Cerebral Sulci and Gyri Observed on Macaque Endocasts

Kobayashi, Yasushi; Matsui, Toshiyasu; Haizuka, Yoshinori; Ogihara, Naomichi; Hirai, Naoki; Matsumura, George

doi:10.1007/978-4-431-54553-8_14

Cited by 26 publications

(30 citation statements)

References 12 publications

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“…The utility of CT-based virtual endocasts for studies of primate brain evolution, including in examination of cortical-folding features, has been validated in both anthropology and paleoneurobiology (Zollikofer et al 1998;Bruner 2003Bruner , 2004Bruner , 2007Bruner , 2008Zollikofer and de León 2005;Carlson et al 2011;Balzeau et al 2012;Falk 2014;Kobayashi et al 2014). Our measurements taken on these CT scan-based virtual endocasts showed extremely high repeatability (average = 93%), implying reliable and consistent data collection.…”

Section: Endocast Validationmentioning

confidence: 81%

Cortical Folding of the Primate Brain: An Interdisciplinary Examination of the Genetic Architecture, Modularity, and Evolvability of a Significant Neurological Trait in Pedigreed Baboons (GenusPapio)

et al. 2015

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Folding of the primate brain cortex allows for improved neural processing power by increasing cortical surface area for the allocation of neurons. The arrangement of folds (sulci) and ridges (gyri) across the cerebral cortex is thought to reflect the underlying neural network. Gyrification, an adaptive trait with a unique evolutionary history, is affected by genetic factors different from those affecting brain volume. Using a large pedigreed population of 1000 Papio baboons, we address critical questions about the genetic architecture of primate brain folding, the interplay between genetics, brain anatomy, development, patterns of cortical-cortical connectivity, and gyrification's potential for future evolution. Through Mantel testing and cluster analyses, we find that the baboon cortex is quite evolvable, with high integration between the genotype and phenotype. We further find significantly similar partitioning of variation between cortical development, anatomy, and connectivity, supporting the predictions of tension-based models for sulcal development. We identify a significant, moderate degree of genetic control over variation in sulcal length, with gyrus-shape features being more susceptible to environmental effects. Finally, through QTL mapping, we identify novel chromosomal regions affecting variation in brain folding. The most significant QTL contain compelling candidate genes, including gene clusters associated with Williams and Down syndromes. The QTL distribution suggests a complex genetic architecture for gyrification with both polygeny and pleiotropy. Our results provide a solid preliminary characterization of the genetic basis of primate brain folding, a unique and biomedically relevant phenotype with significant implications in primate brain evolution.KEYWORDS gyrification; QTL; cerebral cortex; heritability; primate brain; evolution; modularity; Papio hamadryas T HE extent of folding of the cerebral cortex, known as "cortical gyrification," has dramatically increased during primate evolution, in parallel with increasing brain volumes. The cortex of Old World monkeys is significantly more folded (gyrified) than that of New World monkeys (Zilles et al. 1989;Martin 1990), and the great apes have the highest degree of gyrification in nonhuman primates (Preuss et al. 2004). Humans are outliers even within the primate clade, with our brain being almost 30% more folded than that of chimps (Rogers et al. 2010). Powerful physical constraints on the upper limit of human neonatal brain volume drive selection toward the most compact brain possible (Rosenberg and Trevathan 2002), while humankind's ecological niche demands high cognitive potential. Since the cell bodies of neurons-the functional units of information processing in the brain-are located in the outermost layer of the laminar brain system, folding the cerebral cortex is an effective method of increasing surface area in which to allocate neurons with minimal overall brain volume expansion. Selection for a larger brain volume does not autom...

