> The beginning state of the brain (at least before birth,
> or better, before any actual inputs arrive) we should
> in principle be able to deduct from the information
> stored in the DNA. (The DNA contains about 10^10 bits)
I think this is wrong, since the genetic information is just the basic
rules to grow the brain, the exact structure is laid down in an
emergent fashion most likely very dependent on the environment; brain
growth creates information.
> Assumed we would connect all sensory nerves to a computer.
> Assumed the steps of the DACs are sufficiently small to
> not be noticed by the brain. The question then is:
> how much information per unit of time do I need to
> simulate the real life environment of a human individual
> in such a way that his brain will not notice the difference.
A quick and rough estimate (I can get real numbers with some effort,
but right now I'm lazy) is that there are around 2 million axons from
the eyes, around 6 million axons in the spinal cord, one million axons
in the auditory nerves and lets add one million for the rest of the
brain nerves. That makes 10 million axons of sensory information. The
normal activity for neurons lie beneath 1 KHz, so an upper bound on
the input would be 10 billion bits/s.
That makes around 10^14-10^15 bits per day, or 10 terabytes. This is
most likely a big overestimate (neural activity is sparse, there are
lots of correlations in the input etc). Over a lifetime that would be
10^18-10^19 bits. This is an upper estimate of the human capacity.
> An information input of 50 gigabytes per day results
> in a total of approximately 10^16 bits after an average
> human life time. The 10^10 of the DNA are much less and
> can thus be neglected.
But we do not store this flood of information, in fact most of it is
quickly removed. Only the salient information is retained and
amplified in the brain, and it is from this we learn. Of course, we do
not have good figures of how much this is.
My personal estimate for the human capacity is around a bit per
synapse (based on assumptions from neural networks), there are around
10^14 synapses, making a capacity of around 10^14 bits.
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