There is an interesting analysis by Madeleine Chollet and colleagues on brain landmarking. They analyzed and quantified intra- and inter-observer error when collecting coordinates from 3D digital brains. Results are encouraging, evidencing average errors of 1.9 and 1.1 mm, respectively. However, values are much variable, depending upon the specific brain area. Generally, midsagittal landmarks show less uncertainty than parasagittal ones, and subcortical landmarks are more reliable than cortical ones (good for me: that’s why most of my papers are on midsagittal and subcortical morphology!). The analysis has been performed only on 10 specimens, and larger samples can surely add to the current results. Furthermore, in this study only the left hemisphere has been considered, in which sulci and gyri are generally easier to recognize. Despite these limits, the paper supplies clear results and useful comments. These kinds of analyses are necessary to promote quantitative perspectives in landmark-based morphometrics. For an excellent example of quantitative approach in paleoneurology I recommend to see the article by Simon Neubauer and colleagues on australopiths’ brain size estimations.
Posts Tagged 'geometric morphometrics'
Tags: Brain shape, geometric morphometrics, Landmarking
Tags: chimpanzee, geometric morphometrics, hemispheric asymmetries, human brain
Cerebral asymmetries are a thorny issue in both paleoneurology and human neuroanatomy: despite their relevance, their origin and actual variations are elusive. Conceptual and technical problems tend to hamper conclusive statements, as evidenced by the many disagreements and uncertainties in the field. A recent paper on asymmetries in human and chimpanzee brains has added a geometric perspective to the topic. This shape analysis suggests that humans and chimpanzees have the same kind of asymmetries, with humans showing a larger degree of variation and expression of those patterns. Hence, again it seems it is more a matter of grade than of novel characters, at least in terms of geometry. Interestingly, allometry has a very minor role (if any) in intraspecific differences. In both species, shape variation and asymmetries are especially marked in the parietal areas.