HOW TO BUILD A BRAIN

‘The brain is the most complex structure in the known universe,’ says Allen Institute chief scientific officer Christof Koch. Here’s how to make one.

First, procure roughly 86 billion neurons (A), which are cells that collect information from other cells, via projections that look like tree branches (dendrites [B]) and shoot that information down itty-bitty cattle prods (axons [C]) using electricity generated by sodium and potassium ions.

Next, get some as yet unknown number of support cells called glia. These include oligodendrocytes, which wrap the highways of the longest, most important axons in fatty sheaths to speed up their electrical signals; astrocytes (D), which look like sponges and can communicate with each other; and microglia, which act as the brain’s private immune system.

Each neuron should have an average of 7 000 connections, mostly through synapses: empty space that must be crossed by chemicals. There are more than 100 of these chemicals (neurotransmitters) and many neurons release more than one.

All of your neurons and glia and other bits must selfassemble, and their connections should change based on what your brain encounters. Every single time your new brain does something it remembers later, such as reading this story, some parts of the network have to change permanently. Good luck!