"Growing" Brain Tissue A key insight is to take into account the fractal nature of how the brain  grows  (like any other tissue) from a single stem cell. Model structure should reflect the way cells grow and connect rather than relying on mathematical structures like matrices. Connections  look  random but have an underlying fractal structure. On the other hand, the model needs to reflect the well known principle that "cells that fire together wire together". The fractal structure "explains" this rule in a physical way (cortical columns) but the brain can wire itself up in a way that might be seen as 4 dimensional. Connections are formed due to "closeness" in space as well as some kind of time function.  The model should assume some level of continuous growth. In the brain, new neurons are being created and others are dying all the time. It's not known how these new neurons find their place in the structures of the brain. Similarly, we know ...

A Popular Fairy Tale Comparing human brains to computers has become something of an industry lately. Like nuclear fusion, an emergent silicon mind seems to be always just around he next corner. The poster boy for this idea is Ray Kurzweil . If you want to watch a movie imagining precisely this vision, take a look at Transcendence . Transcendence is a tolerably good movie but brain capture fails in the movie for truly stupid reasons (plot spoiler) because it apparently fails to capture the "soul" and not due to any fundamental difficulty involved in creating a mind in a machine. The monstrously expensive and spectacular failure of the Blue Brain project was conceived by Henry Markham. You can view his  version of this fairy tale on TED.  [1] So How Big a Computer Do We Need? The 19 million volumes in the US Library of Congress represent about 10 trillion characters - 10,000,000,000,000 characters. To make the analogy even approximately apt, we need to imagine each character i...