Ask A Scientist© Biology Archive

Author:      fath
Text:        In terms of computer memory how much information can the human 
brain store?  Similarly, what is the processing speed and architecture of the 
brain?

Response #:  1 of 2
Author:      James Murray
Text:        Yours is a difficult question to answer, mainly because the human 
brain is the most complicated object in the known universe.  Consider that a 
human brain contains some 100 billion neurons.  And likely 500 billion or more 
supporting cells.  And each neuron is extremely complicated electrically.  
Each neuron has millions of channels in its membrane and each of those 
channels is a digital gate that can allow electrical current to pass.  The 
wiring diagram of a single neuron would be hopelessly complex.  The simple 
answer to your question is that nobody knows.  Information storage is easily 
defined in digital computers because one knows exactly how and where 
information is stored.  Not so with the brain.  We know some about how and 
where, but not enough to estimate how much information is up there in your 2 
pound universe.  Consider that if you know how to play baseball well, the 
entire rules book is stored in your brain.  And besides that, the ability to 
hit a baseball with a bat is also stored in your brain (the cerebellum most 
likely, although some simple information is stored in the spinal cord).  Think 
of all the face you would recognize.  One would likely require 1000's of bits 
of information to accomplish a single face recognition.  Our brain's capacity 
is vast, perhaps someone has tried to estimate its capacity, but I would guess 
not, since we are so ignorant.  Processing speed is also difficult to answer 
and the tasks the brain processes are hard to quantify.  Adding the digits 1 
and 1 requires not only the ability to add, but the ability to recognize 
shapes, contrasts and to remember that certain shapes represent numbers.  Some 
people are capable of doing mental calculations with the speed of some 
computers.  Although these people are rare, it is possible that all people are


capable of these feats with practice.  You might recall the movie Rain Man 
that portrayed a man who could remember cards so well he could win at gambling 
often.  As for architecture, here we know something, but certainly not enough.  
The human brain is both serial and massively parallel in its processing 
algorithms and in its structure.  Each neurons sends out 100's of outputs to 
many different neurons.  And each neuron receives thousands of inputs.  These 
inputs are integrated in a complicated analog process involving synapses and 
dendritic trees.  Once integrated, that information is relayed to a "spike 
initiation zone" where it is decided whether the neuron will send a digital 
signal or not.  The temporal pattern of those digital signals travels over 
axons and cross long (inches or feet) distances in the nervous system.  In 
general, information flows from sensors, into integrating systems of neurons, 
and then out to motor neurons and finally to effectors like muscles.  I could 
try to answer a more detailed question if you like.  But as I said, mostly we 
do not know much about the brain.

Response #:  2 of 2
Author:      wizkid
Text:        It is also interesting that most people may use less than 10% of 
their neural capabilities.  This figure was arrived at when head-trauma 
patients required the removal of nearly 90% of their cerebrum, and yet 
recovered and continued to lead normal, successful lives.  Of course, this may 
partly have been the result of the parallel capabilities of the brain, 
overlapping and "making up" for what was lost.  The closest computer 
approximation of a brain are neural networks.  These are a general 
approximation of what happens when you take neurons communicating downstream 
and process inputs to the neurons.  It seems like and exploding field with a 
lot of potential to answer questions like capacity and processing speed.  If 
one uses neural networks as a model, there are some things one can infer about 
a brain.  The brain probably does not store information as directly and 
accurately as a computer.  The more neurons one trains to recognize an input, 
the more accurately they can recognize this input (to a limit).  A brain 
includes a very robust and flexible input system, this means that a brain has 
to do a lot more with any one input that a computer usually needs to since any 
one input is a lot more complicated than a byte.  Most everyday stimuli/inputs 
to the are fairly complex and the brain uses a fair amount of capacity to 
decipher it accurately.  In contrast computer input is relatively discrete and 
simple.  So a computer can afford the luxury of responding with precisely 
accurate output.