings

  • The study by Paris-Saclay University examined superficial white matter bundles (SWMBs) in human and chimpanzee brains
  • Researchers found various SWMB shapes, including U-shaped, 6-shaped, and J-shaped fibers, using diffusion MRI tractography
  • Differences in SWMB localization between humans and chimpanzees suggest variations in brain folding processes, linked to cognitive functions
Diffusion MRI tractography (dMRI) has revolutionized our understanding of white matter pathways in the human brain. While extensive research has been conducted on long-range connections, superficial white matter bundles (SWMBs) remain relatively underexplored. A recent study by Paris-Saclay University aims to bridge this gap by examining SWMB connectivity in both human and chimpanzee brains using innovative empirical and geometric methodologies[1]. This study leverages two anatomical atlases—the Ginkgo Chauvel chimpanzee atlas and the Ginkgo Chauvel human atlas—to classify SWMB morphology objectively, providing new insights into the superficial connectivity of the chimpanzee brain and the variability in these bundles' shapes. The study's primary objective is to explore the similarities and differences in SWMBs between humans and chimpanzees, shedding light on the evolution and organization of these crucial neural structures. Previous research has shown that humans exhibit significant age-related brain volumetric decline in regions such as the hippocampus and the frontal lobe, unlike chimpanzees, who experience minimal changes in cortical organization and sulcus folding over their lifespan[2]. This new study aims to further understand these differences by focusing on the less-studied SWMBs. Using diffusion MRI tractography, researchers identified various SWMB morphologies, including well-known U-shaped fibers and more complex geometries like 6 and J shapes. These findings are significant because they provide a more nuanced understanding of brain connectivity beyond the long-range connections that have been the focus of most previous studies. For instance, earlier research has highlighted the importance of short intralobar frontal connections in humans, which are crucial for motor learning, verbal fluency, and working memory[3]. This study extends that understanding to SWMBs, offering a broader perspective on brain connectivity. The researchers employed an isomap-based shape analysis approach to analyze the localization of different bundle morphologies, which are believed to reflect the brain's gyrification process. Gyrification refers to the folding of the cerebral cortex, which increases the brain's surface area and is associated with higher cognitive functions. The study found that the localization of these bundle morphologies differed between humans and chimpanzees, suggesting variations in the gyrification process between the two species. This aligns with previous findings that the human brain has unique anatomical specializations, particularly in the white matter organization[4]. The study's use of sparse representations of SWMB morphology is particularly noteworthy. Sparse representations allow for a more efficient and accurate classification of complex shapes, making it easier to identify subtle differences between species. This methodological innovation could pave the way for future research into other underexplored aspects of brain connectivity. In summary, this study by Paris-Saclay University provides a comprehensive examination of SWMB connectivity in human and chimpanzee brains, offering new insights into the evolution and organization of these neural structures. By identifying both commonalities and disparities in SWMBs, the research contributes to a deeper understanding of brain connectivity and its implications for cognitive functions. This work builds on previous findings about brain volumetric decline and white matter organization, offering a more complete picture of the intricate network of connections that underpin higher cognitive functions in humans and their closest living relatives.

GeneticsBiochemAnimal Science

References

Main Study

1) Comparative analysis of the chimpanzee and human brain superficial structural connectivities.

Published 17th July, 2024

https://doi.org/10.1007/s00429-024-02823-2

Related Studies

2) Age-related effects in the neocortical organization of chimpanzees: gray and white matter volume, cortical thickness, and gyrification.

https://doi.org/10.1016/j.neuroimage.2014.06.053

3) Short frontal lobe connections of the human brain.

https://doi.org/10.1016/j.cortex.2011.12.001

4) A comprehensive atlas of white matter tracts in the chimpanzee.

https://doi.org/10.1371/journal.pbio.3000971


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