YOUR AMAZING AND MAGIC BRAIN

·        Cerebral cortex is the dominant subdivision. Including subcortical white matter, it occupies ~80% of brain volume but contains only ~20% of the brain’s 85 billion neurons.

o   The highly convoluted cortical sheet (~3 mm thick and ~1,000 cm² per hemisphere) contains ~150-200 cortical areas that differ from one another in connectivity, function, and architecture.  These areas span a ~100-fold range (0.2 – 20 cm²) in average size.  

o   Each cortical area varies 2-fold or more in size across the normal adult population. Data from the HCP may reveal whether specific behavioral capabilities are correlated with individual variability in the dimensions of functionally specialized areas or networks.

o   Individual variability in cortical folding and in areal boundaries relative to these folds is a major impediment to intersubject comparisons.

·        Cerebellar cortex occupies ~10% of brain volume, and contains 80% of the brain's total neurons, and is a sheet 1/3 as thick and half the surface area of cerebral cortex. Its lobes and lobules differ in their function and connectivity and are also variable across individuals. 

·        Subcortical structures occupy the remaining ~10% of brain volume but contain only ~1% of its neurons. They include hundreds of cortical nuclei and subnuclei, most of which are too small to be resolved by conventional in vivo neuroimaging.