Prolonged maturation of prefrontal white matter in chimpanzees

Delayed maturation in the prefrontal cortex, a brain region associated with complex cognitive processing, has been proposed to be specific to humans. However, we found, using a longitudinal design, that prefrontal white matter volume in chimpanzees increased gradually with age, and the increase appears to continue beyond the onset of puberty, as in humans. This provides the first evidence for a prolonged period of prefrontal connection elaboration in great apes

Using the Acropora digitifera genome to understand coral responses to environmental change

Despite the enormous ecological and economic importance of coral reefs, the keystone organisms in their establishment, the scleractinian corals, increasingly face a range of anthropogenic challenges including ocean acidification and seawater temperature rise1, 2, 3, 4. To understand better the molecular mechanisms underlying coral biology, here we decoded the approximately 420-megabase genome of Acropora digitifera using next-generation sequencing technology. This genome contains approximately 23,700 gene models. Molecular phylogenetics indicate that the coral and the sea anemone Nematostella vectensis diverged approximately 500 million years ago, considerably earlier than the time over which modern corals are represented in the fossil record (~240 million years ago)5. Despite the long evolutionary history of the endosymbiosis, no evidence was found for horizontal transfer of genes from symbiont to host. However, unlike several other corals, Acropora seems to lack an enzyme essential for cysteine biosynthesis, implying dependency of this coral on its symbionts for this amino acid. Corals inhabit environments where they are frequently exposed to high levels of solar radiation, and analysis of the Acropora genome data indicates that the coral host can independently carry out de novo synthesis of mycosporine-like amino acids, which are potent ultraviolet-protective compounds. In addition, the coral innate immunity repertoire is notably more complex than that of the sea anemone, indicating that some of these genes may have roles in symbiosis or coloniality. A number of genes with putative roles in calcification were identified, and several of these are restricted to corals. The coral genome provides a platform for understanding the molecular basis of symbiosis and responses to environmental changes

Developmental trajectory of the corpus callosum from infancy to the juvenile stage: Comparative MRI between chimpanzees and humans

[email protected] brains develop during early life is one of the most important topics in neuroscience because it underpins the neuronal functions that mature during this period. A comparison of the neurodevelopmental patterns among humans and nonhuman primates is essential to infer evolutional changes in neuroanatomy that account for higher-order brain functions, especially those specific to humans. The corpus callosum (CC) is the major white matter bundle that connects the cerebral hemispheres, and therefore, relates to a wide variety of neuronal functions. In humans, the CC area rapidly expands during infancy, followed by relatively slow changes. In chimpanzees, based on a cross-sectional study, slow changes in the CC area during the juvenile stage and later have also been reported. However, little is known about the developmental changes during infancy. A longitudinal study is also required to validate the previous cross-sectional observations about the chimpanzee CC. The present longitudinal study of magnetic resonance imaging scans demonstrates that the CC development in chimpanzees and humans is characterized by a rapid increase during infancy, followed by gradual increase during the juvenile stage. Several differences between the two species were also identified. First, there was a tendency toward a greater increase in the CC areas during infancy in humans. Second, there was a tendency toward a greater increase in the rostrum during the juvenile stage in chimpanzees. The rostral body is known to carry fibers between the bilateral prefrontal and premotor cortices, and is involved in behavior planning and control, verbal working memory, and number conception. The rostrum is known to carry fibers between the prefrontal cortices, and is involved in attention control. The interspecies differences in the developmental trajectories of the rostral body and the rostrum might be related to evolutional changes in the brain systems. © 2017 Sakai et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Stress rotations and the long-term weakness of the Median Tectonic Line and the Rokko-Awaji Segment

International audienceWe used a field analysis of rock deformation microstructures and mesostructures to reconstructthe long-term orientation of stresses around two major active fault systems in Japan, the Median TectonicLine and the Rokko-Awaji Segment. Our study reveals that the dextral slip of the two fault systems, activesince the Plio-Quaternary, was preceded by fault normal extension in the Miocene and sinistral wrenching inthe Paleogene. The two fault systems deviated the regional stress field at the kilometer scale in their vicinityduring each of the three tectonic regimes. The largest deviation, found in the Plio-Quaternary, is a more faultnormal rotation of the maximum horizontal stress to an angle of 79° with the fault strands, suggesting anextremely low shear stress on the Median Tectonic Line and the Rokko-Awaji Segment. Possible causes of thislong-term stress perturbation include a nearly total release of shear stress during earthquakes, a low staticfriction coefficient, or lowelastic properties of the fault zones comparedwith the country rock. Independently ofthe preferred interpretation, the nearly fault normal orientation of the direction of maximum compressionsuggests that the mechanical properties of the fault zones are inadequate for the buildup of a pore fluidpressure sufficiently elevated to activate slip. The long-term weakness of the Median Tectonic Line and theRokko-Awaji Segment may reside in low-friction/low-elasticity materials or dynamic weakening rather than inpreearthquake fluid overpressures