Re: NEURO: Advanced neurons?

Anders Sandberg (
Mon, 17 Mar 1997 16:19:19 +0100 (MET)

On Sun, 16 Mar 1997, The Low Golden Willow wrote:

> There's not just trickier to figure out; there's requiring more data for
> storage. John and Eugene have had their debates on how much data the
> brain encodes; the article seems to be evidence for Eugene's position.
> And it may argue against Drexler's extreme miniturization ideas; the
> brain could be less shrinkable.

I don't know how shrinkable the brain is, but being the brother/collaborator
of an Amiga demo programmer I know that a clever hack can achieve plenty
of compression if you have the basic algorithm right. I'm fairly sure
that once we have suceeded at uploading, we will gradually find ways to
shrink the upload matrix.

Back to the subject: I think the truth is somewhere between Eugene
(neurons are tricky, simulate them all as carefully as possible) and John
(neurons are important mainly in groups) - neurons indeed do a lot of
amazing stuff, but they also work together in populations. Evolution would
favor beings whose minds had a fair bit of redundancy over beings where
every neuron matters (in situations where brain damage is likely during
the lifetime of the being). So Eugene is pointing out an upper bound to
upload matrix capacity, while John is speaking of the "compressed"
brain-algorithm (where we can chunk neurons).

As a neural networks/neuroscience person I would guess that these new
properties would not increase the upper estimate with more than a
magnitude. If we assume 10^11 neurons with 10^4 synapses each, and 100
parameters in each synapse (I'll chunk the synapses and dendrites they sit
upon into one unit here), we get 10^17 state variables. Nonlinearity,
dendritic computation and similar stuff just makes calculating the next
state more heavy, and doesn't increase the storage needs much. Each
update, (say) every millisecond might depend on the other states in each
neuron + signals from connecting neurons, giving around 10^26 flops.
Diffuse modulation doesn't increase the estimate much. Of course, this is
a very rough estimate and should be taken with a large grain of salt.

Anders Sandberg Towards Ascension!
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