On 13/03/2013 21:48, Matt Mahoney wrote:
A couple of updates to my paper on the cost of AI.
https://docs.google.com/document/d/1Z0kr3XDoM6cr5TgHH0GXQTjyikr7WpCkpWFn9IglW3o/edit#
1. I refined the hardware requirements by finding better estimates of
the number of synapses in the brain. The cerebral cortex has 16
billion neurons with 7000 synapses each, for 112 trillion. The
cerebellum has most of the brain's 86 billion neurons, but most of
these are granule cells (50 billion) with 80-100 synapses each, for a
total of 4-5 trillion synapses. This means that 1 petaflop and 100
terabytes of memory may be sufficient, about 1/10 of my previous
estimate. (The neuron count was done by liquefying a brain and
counting nuclei). Keep in mind that a 3 year old child may have
several times more synapses than an adult, so the solution might not
be so simple.
My source claims that synaptic density peaks at around age 2 (50% higher than
adults)
and is still high at age 7 (36% higher than adults), when the brain is quite
large.
- NEURAL CONNECTIONS: Some You Use, Some You Lose by JOHN T. BRUER
- http://www.oecd.org/edu/ceri/31709587.pdf
If accurate, that makes any net synaptic loss during development pretty modest.
Yes, the brain loses quite a few whole neurons during development, but I think
it must be making new synapses as it goes along about as fast as it loses them.
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|im |yler http://timtyler.org/ [email protected] Remove lock to reply.
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