The brain and its pathways

The human nervous system is by far the most complex product of evolution. Unexpectedly, what sets our brain apart from other animals is not the genetic divergence, estimated at little more than 1% compared to chimpanzees, nor the very short list of specialized neurons that arguably may exist only in humans. The complexity of our nervous system is generally explained by the remarkable number of neurons, estimated to be around 87 billion, and their ability to establish a staggering number of connections. Surprisingly, the brains of primates have fewer synapses per neuron compared to other species such as rodents, but their brains contain a greater total number of neurons. Among primates, humans have the largest brains, and this explains why our brain with a total of a thousand trillion connections is the most interconnected information-processing device on the planet. Hence, to understand how the brain-mind works we need methods to describe the anatomy of brain connections.