Precuneus and superior parietal lobule: morphology and evolution in the human genus

Humans display larger and more complex parietal lobes, when compared with other primates. The superior parietal lobule is a region still poorly known in terms of comparative and evolutionary neuroanatomy, although at least its medial region, the precuneus, is apparently expanded in our species. In this article, I review twenty years of personal research on the morphology and evolution of this cortical element. The precuneus is particularly variable among adult humans, mostly in its dorsal and anterior areas. This large individual variability seems already settled at birth. During aging, this cortical region is particularly sensitive to atrophy and neurodegeneration. Its ventral areas are embedded in a complicated topological environment, suggesting spatial, metabolic, and vascular constraints. Human and non-human primates share a similar organization of the superior parietal lobule, although with different proportions. Even when compared with extinct hominids, the precuneus in modern humans looks more expanded. These changes are expected to be associated with some cognitive variations, possibly involving visuospatial integration, body cognition, mental imaging, and self-construction.