A new PhD student in the team working on craniovascular anatomy! Stanislava Eisová was in our laboratory few years ago, publishing a paper on parietal bone and vessels in which she investigated correlations between craniovascular morphology, skull size, and bone thickness. She got a Master Degree in Anthropology of Past Populations at the University of West Bohemia, Czech Republic. Now she begins a PhD program on Anthropology and Human Genetics at the Faculty of Science of the Charles University, Prague. Her project will be on craniovascular traits, anthropology, paleoanthropology, and paleopathology. She will investigate craniovascular characters in normal samples, pathological conditions, and fossil specimens. The project is co-directed by Petr Velemínský.
In a recent study, Tsuzuki and colleagues analysed the co-development of the brain and head surfaces during the first two years of life using a sample of 16 infant MRIs, aged from 3 to 22 months. First, they digitized a set of cortical landmarks defined by the major sulci. Then they determined the position of cranial landmarks according to the 10-10 system, a standard method to place electrodes for electroencephalography, using nasion, inion, and the pre-auriculars as a reference. Besides analysing the spatial variability of the cortical and scalp landmarks with age, they compared the variability of the cortical landmarks to the 10-10 positions, in order to evaluate the validity of the scalp system as a reference for brain development. For that, they transferred a given cortical landmark to the head surface by expressing its position as a composition of vectors in reference to the midpoint between the two pre-auriculars and to the three neighbor 10-10 points. The scalp-transferred landmarks were then transformed to the scalp template of a 12-month-old infant and depicted in reference to the 10-10 system.
Age-related changes in the cortical landmarks were most obvious in the prefrontal and parietal regions. As the brain elongates, the frontal lobe shifts anteriorly and the precentral gyri widen. In addition, the intraparietal sulci and the posterior part of the left Sylvian fissure move forward, suggesting relative enlargement of the parietal region in the anterior direction. The same result was obtained by our team by analyzing cranial and brain landmarks in adults: larger brain size is associated with a relative forward position of the parietal lobe. The scalp showed relative anteroposterior elongation and lateral narrowing with growth. Regarding the contrast between the cortical landmarks and the 10-10 system, the authors observed that the variability in the position of the former was much smaller than the area defined by 10-10 landmarks, indicating this system can be useful to predict the underlying cortical structures. Hence, they conclude that the changes in brain shape during development are well described by cortical landmarks and that the relative scalp positioning based on the 10-10 system can adjust to preserve the correspondence between the scalp and the cortical surfaces.
The world’s most detailed scan of the brain’s internal wiring has been produced by scientists at Cardiff University. The MRI machine reveals the fibres which carry all the brain’s thought processes. It’s been done in Cardiff, Nottingham, Cambridge and Stockport, as well as London England and London Ontario. Doctors hope it will help increase understanding of a range of neurological disorders and could be used instead of invasive biopsies …
[keep on reading this article by Fergus Walsh on BBC News]
A group coordinated by Dr. Vera Weisbecker examined whether the evolution of mammalian brain partitions follows conserved developmental constraints, causing the brain to evolve as an integrated unit in which the partitions scale with brain size. According to this ‘late equals large’ hypothesis, the timing of neurogenesis predicts the size of the partition such that later and more extended neurogenesis produces larger partitions due to the production of more neural precursors. In order to investigate the impact of neurogenesis on patterns of brain partition growth, the volumes of the whole brain and major partitions were reconstructed from soft-tissue diceCT scans of three marsupial species, including individuals with ages ranging from 1 day to adulthood. They tested three hypotheses consistent with a conserved brain partition growth: H1 postulates that partition scaling during development reflects the evolutionary partition scaling, and thus growth patterns should be uniform between species; H2 assumes that a neurogenesis-driven pattern of partition scaling is predictable from adult brain size, i.e. brain partitions scale with brain size; and H3 states that growth with age might differ between species according to brain size and/or neurogenetic events. Regressions of log partition volume against log rest-of-the-brain volume (whole-brain volume minus partition volume) showed significant interspecific differences in slopes and intercepts of most brain partitions, indicating diverse scaling patterns between species, which could not be predicted by adult brain size, as the smallest-brained species had intermediate slope to the other two. Growth curves of log partition volume against age were similar in all partitions within-species, but differed between species, particularly in growth rates, with the species with intermediate brain size having slower rates than the other two. Differences in growth patterns do not seem to be related to neurogenetic schedule as largest partitions are not especially late in their development and important maturation processes, like eye opening, occur closer to the end of the growth phase. Thus, none of the hypotheses are supported by these results, challenging the conserved neurogenetic schedules behind the evolution of mammal brain partitions. Moreover, the authors found high phylogenetic signal in brain partition scaling, revealing that a large part of the scaling relationship between brain and partition volumes is explained by phylogeny, which is more in agreement with a mosaic evolution of brain partition sizes, stressing its biological meaning and the level of mammalian brain plasticity. However, the intraspecific regular partition growth curves led the authors to contemplate the existence of an early brain partition pattern regulated by regional gene expression, and propose that further studies of brain partition evolution should integrate developmental neuromere expression models, neuron density, and patterns of neuron migration.
