Brain Vs. Computer, Round 979013
Ray Kurzweil's Singularity movement is predicated on the eventual ability (hence all the vitamins) to build empty simulacra of human brains into which our consciousness can be poured when our bodies fail, letting us live on forever. (Never mind the population nightmare that would result.) Many Singularitarians assume that with Moore's Law, technological advances will allow us to build a brain within 50 years.
Although no one really knows how much information the human brain stores, New York Times bloggers Sandra Aamodt and Sam Wang give it a guess in a must-read discussion of the electrical engineering and neuroscience of the Singularity. It's not often that you find both, so go read the piece.
The consensus among neuroscientists is that a chunk of brain the size of a thimble contains 50 million neurons.
The memory capacity in this small volume is potentially immense. Electrical impulses that arrive at a synapse give the recipient neuron a small chemical kick that can vary in size. Variation in synaptic strength is thought to be a means of memory formation. Samâ''s lab has shown that synaptic strength flips between extreme high and low states, a flip that is reminiscent of a computer storing a â''oneâ'' or a â''zeroâ'' â'' a single bit of information.
But unlike a computer, connections between neurons can form and break too, a process that continues throughout life and can store even more information because of the potential for creating new paths for activity. Although weâ''re forced to guess because the neural basis of memory isnâ''t understood at this level, letâ''s say that one movable synapse could store one byte (8 bits) of memory. That thimble would then contain 1,000 gigabytes (1 terabyte) of information. A thousand thimblefuls make up a whole brain, giving us a million gigabytes â'' a petabyte â'' of information. To put this in perspective, the entire archived contents of the Internet fill just three petabytes.
The upshot of this is that the brain manages to store that much information on 12 Watts (a computer that could do the same would require the power supply that drives Washington DC). It does so, however, by taking some notorious shortcuts: it encodes emotion to strengthen an event in memory, it is prone to prejudice and poor planning, it approximates shamelessly (hence a physicist's ability to "imagine a spherical cow"-- not exactly floating point operations, is it?).
So all this fetishizing the ability to build a human brain may be misguided. Because in order to get the amazing parts to work, we have to throw in the less amazing parts.
What Aamodt and Wang touch on is the idea that maybe replicating an exact human brain would be impossible-- and if it were possible, the result would not be a HAL-like Rainman-meets-Aspberger's superbrain, but a financially irresponsible, mildly racist, xenophobic jerk. What a depressing use of research money.
They liken our brains to 100-year old jalopies:
Because the brain arose through natural selection, it contains layers of systems that arose for one function and then were adopted for another, even though they donâ''t work perfectly. An engineer with time to get it right would have started over, but itâ''s easier for evolution to adapt an old system to a new purpose than to come up with an entirely new structure. Our colleague David Linden has compared the evolutionary history of the brain to the task of building a modern car by adding parts to a 1925 Model T that never stops running.
And what does starting over look like? What would the human brain look like if it had been designed from scratch?