These studies left no doubt that the human cerebral cortex has ex

These studies left no doubt that the human cerebral cortex has expanded significantly relative to other hominids, including introduction

of new regions in the frontal and parietotemporal lobes Galunisertib concentration in humans (Dunbar, 1993, Fjell et al., 2013, Preuss, 1995, Rakic, 2009 and Teffer and Semendeferi, 2012). It also became evident that although the basic principles of brain development in all mammals may be conserved, the modifications of developmental events during evolution produce not only quantitative but qualitative changes as well (Table 1). Due to the limits of the space, we cannot provide a comprehensive review of this wide-ranging topic. Instead, we will focus on the expansion and elaboration of the human cerebral neocortex and provide our own personal perspective on some of the key advances in this area, including the high promise, as well as enormous challenges ahead. We organize our thoughts into two major areas—the phenotype-driven and genome-driven approaches,

which, unfortunately, only rarely meet in the middle. Our hope is that in the near future, it will be possible to connect some of the known human genetic adaptations to the developmental and maturational features that GSK J4 datasheet underlie uniquely human cognitive abilities. It is well established that the expansion of the cortex occurs primarily in surface area rather than in thickness. This is most pronounced in anthropoid primates, including humans, in which the neocortex comprises up to 80% of the brain mass. We have also known for a long time that the neocortex is subdivided into distinct cytoarchitectonic areas with neurons organized in horizontal layers or laminae, and vertical (radial) columns through or modules, which have increased in

number, size, and complexity during cortical evolution (Mountcastle, 1995 and Goldman-Rakic, 1987). Of course, brain size is not simply a matter of cell number; it also reflects cell density arrangements and connectivity (Herculano-Houzel et al., 2008), which is relevant here, as the distance between cell bodies in the cerebral cortex, especially prefrontal regions of humans, is greater than in other primates (Semendeferi et al., 2011). Thus, three essential features account for the changes in cerebral size over mammalian evolution: large changes in cell number, morphology, and composition. However, it is not sufficient to enlarge the entire brain, as Neanderthals had large brains, and modern human brain size may differ by 2-fold among individuals. From this perspective, many genes that modify cell cycle can increase or decrease brain size but not necessarily in a manner that is relevant to cerebral evolution. A salient recent example worth discussing is the sophisticated analysis of the function of BAF-170 in mouse brain development (Tuoc et al., 2013).

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