Numerical Analysis of the Cerebral Cortex in Diprotodontids (Marsupialia; Australidelphia) and Comparison with Eutherian Brains

Jyothilakshmi, T.K.; Gurovich, Yamila; Ashwell, Ken W.S.

doi:10.1016/j.zool.2020.125845

Cited by 9 publications

(13 citation statements)

References 65 publications

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“…We computed the log‐shape ratios of neocortex volumes from Pirlot (1981) for 17 species of marsupials, including members of Didelphimorphia, Dasyuromorphia, Peramelemorphia, and Diprotodontia; and isocortex gray matter volumes for 19 Diprotodontian species from Jyothilakshmi et al. (2020). These log‐shape ratios were based on the larger datasets of histology‐based brain region volumes of which the neo/isocortical volume data were part (for computation of these from the full datasets, refer to the code on github).…”

Section: Methodsmentioning

confidence: 99%

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Global elongation and high shape flexibility as an evolutionary hypothesis of accommodating mammalian brains into skulls

et al. 2021

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Little is known about how the large brains of mammals are accommodated into the dazzling diversity of their skulls. It has been suggested that brain shape is influenced by relative brain size, that it evolves or develops according to extrinsic or intrinsic mechanical constraints, and that its shape can provide insights into its proportions and function. Here, we characterize the shape variation among 84 marsupial cranial endocasts of 57 species including fossils, using three-dimensional geometric morphometrics and virtual dissections. Statistical shape analysis revealed four main patterns: over half of endocast shape variation ranges from elongate and straight to globular and inclined; little allometric variation with respect to centroid size, and none for relative volume; no association between locomotion and endocast shape; limited association between endocast shape and previously published histological cortex volumes. Fossil species tend to have smaller cerebral hemispheres. We find divergent endocast shapes in closely related species and within species, and diverse morphologies superimposed over the main variation. An evolutionarily and individually malleable brain with a fundamental tendency to arrange into a spectrum of elongate-to-globular shapes-possibly mostly independent of brain function-may explain the accommodation of brains within the enormous diversity of mammalian skull form.

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Section: Methodsmentioning

confidence: 99%

“…In one case for Pirlot (1981) and five cases for Jyothilakshmi et al. (2020), a species in our dataset was matched with a value from a congeneric species of a similar body weight (noted in Table S1).…”

Section: Methodsmentioning

confidence: 99%

Global elongation and high shape flexibility as an evolutionary hypothesis of accommodating mammalian brains into skulls

et al. 2021

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“…A number of methodological factors need to be taken into account when interpreting our findings. The scaling relationships found are fitted on a representative sample across a range of monkeys and apes but do not necessarily generalize to all species (Jyothilakshmi et al 2020); positive allometry between white and gray matter scaling is a conserved feature in primates, but absent in artiodactyls (hoofed animals including giraffes and deer) (Mota et al 2019). A second point to consider is that our current analyses are limited to the cerebrum and corticocortical connections.…”

Section: Discussionmentioning

confidence: 99%

Scaling principles of white matter brain connectivity

Ardesch

Scholtens

et al. 2021

Preprint

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Brains come in many shapes and sizes. Nature has endowed big-brained primate species like humans with a proportionally large cerebral cortex. White matter connectivity - the brain's infrastructure for long-range communication - might not always scale at the same pace as the cortex. We investigated the consequences of this allometric scaling for white matter brain network connectivity. Structural T1 and diffusion MRI data were collated across fourteen primate species, describing a comprehensive 350-fold range in brain volume. We report volumetric scaling relationships that point towards a restriction in macroscale connectivity in larger brains. Building on previous findings, we show cortical surface to outpace white matter volume and the corpus callosum, suggesting the emergence of a white matter 'bottleneck' of lower levels of connectedness through the corpus callosum in larger brains. At the network level, we find a potential consequence of this bottleneck in shaping connectivity patterns, with homologous regions in the left and right hemisphere showing more divergent connectivity in larger brains. Our findings show conserved scaling relationships of major brain components and their consequence for macroscale brain circuitry, providing a comparative framework for expected connectivity architecture in larger brains such as the human brain.

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“…While a confident dissection of the neocortical portion of the cerebral hemispheres was not possible, we matched data from two publications with a sample that was overlapping ours. We computed the log-shape ratios of neocortex volumes from Pirlot (1981) for 17 species of marsupials, including members of Didelphimorphia, Dasyuromorphia, Peramelemorphia and Diprotodontia; and isocortex grey matter volumes for 19 Diprotodontian species from Jyothilakshmi et al (2020). These log-shape ratios were based on the larger datasets of histology-based brain region volumes of which the neo/isocortical volume data were part (for computation of these from the full datasets, refer to the relevant file on github).…”

Section: Methodsmentioning

confidence: 99%

“…These log-shape ratios were based on the larger datasets of histology-based brain region volumes of which the neo/isocortical volume data were part (for computation of these from the full datasets, refer to the relevant file on github). In one case for Pirlot (1981) and five cases for Jyothilakshmi et al (2020), a species in our dataset was matched with a value from a congeneric species of a similar body weight (noted in Supplementary Table 1).…”

Section: Methodsmentioning

confidence: 99%

Global elongation and high shape flexibility as an evolutionary hypothesis of accommodating mammalian brains into skulls

Weisbecker

Rowe

Wroe

et al. 2020

Preprint

View full text Add to dashboard Cite

Little is known about how the large brains of mammals are accommodated into the dazzling diversity of their skulls. It has been suggested that brain shape is influenced by relative brain size, that it evolves or develops according to extrinsic or intrinsic mechanical constraints, and that its shape can provide insights into its proportions and function. Here, we characterise the shape variation among 84 marsupial cranial endocasts of 57 species including fossils, using 3D geometric morphometrics and virtual dissections. Statistical shape analysis revealed four main patterns: over half of endocast shape variation ranges between elongate and straight to globular and inclined; little allometric variation with respect to centroid size, and none for relative volume; no association between locomotion and endocast shape; limited association between endocast shape and previously published histological cortex volumes. Fossil species tend to have smaller cerebral hemispheres. We find divergent endocast shapes in closely related species and within species, and diverse morphologies superimposed over the main variation. An evolutionarily and individually malleable brain with a fundamental tendency to arrange into a spectrum of elongate-to-globular shapes – possibly mostly independent of brain function - may explain the accommodation of brains within the enormous diversity of mammalian skull form.

show abstract

Numerical Analysis of the Cerebral Cortex in Diprotodontids (Marsupialia; Australidelphia) and Comparison with Eutherian Brains

Cited by 9 publications

References 65 publications

Global elongation and high shape flexibility as an evolutionary hypothesis of accommodating mammalian brains into skulls

Global elongation and high shape flexibility as an evolutionary hypothesis of accommodating mammalian brains into skulls

Scaling principles of white matter brain connectivity

Global elongation and high shape flexibility as an evolutionary hypothesis of accommodating mammalian brains into skulls

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