On Tue, Jan 15, 2013 at 5:08 AM, Roger Clough <rclo...@verizon.net> wrote:

> How large (program length ?) a Turing Machine would you need to think ?
> Is complexity an issue with human thinking ?
> Is the brain's memory large enough to hold a lifetime of experiences ?
> http://www.scientificamerican.com/article.cfm?id=what-is-the-memory-capacity
> "The human brain consists of about one billion neurons.

Cats have about 1 billion neurons.  Humans have about 100 billion
(according to most sources I've encountered).

> Each neuron forms about
> 1,000 connections to other neurons, amounting to more than a trillion
> connections.

I've actually heard the number is closer to 10,000, with about an average
of 7,000 connections per neuron.  So there are about 10^15 connections.

> If each neuron could only help store a single memory, running out of space
> would be a problem.
> You might have only a few gigabytes of storage space, similar to the space
> in an iPod or a USB
> flash drive. Yet neurons combine so that each one helps with many memories
> at a time,
> exponentially increasing the brain memory storage capacity to something
> closer to around
> 2.5 petabytes (or a million gigabytes).

The above paragraph doesn't make much sense.  I think their mistake was
considering each connection to only equal one bit of memory, where as there
are probably many important attributes for each neural connection.  If each
connection required 1,000 bits to describe, then the amount of memory
necessary to store all important details regarding a brain's organization
would be 7000 * 100 billion * 1000 bits = 77.7 PB.  About 2,000 4 TB hard

> For comparison, if your brain worked like a digital video
> recorder in a television, 2.5 petabytes would be enough to hold three
> million hours of TV shows.
> You would have to leave the TV running continuously for more than 300
> years to use up all that storage. "
I work for a large scale storage company.  Some of our customers today have
systems large enough to store an entire human brain (according to the above
estimates).  As computer power continues to double, we may in 15-25 years
have "thumb-drives" which could store an entire map of someone's brain.  It
would be much cheaper than cryonics. :-)


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