Counting
: synapses is relatively easy -- there are about 10^14 of them in the
: -- Bill Skaggs
I'd hesitate that counting all of the synapses in the human brain is a
relatively or otherwise easy task. The numbers I always see quoted in
the literature as to the number of synapses in the human brain is
performed through averaging. I am sure you are not implying that someone
somewhere has sat down at their microscopes with a billion and more brain
slices counting synapses.
After realizing that these averages are taken from different locations
in the brain (Cortex vs cerebellum, limbic vs medullary.. etc), we have
to also take into account that a good deal of our observed memory stems
from learned tasks and preprogramed motor skills (eg. typing my name on
the keyboard). Do these skills actual require memory? And do all the
multitude of synapses that fire in the process of creating this task
constitute cerebral, cerebellar and spinal synapses within your count.
Oh, wait.. now, I'm confused. The count always seems to be cortical (or
at least synapses within the cranium) as an estimate. What about patern
generators in the spinal cord? What about the multitude of reflexes that
never make it to the brain? I do not think that an estimate of the
number of synapses is in any way relative to a level of storage.
Secondly, the number of synapses do not relate to memory. Memory, for
the sake of this argument, is located within the hippocampus lets say.
Well, there is a huge portion of the brain that we will not be adding up
synapses in if we were to only contend with the idea of 'how much memory
does the brain have in computer terms'.
Finally, the processes of the brain are not just storage and memory per se.
Instead I think if you were to make any correlations to the number or
synapses, cortical density, electrical stimulation concentrations through
functional MRI etc.. to a 'computer' then I believe you must take into
account all elements of the processing of both a computer and the brain.
This would not just involve the number of synapses but how many fire for
one function vs how much of the a computer would be required for the same
function. (using a previous example of a visual field for 1 sec.) how
many neurons fire in the scanning of a visual field for one second,
examine recall of that one event (basically imposible to filter out all
other events in the human brain.. but for sake of comparrison) and then
perform the same task with a camera -> computer for processing and
storage and recall. I do not think that another analogy can work as well
as isolating single events and comparing.
CH