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Section: Endocast Validationmentioning

confidence: 81%

Cortical Folding of the Primate Brain: An Interdisciplinary Examination of the Genetic Architecture, Modularity, and Evolvability of a Significant Neurological Trait in Pedigreed Baboons (GenusPapio)

et al. 2015

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“…The boundaries of the parietal bone and parietal lobe do not show a fixed spatial relationship, but their respective dimensions are nonetheless correlated (Bruner et al 2015a), and there is a geometrical correspondence of their respective surfaces (Moss and Young 1960; Kobayashi et al 2014). The globularity of the modern human braincase is primarily determined by the size and shape of the parietal bone, which has a species-specific morphology in Homo sapiens.…”

Section: Discussionmentioning

confidence: 99%

Evidence for expansion of the precuneus in human evolution

et al. 2016

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The evolution of neurocranial morphology in Homo sapiens is characterized by bulging of the parietal region, a feature unique to our species. In modern humans, expansion of the parietal surface occurs during the first year of life, in a morphogenetic stage which is absent in chimpanzees and Neandertals. A similar variation in brain shape among living adult humans is associated with expansion of the precuneus. Using MRI-derived structural brain templates, we compare medial brain morphology between humans and chimpanzees through shape analysis and geometrical modeling. We find that the main spatial difference is a prominent expansion of the precuneus in our species, providing further evidence of evolutionary changes associated with this area. The precuneus is a major hub of brain organization, a central node of the default-mode network, and plays an essential role in visuospatial integration. Together, the comparative neuroanatomical and paleontological evidence suggest that precuneus expansion is a specialization of Homo sapiens that evolved in the last 150,000 years that may be associated with recent human cognitive specializations.

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“…Of course, much information is lost from a real brain to its endocranial cast, which is a sort of geometrical model able to supply only some scattered information on cerebral gross cortical features and general proportions. Furthermore, the meninges and the cerebrospinal fluid are interposed between the cerebral cortex and the internal table of the braincase, separating their respective surfaces and smoothing the endocranial imprints, most of all in larger skulls [Kobayashi et al, 2014;Van Minh and Hamada, 2017]. Yet, despite these limitations, this is the only direct information we can have on the brains of extinct taxa and, therefore, deserves attention.…”

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confidence: 98%

Human Paleoneurology and the Evolution of the Parietal Cortex

Bruner¹

2018

Brain Behav Evol

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Paleoneurology deals with the study of brain anatomy in fossil species, as inferred from the morphology of their endocranial features. When compared with other living and extinct hominids, Homo sapiens is characterized by larger parietal bones and, according to the paleoneurological evidence, also by larger parietal lobes. The dorsal elements of the posterior parietal cortex (superior parietal lobules, precuneus, and intraparietal sulcus) may be involved in these morphological changes. This parietal expansion was also associated with an increase in the corresponding vascular networks, and possibly with increased heat loads. Only H. sapiens has a specific early ontogenetic stage in which brain form achieves such globular appearance. In adult modern humans, the precuneus displays remarkable variation, being largely responsible for the longitudinal parietal size. The precuneus is also much more expanded in modern humans than in chimpanzees. Parietal expansion is not influenced by brain size in fossil hominids or living primates. Therefore, our larger parietal cortex must be interpreted as a derived feature. Spatial models suggest that the dorsal and anterior areas of the precuneus might be involved in these derived morphological variations. These areas are crucial for visuospatial integration, and are sensitive to both genetic and environmental influences. This article reviews almost 20 years of my collaborations on human parietal lobe evolution, integrating functional craniology, paleoneurology, and evolutionary neuroanatomy.

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Cerebral Sulci and Gyri Observed on Macaque Endocasts

Cited by 26 publications

References 12 publications

Cortical Folding of the Primate Brain: An Interdisciplinary Examination of the Genetic Architecture, Modularity, and Evolvability of a Significant Neurological Trait in Pedigreed Baboons (GenusPapio)

Cortical Folding of the Primate Brain: An Interdisciplinary Examination of the Genetic Architecture, Modularity, and Evolvability of a Significant Neurological Trait in Pedigreed Baboons (GenusPapio)

Evidence for expansion of the precuneus in human evolution

Human Paleoneurology and the Evolution of the Parietal Cortex

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