Posts Tagged 'magnetic resonance'

Human brain variation

One year ago Croxson and colleagues published a survey on human and macaques brain variation, a paper which has been issued this month in Cerebral Cortex. They considered variation in white and grey matter, comparing inter and intra-specific patterns, and discussing similarities between the evolutionary and individual degree of variability. This study evidences the importance of variation as a source of evolutionary possibilities and constraints. The survey was based on only 10-20 individuals and, despite any statistical reassurance, we have to recognize that this is an unusual sample size for a study targeted to describe and quantify intra-specific diversity. Furthermore, in these kinds of analyses one has constantly the sensation that phylogenetic differences (macaque-human) are still interpreted as evolutionary differences (ancestral-descendant), which is definitely an inappropriate perspective when dealing with extant species. Also, the fact that we keep on using the term “monkey” when referring to one single species of hundreds of living, independent and diverse ones, denotes a still-alive linear approach to the evolutionary schemes (the old fashion progression monkey -> ape -> human). This paper was then commented by Aida Gómez-Robles, who discussed the pros and cons of this study. Some months later, Reardon and colleagues published a similar analysis, but on a huge sample. In her review, Aida Gómez-Robles pointed to endocasts as a potential source of additional information on intra-specific brain variation. Definitely a good point, and a valiant position to be presented in a mainstream journal on cognition. Endocasts and macroanatomy are issues which are often neglected in neuroscience. Nonetheless, two aspects must be taken into account. First, macroanatomy and morphology still hide many issues which suffer a dramatic lack of information, and that can reveal unexpected suprises. This is also true taking into account traditional neuroanatomy and, for example, in our last survey on human brain variation (on 265 individuals) the precuneus still stands as a major source of gross morphological human diversity. Second, although endocasts can’t provide a comprehensive information on brain biology, they can remarkably help to increase the sample size when dealing with primates and especially hominoids, because of the many collections available as dry or digital skulls. A recent study on the degree of endocranial metric variation in apes, humans, and hominids can be found here.

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  • Primate brain folding
    A recent work, analyzing the development and evolution of the primate cortical folding, evidences two separate folding processes of the neocortex. Namba and colleagues examine two subtypes of neocortex, the dorsal isocortex, defined as the portion of neocortex limited laterally by the lateral fissure (LF) and medially by the cingulate sulcus (CiS), and the p […]

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  • Seven Million Years of Human Evolution
    This fascinating visual presentation from the American Museum of Natural History outlines what we know about human evolution by combining …Continue reading →

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  • Researchers develop non-invasive deep brain stimulation method
    Researchers at MIT have developed a new method of electrically stimulating deep brain tissues without opening the skullSince 1997, more than 100,000 Parkinson’s Disease patients have been treated with deep brain stimulation (DBS), a surgical technique that involves the implantation of ultra-thin wire electrodes. The implanted device, sometimes referred to as […]

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