The brain is like crumbled paper

This paper shows that the crumpling of our brain is much simpler than we thought . The crumples in our brain are just like the ones in crumpled paper. Bruno Mota and Suzana Herculano-Houzel find that our brain shares something in common with crumbled balls of paper - both did not evolve their folds in response to natural selection of their environment.

This paper shows that the crumpling of our brain is much simpler than we thought. What sets humans and other mammals apart is the ability to crumple our brains into our heads - by means of cortical folding. It had long been theorized that the folding - which is different for different animals - has something to do with ontology or evolution to control the number of neurons in parts of the brain. Now, it seems, its just basic physics!

The authors use datasets from about 14 papers that include all sorts of information including the number of cortial neurons, the cortial surface areas, brain volume, brain mass, thickness, etc. They find some correlation between these variables, but often with many outliers and generally low correlation.

However, the authors find that the total surface area scales with the exposed surface area as a power law - indicating a self-similarity in the surfaces. That is, the brain is a fractal with dimension ~2.5. What other physical objects have a dimension of ~2.5? Well, crumpled sheets of paper do!

This paper may be of most interest to scientists who are pursuing the evolution of cortical folding - maybe they should stop pursuing that now…

Since the general mechanism is in place for understanding brain folding, we can now understand better what goes wrong and why - which could be very beneficial informaiton for determining the origins of diseases.