Neuroanatomical evidence suggests that we have relatively larger temporal lobes when compared with the apes’ allometric brain variation. Actually, there are also some form differences in our middle cranial fossa, housing the temporal lobes. However, the morphology of the middle endocranial fossa is influenced by many factors involved in the cranial base phylogeny and ontogeny, and we can wonder whether it strictly represents, in terms or direct linear variations, corresponding changes of the temporal lobes. The structural relationship with the underlying mandible is just one of the many non-neural influences of the middle endocranial area. Nonetheless, the middle endocranial surface can also provide information on the sulcal pattern of the temporal cortex, now further investigated by Antonio Rosas and Markus Bastir. In this case, the resulting morphology is more likely to be the direct consequence of brain morphogenesis and cortical organization, being less influenced by structural cranial constraints. That is, possible species-specific differences in the sulcal pattern can be more easily interpreted in terms of intrinsic brain factors (independently upon their functional meaning), more than in terms of extrinsic secondary consequences of the complex spatial dynamics of the endocranial base.
Posts Tagged 'functional craniology'
Tags: Antonio Rosas, functional craniology, Markus Bastir, middle cranial fossa, Temporal lobes
Tags: evolutionary medicine, frontal lobes, functional craniology, myopia, orbits
Paleoanthropologists are now fairly convinced about the importance of integration in biology and evolution. It is a rare pleasure to see such perspectives successfully applied to every-day life problems. Michael Masters, with a very well documented study on human evolution and functional craniology, suggests that myopia (the primary source of reduced vision throughout the world) may be the consequence of our recent anatomical evolution. Large brains placing the frontal lobes on the orbital roof and constraining the orbital space, while at the same time facial reduction provides further structural limitations. That is, in our species the orbit cannot acknowledge properly the morphological requirements of the eye. Brain and eye compete for space, and the advantages associated with the former are paid with the problems associated with the latter. The consequent packing deforms the eye, leading to vision problems. Allometric and brachycephalic proportions make the situation even a bit more difficult in women and East Asian populations. This hypothesis is an excellent example of interchange between evolutionary biology and medicine. Until now, myopia has been mostly studied considering the eye like an isolated unit. Masters has now provided a very effective example of how induction and deduction can be improved mixing fields, in this case integrating medicine with functional craniology and paleoanthropology. Interestingly, similar deformations associated with the frontal lobe spatial packing have been also described for some psychiatric disorders.