Re: How many bytes can the human brain hold?

This is a tricky question, because the brain's architecture differs 
significantly from that of modern computers.  Furthermore, there's a lot we 
don't know.

First, the only number I can give:  the brain contains about 10^11 (100 
billion) neurons.

Now, on to the differences.

In a modern computer, the memory is separate from the central processing 
unit.  The CPU does things with information, while memory simply holds it.
In the brain, the distinction is not so clear.  It may well be that every
neuron is involved to some degree in processing, to some degree in memory.
For example, when you see a bicycle, the neurons involved in remembering
what a bicycle is might help activate other neurons involved in related
memories, such as your childhood bicycle or your thoughts on alternative
transportation.

Another difference is that, in a computer, memory cells are 
interchangeable.  A piece of information can be copied or moved from one 
location to another.  In the brain, it would be surprising to find two 
groups of neurons hooked up in exactly the same way.  (This makes science 
fiction tales of telepathy and mind transplants rather dubious.)

Putting a number on the amount of memory available is made more difficult 
by the brain's analog (as opposed to digital) nature.  Computers, of 
course, store things as digital on-or-off bits.  The advantage of this is 
that subtle variations in voltage don't alter the data:  if a bit appears 
to be "95% on", the computer can read this as "on".  The brain works in a 
much sloppier fashion, effectively using continuous real numbers.  There is 
plenty of noise in these numbers, though, so we can't say how many bits of 
data are stored in a neuron's activity level.

Long-term memory seems to be stored in the connections between neurons.  If 
we assume that the average neuron has 1,000 connections (not unreasonable) 
and that each of these connections stores one byte, then your figure of 100 
terabytes is reasonable.  However, I would doubt that we have access to 
this much data.  Computer memories contain cleanly delineated files, so we 
can say "find chapter 3" or "find the space battle program".  In the brain, 
everything is mixed together.  One effect of this arrangement is that 
sometimes we have difficulty accessing our memories -- the "tip of the 
tongue" phenomenon.

If you are interested in computer modeling of the brain, a classic (and 
easy to read) work is "Parallel Distributed Processing", by Rumelhart & 
McClelland.