Connectome

"One of the things that people say about the human brain is that it is the most complex system in the universe, essentially because the number of synapses [connections between neurons] in the cerebral cortex is supposedly the largest. We still have to figure out exactly how numbers of synapses compare across species, but still, its synaptic connectivity requires an impressive amount of information to describe or to set up, and you can’t find that much information in the genome by itself. There are not enough genes, not even by a combinatorial code, to specify all the possible connections between neurons in the cerebral cortex. So the connectivity in the brain is set up initially with the basic biological instructions in your genome, but once that is done it changes through a self-organised process. How you use your brain specifies directly what your brain looks like. “You become more and more yourself as life goes by.” That’s the idea behind the connectome as Sebastian describes it: this highly personalised set of connections, this pattern that defines who you are. Over time, it becomes more and more personalised. You become more and more yourself as life goes by. As your brain gets around, it gets modified by its very activity. Which pretty much answers the question, or solves the paradox, of how could one possibly get this tremendous amount of complexity in the organisation of the human brain with just a handful of genes to set it up. This self-organisation of the brain defines its own connectivity pattern and actually defines the system. Your brain contains all the information that it has lived through."