Hippocampal Pallium and Map-Like Memories through Vertebrate Evolution

The hippocampus in humans and other mammals is essential for episodic and relational memories. Comparative evidence indicates that a hippocampal pallium homologue is present in birds, reptiles, amphibians, ray-finned fishes, cartilaginous fishes and agnathans. Some of their characteristics, such as the topological position and the pattern of connectivity, appear remarkably well conserved. We review here substantial data showing that in all the vertebrate groups studied up to date, from fish to mammals, the hippocampus plays a fundamental role in spatial memory. In these vertebrates groups, the hippocampal pallium homologue is involved in the use of map-like, relational representations of the objective space that provide stable allocentric frames of reference, thus allowing flexible navigation. These similarities suggest a common evolutionary ancestry and indicate that the functional properties of the hippocampus appear early in the vertebrate phylogenesis and are retained through the independent evolution of the vertebrate lineages.

Putative adult neurogenesis in two domestic pigeon breeds(Columba livia domestica)：racing homer versus utility carneau pigeons

Generation of neurons in the brains of adult birds has been studied extensively in the telencephalon of song birds and few studies are reported on the distribution of PCNA and DCX in the telencephalon of adult non-song learning birds.We report here on adult neurogenesis throughout the brains of two breeds of adult domestic pigeons（Columba livia domestica）,the racing homer and utility carneau using endogenous immunohistochemical markers proliferating cell nuclear antigen（PCNA）for proliferating cells and doublecortin（DCX）for immature and migrating neurons.The distribution of PCNA and DCX immunoreactivity was very similar in both pigeon breeds with only a few minor differences.In both pigeons,PCNA and DCX immunoreactivity was observed in the olfactory bulbs,walls of the lateral ventricle,telencephalic subdivisions of the pallium and subpallium,diencephalon,mesencephalon and cerebellum.Generally,the olfactory bulbs and telencephalon had more PCNA and DCX cells than other regions.Two proliferative hotspots were evident in the dorsal and ventral poles of the lateral ventricles.PCNA-and DCX-immunoreactive cells migrated radially from the walls of the lateral ventricle into the parenchyma.In most telencephalic regions,the density of PCNA-and DCX-immunoreactive cells increased from rostral to caudal,except in the mesopallium where the density decreased from rostral to middle levels and then increased caudally.DCX immunoreactivity was more intense in fibres than in cell bodies and DCX-immunoreactive cells included small granular cells,fusiform bipolar cells,large round and or polygonal multipolar cells.The similarity in the distribution of proliferating cells and new neurons in the telencephalon of the two breeds of pigeons may suggest that adult neurogenesis is a conserved trait as an ecological adaptation irrespective of body size.

On Multi-Level Thinking and Scientific Understanding

Professor Duzheng YE＇s name has been familiar to me ever since my postdoctoral years at MIT with Professors Jule CHARNEY and Norman PHILLIPS, back in the late 1960 s. I had the enormous pleasure of meeting Professor YE personally in 1992 in Beijing. His concern to promote the very best science and to use it well, and his thinking on multi-level orderly human activities, reminds me not only of the communication skills we need as scientists but also of the multi-level nature of science itself. Here I want to say something（a） about what science is;（b） about why multi-level thinking—and taking more than one viewpoint—is so important for scientific as well as for other forms of understanding; and（c） about what is meant, at a deep level, by ＂scientific understanding＂ and trying to communicate it, not only with lay persons but also across professional disciplines. I hope that Professor YE would approve.

Brain differences in ecologically differentiatec sticklebacks

Populations that have recently diverged offer a powerful model for studying evolution. Ecological differences are expected to generate divergent selection on multiple traits, including neurobiological ones. Animals must detect, process, and act on information from their surroundings and the form of this information can be highly dependent on the environment. We might expect different environments to generate divergent selection not only on the sensory organs, but also on the brain regions responsible for processing sensory information. Here, we test this hypothesis using recently evolved reproductively isolated species pairs of threespine stickleback fish Gasterosteus aculeatus that have well-described differences in many morphological and behavioral traits corre- lating with ecological differences. We use a state-of-the-art method, magnetic resonance imaging, to get accurate volumetric data for 2 sensory processing regions, the olfactory bulbs and optic tecta. We found a tight correlation between ecology and the size of these brain regions relative to total brain size in 2 lakes with intact species pairs. Limnetic fish, which rely heavily on vision, had relatively larger optic tecta and smaller olfactory bulbs compared with benthic fish, which utilize olfaction to a greater extent. Benthic fish also had larger total brain volumes relative to their body size compared with limnetic fish. These differences were erased in a collapsed species pair in Enos Lake where anthropogenic disturbance has led to intense hybridization. Together these data indicate that evolution of sensory processing regions can occur rapidly and independently.

Integrative analyses of RNA editing,alternative splicing,and expression of young genes in human brain transcriptome by deep RNA sequencing

Next-generation RNA sequencing has been successfully used for identification of transcript assembly,evaluation of gene expression levels,and detection of post-transcriptional modifications.Despite these large-scale studies,additional comprehensive RNA-seq data from different subregions of the human brain are required to fully evaluate the evolutionary patterns experienced by the human brain transcriptome.Here,we provide a total of 6.5 billion RNA-seq reads fromdifferent subregions of the human brain.A significant correlation was observed between the levels of alternative splicing and RNA editing,which might be explained by a competition between the molecularmachineries responsible for the splicing and editing of RNA.Younghuman protein-coding genesdemonstrate biased expression to the neocortical and non-neocortical regions during evolution on the lineage leading to humans.Wealso found that a significantly greater number of young human protein-coding genes are expressed in the putamen,a tissue that was also observed to have the highest level of RNA-editing activity.The putamen,which previously received little attention,plays an important role in cognitive ability,and our data suggest a potential contribution of the putamen to human evolution.