Gánovce

The natural endocranial cast of Gánovce was found in 1926 in Slovakia, and dated to 105 ka. Although the surface is damaged, the endocast is pretty complete, and has some bony fragments of the braincase encrusted on the surface. Cranial capacity is approximately 1320 cc, and the endocast has a clear Neandertal appearance, with flat parietal lobes, projecting occipital lobes, and wide frontal lobes. Between the 40s and the 60s, Emanuel Vlček provided many comprehensive studies of the cast, including shape analyses based on superimposition criteria and outlines, histological and chemical surveys, and radiological considerations. However, the endocast is scarcely known because most of the articles were published in Czech and Slovak. We have now published a JASs report to briefly summarize the information available on this fossil, providing further metrics, new comments on the craniovascular features, and a digital reconstruction after tomographic scan.

Mind and Brain

Amazing special volume in Cortex: The Evolution of the Mind and the Brain. The issue is edited by Michel Thiebaut de Schotten and Karl Zilles, and it includes reviews articles and research reports on neuroanatomy, primatology, ecology, social cognition, networks, cytoarchitecture, neuroimaging, handedness, brain size and cortical folding. A great collection of papers and authors, indeed!

Paleoneurology at UCCS

At the end of August we will begin a renewed online course in Human Paleoneurology at the Center for Cognitive Archaeology of the University of Colorado Colorado Springs. Here a post introducing the course, and the information on registration and credits.

Monkeys’ parietals

Parietal lobes are specialized in primates, and particularly in humans. Nonetheless, the information on their anatomical variation is still scanty. In non-human primates, parietal cortex is investigated only in few species (generally, macaques) and mostly at the histological level. Now we have published a morphometric analysis on the parietal lobes of 11 cercopithecid genera. The study was performed on endocasts, as to broaden the conclusions to the fossil record too. Parietal differences among the main subfamilies have been described before, even in fossils, but without a detailed quantitative analysis. The main shape changes separate genera with large occipital lobes and small parietal lobes (cercopiths) from species with large parietal lobes and small occipital lobes (colobuses and baboons). Allometry is apparently not involved in this feature, and size increase is only associated with taller endocasts (probably due to cranial – not cerebral – factors). These different parietal-occipital proportions are supposed to be related to distinct cognitive organization, hypothetically influenced by diet and locomotion. It would be hence interesting to test the effect of different parieto-occipital ratios on specific behaviors and cognitive capacities. More body or more vision? Different views of the world …

Craniovascular traits

The vascular imprints on the endocranial surface, the diploic channels within the vault bones, and the emissary foramina of the cranial cavity, are used to make inferences on blood flow in archaeological and paleontological samples. Unfortunately, basic information on many of these craniovascular traits (variation, distribution, homology, development, influential factors and even functions) is still poor for our own species. It sounds unpractical to investigate a feature in a few broken bones of an extinct species, if the same information is lacking for many billions living individuals. A former study was focused on the parietal bone. Now we have published a comprehensive endocranial survey on these traits in two modern European populations, to supply more information on their variability and on the influences of skull size and proportions, asymmetry, or sex. Blood flow exchange within the endocranial cavity may be relevant for thermal regulation and brain cooling. The final aim is to establish what functional or structural factors are involved in the morphology of these vessels and of their bony traces, as to interpret differences in extinct species or past populations. Many of these features bridge interests in anthropology and medicine.

Electrodermal tools

Theories in extended cognition suggest that mind is a process generated by the integration among brain, body and environment (including technology). Actually, tools are integrated into the body structural and functional schemes when handled, and the central nervous system delegates some capacities to these extra-body peripheral elements. Haptics concerns the perceptual and somatic response during hand-tool interaction, bridging sensing and cognition. Electrodermal activity is as a quick and simple proxy for some kinds of cognitive reactions (like attention or general arousal), and can be used to test emotional changes during stone tool handling, according to different tool typologies. Now we have published a full research paper on electrodermal activity during Lower Paleolithic stone tool manipulation. There are subtle but significant differences between males and females, and between choppers and handaxes. Specific physical features of the tools do influence the electrodermal reaction. If the body-tool system is regulated according to a “prosthetic capacity” of our cognitive mechanisms, electrodermal feedback can supply a first glimpse to investigate changes and discontinuities into the archaeological record, following basic principles in psychology and electrophysiology. The main aim is clear:  to move cognitive archaeology into quantitative hypotheses testing.

Networks

Network analysis is nowadays employed in so many fields, ranging from economics to engineering, to investigate any kind of system in terms of its elements and their relationships. Sociology is probably the discipline that has mainly exploited and improved this approach, and all the complex methods and statistics behind it. In neuroscience, it is mainly used to investigate neuronal connections. The perspective supplied by network analysis is incredibly powerful because it allows localizing roles and constraints within very complicated systems. Some elements can be crucial as hubs of local influences, some others can be important as bridges between distant components. Some elements can be very sensitive to local changes, some others can be more independent from neighboring variations. Systems can be complicated because of the many elements and relationships (hundreds or thousands or millions of nodes) or because of the nature of their relationships (many variables influencing the relationships). Or both. In any case, network analysis is an amazing tool to step into the organization of functional or structural systems. When applied to anatomical elements, we can talk of Anatomical Network Analysis. In its basic form, nodes are the anatomical elements, and relationships can be just their physical contact. The network, therefore, represents a topological model, in which the position and neighboring properties of each component are the evolutionary result of a selection balancing the architecture of the system, generating at the same time limitations and constraints. In evolutionary neuroanatomy and paleoneurology, too often each macromorphological change in a specific cortical region is directly (and speculatively) interpreted as a functional (cognitive) adaptation. However, brain geometry is also influenced by skull constraints, and each cortical region is also sensitive to spatial variations of its neighboring cortical elements. Therefore, some anatomical changes may be due to intrinsic changes (for example, cell proliferation or growth), while others may be due to secondary extrinsic factors (for example, pressures and strains of the neighboring environment). In a first attempt to apply network analysis to brain macroanatomy, one year ago we analyzed the cortical organization as described by the traditional Brodmann map, finding an interesting correspondence with the general subdivision in “lobes” and cranial fossae, and further integration of the parieto-occipital block. We have now published a more detailed study, on the regions generally considered in evolutionary neuroanatomy and paleoneurology, as to characterize their architectural roles and relevance in terms of overall topology. The posterior cortex is more integrated than the frontal regions, with the precentral gyrus acting as a spatial hinge between these two districts. Topological complexity matches, in this case, sulcal complexity. The temporal cortex is particularly sensitive to distinct cortical influences. We also considered a preliminary model including the main endocranial (bone) elements, evidencing the role of the anterior fossa and frontal bone in influencing the prefrontal cortical morphology. This first targeted analysis represents an invitation to go beyond simplistic approaches to brain morphological changes in paleoneurology and evolutionary neuroanatomy. Yet, it is just a kickoff. More steps are on the way.


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