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Conservation of brain connectivity and wiring across the mammalian class


Over 100 years ago, Ramon y Cajal hypothesized that two forces played a role in the evolution of mammalian brain connectivity: minimizing wiring costs and maximizing conductivity speed. Using diffusion MRI, we reconstructed the brain connectomes of 123 mammalian species. Network analysis revealed that both connectivity and the wiring cost are conserved across mammals. We describe a conservation principle that maintains the overall connectivity: species with fewer interhemispheric connections exhibit better intrahemispheric connectivity.

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Fig. 1: Global mammalian conservation of connectivity and wiring.
Fig. 2: Intraspecific connectivity conservation.
Fig. 3: Strong connections drive hemispheric connectivity.

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Data availability

The data that support the findings of this study are available from the corresponding author upon request.

Code availability

All codes used in this study are part of Matlab’s (Mathworks) statistics and data analysis toolbox codes. The circular graphs were generated using P. Kassebaum’s (2020) circularGraph (


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We thank K. Or, R. Elazari, S. Landau, A. Scheinin, D. Morik, N. Avni-Magen, N. Kornfeld-Schor, I. Horowitz and A. Kafri for help with brain collection. We also thank A. Leemans for help with the fiber-tracking procedures. Y.A. thanks the Strauss Center for Computational Neuroimaging for help in data acqusition.

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Authors and Affiliations



Y.A. was responsible for data acquisition and data analysis. O.Z. was responsible for code and software development. A.M. and A.B. were in charge of sample collection and preparation. Y.Y. was responsible for study and analysis design and wrote the paper, together with Y.A. All authors contributed to the discussion and interpretation of the results.

Corresponding authors

Correspondence to Yaniv Assaf or Yossi Yovel.

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Competing interests

The authors declare no competing interests.

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Peer review information Nature Neuroscience thanks Daniel Alexander, Rogier Mars and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Brain Regions.

Illustration of the different brain regions that correspond to the circular graphs shown in Fig. 1 matched by color and shading.

Extended Data Fig. 2 Strong Connections.

A heat-map showing all strong connections projected on-to a mid-sagittal slice.

Supplementary information

Supplementary Information

Supplementary Figs. 1–17 and Supplementary Table 1.

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Assaf, Y., Bouznach, A., Zomet, O. et al. Conservation of brain connectivity and wiring across the mammalian class. Nat Neurosci 23, 805–808 (2020).

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