Posts Tagged 'subparietal sulcus'

Precuneus form and folds

bruner-et-al-aa2017One more paper on the morphology of the precuneus. This time we have analyzed a racially heterogenous sample, confirming that precuneus size is a major source of brain form variation also when a wider genetic variability is taken into account. It is a variation that is apparently independent from sex, race, or hemisphere, although males could have slightly larger proportions than females. A larger precuneus can be associated with additional folds, often in its anterior district, although this association is feeble. Geometric models suggest that the areas involved in this variations are the anterior-dorsal ones, roughly corresponding to area 7a. This area is the largest and more variable of the precuneus, and it includes the medial cortex but also the dorsal external cortex of the upper parietal lobule. It is functionally associated with the integration of somatic and visual information, and with self-centered mental imagery. These results also suggest that upper and lower areas of the precuneus should be considered separately when dealing with functional or evolutionary neuroanatomy. Our former papers on this topic concerned the shape of the precuneus, its cortical surface area, its sulcal patterns and  lateral extension, and the differences between humans and chimpanzees. Apart from the relevance in modern neuroanatomy, these same endocranial regions also display a corresponding spatial enlargement in modern human evolution.

Subparietal morphology

Pedro-Pereira and Bruner 2016In this last years we have been studying the morphology, surface and position of the precuneus in adult humans and chimps. This week we publish a survey on its coronal anatomy: lateral extension and sulcal pattern. The aim of this article is to provide a quantitative description of its parasagittal variation in terms of morphometrics and folding schemes. The subparietal sulcus is larger on the right side, and possibly larger in males. The size of the subparietal sulcus is not associated with the sulcal scheme, which is very variable even between hemispheres of the same individual. The height of the precuneus influences the outer cortical profile, but the morphology and width of the subparietal sulcus have no apparent effect on the external brain geometry. The precuneus in general influences the upper cortical shape, with scarce or no influence on the lateral outline of the upper parietal lobules. Therefore, shape changes in this lateral areas are more likely to be associated with changes of the intraparietal fold. Correlations between inner and outer morphology are useful to evaluate whether changes in deep anatomical elements can be indirectly evidenced in paleoneurology, through the analysis of the outer (endocranial) surface.


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