Tag Archives: Cerebellum

Woolly mammoth brain

Endocranial casts are usually the only resource for studying brain gross anatomy of an extinct species. However, sometimes, a frozen mummy can add information not only on the cortical features but also on the internal structures of the brain. Some years ago, Anastasia Kharlamova and Paul Manger published a study on the mummified brain of a Pleistocene woolly mammoth. This Yuka woolly mammoth specimen, dated approximately to 38,000 years ago, was determined to be an adolescent female aged between 6 and 9 years. Its mummified brain is unique in the state of preservation, allowing access to its external and internal morphology through the use of CT imaging techniques. Furthermore, it gave the opportunity to compare mammoths with extant African elephants’ brain, in order to characterize Elephantidae brain evolution, by determining whether elephant-specific features were already present in this specimen. The authors first compared the brains of the two species in terms of overall organization, concluding the Yuka mammoth displays the typical structure of the Elephantidae family. Direct volume comparisons were possible only for the structures which borders were clearly visible on the CT scans. The brain volume of the Yuka mammoth shrank during mummification, due to dehydration, and occupies only about 55% of the endocranial volume. Therefore, the calculated structure masses had to be corrected for such shrinkage. Moreover, due to differences in tissue fat composition, this shrinkage was heterogeneous, differing between hemispheres and between these and the cerebellum, which showed the least shrinkage. Based on subdural volume and on regression equations using extant mammals, the brain mass was determined to range between 4,230 and 4,340g. Given the average brain mass of an adult female elephant is only 300 to 400 g heavier, and that this specimen is immature, the values appear to be close to what would be expected for an adolescent woolly mammoth female. The size of the corpus callosum was also similar to that of female African and Asian elephants suggesting that, like elephants, mammoths also displayed sexual dimorphism in this structure. The comparable size of the amygdala suggests a similar organization of the limbic system, and the similarity in size and organization of the cerebellum point to a similar role in control of the trunk. This further indicates the Elephantidae family holds the largest cerebellum of all mammals, and that the cerebellar sensorimotor integration and learning movements of the trunk is a feature of this family. As the Elephantidae brain structure seems to be evolutionarily conservative, it can be assumed that the woolly mammoth could have achieved the same cognitive capacities as the extant elephants. However, further predictions of behavior and specializations would need a more detailed histological examination, which was not possible in the Yuka specimen. Nonetheless, this study provided an exceptional glimpse into the brain of an extinct species, and helped extending the understanding of the Elephantidae family.

 

Sofia Pedro

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Chiari malformation and the posterior fossa

SyringomyeliaChiari Malformation type 1 (CM-I) is an anatomical hindbrain abnormality having various symptoms (headache, pain in the neck and shoulders) because of obstruction of cerebrospinal fluid circulation and compression of hindbrain tissues such as the cerebellum, brain stem and spinal nerve. Most CM-I have syringomyelia. There is no direct test for CM-I and often symptoms are misinterpreted. Indicating tests are MRI, CT, neurological tests and CINE PC MRI. Treatment is a surgical operation called “posterior fossa compression”. Recently, researchers from the Netherlands and Turkey conducted different studies to examine this disorder. Akar et al. tested the usefulness of fractal analysis to examine the morphological complexity features of CM-I. Fractal Dimension (FD) analysis conducts the structural differences between patients with MCI (n=17) and healthy control subjects (n=16). Results showed that patients with CMI have larger cerebellar gray matter (GM) areas compared to controls, in contrast to other studies. FD could be a significant indicator for brain abnormalities in the cerebellum of CMI. It seems to be the case that the higher the FD value of cerebellar , the more complex object structure was. Rijken et al. found by examining 28 not operated, 85 operated craniosynostosis patients and 34 control that development of CMI is more likely to be supra tentorial. Craniosynostosis patients with CMI have similar cerebellar volume (CV) and posterior fossa volume (PFV) to control subjects, but they do have a significantly higher CV/PFV ratio. A higher CV/PFV ratio can be regarded as a predisposing factor for the development of CMI. In the end Rijken et al. advise to focus more on the skull vault itself.

Johannes Freiherr von Boeselager