A perspective review on cerebellum and Alzheimer’s disease, coordinated by Heidi Jacobs …
Jacobs H.I., Hopkins D.A., Mayrhofer H.C., Bruner E., van Leeuwen F.W., Raaijmakers W., Schmahmann J.D.
The cerebellum in Alzheimer’s disease: evaluating its role in cognitive decline.
(and here a post on cerebellum and paleoneurology …)
The Finite Element (FE) method has increasing application to biological sciences but frequently lacks proper validation by robust experimental research. One aspect of particular biological and bio-mechanical importance is growth of the human infant skull. Specific local changes during growth of the infant skull are largely unknown with only the general rate of cranial increase from 25% at birth to 65% of the adult size by age six. The potential adverse effects of any abnormalities in infant skull growth is difficult to approximate if the isolated local areas likely to be most impacted are not accurately known. If properly validated, computer simulated modelling such as Finite Element methods would be invaluable in surgical settings. A new comprehensive study focusing on human infant cranial vault expansion utilized robust laboratory experiments of a fetal skull (ex-vivo), replicate physical model (in-vitro), several FE models (in-silico) and a sample of micro-CT infant skulls (in-vivo). The first validation tested a physical model against a FE model (A) in which the cranial base and facial bones formed a single structure with only the cranial vault comprising individual bones. The FE model (A) over-predicted size changes to the anterior of the skull especially near the orbits and mediolateral expansion of the skull. The second validation tested in-vivo models against an FE model (B) in which the only the facial bones formed a single structure while the vault and cranial base comprised individual bones. All analyses associated discrepancy between the FE model (B) and the in-vivo models with age-related changes. As age increased, the regions under-predicted by the FE model (B) were first the orbits and upper vault before tending toward the cranial base, while the regions over-predicted by the FE model (B) were focused on the anterior and posterior fontanelles.
This validation study showed that FE modelling could be used to approximate growth in the human skull with only small discrepancies. The differences between the predicted ranges of growth (FE models) and the observed growth (in-vivo models) was explained by assumption of isotropic brain expansion which simplified the highly complex and uneven growth rates in real brain expansion. The artificial construction of a single structure representing the facial bones added further constraints. The development of more advanced simulations could narrow the discrepancy between expected and observed growth patterns allowing a more accurate representation of human skull growth.
The human brain is the most expensive and costly organ in terms of energetic resources and management. However, the current understanding of its sophisticated thermal control mechanisms remains insufficient. Wang et al., 2016, have reviewed the most recent studies on brain thermoregulation and examined the anatomical and physiological elements associated with selective brain cooling. Modern humans have a brain that is approximately three times larger than a primate with a similar body size, which uses 20%– 25% of the total body energy compared with a maximum of 10% in other primates and 5% in other mammals. The evolution of a large and expensive brain in modern humans effectively influences critical factors such as temperature, and functional limits can affect cerebral complexity and neural processes. Brain thermoregulation depends on many anatomical components and physiological processes, and it is sensitive to various behavioral and pathological factors, which have specific relevance for clinical applications and human evolution. The anatomical structures protecting the brain, such as the human calvaria, the scalp, and the endocranial vascular system, act as a thermal interface, which collectively maintains and shield the brain from heat challenges, and preserves a stable equilibrium between heat production and dissipation. Future advances in biomedical imaging techniques would allow a better understanding of the physiological and anatomical responses related to the cerebral heat management and brain temperature in modern humans.
Gizéh Rangel de Lázaro
New member of the lab! Annapaola Fedato did her master thesis on cognitive archaeology and visuospatial integration in our laboratory, as a student from the University of Padua (Italy). And now she will keep on working on the same issue with a PhD grant, dealing with experimental archaeology, affordance, and hand-tool relationships. About this topic, here a perspective paper on visuospatial integration and human evolution, and a review on visuospatial behaviours and fossil evidence. Because this blog deals mainly with brain and skull anatomy, she will be in charge of posting news and information on those brain areas involved in visuospatial functions. Welcome! [Affiliation Info]