"PerlTCL"  wrote
>
> What is the physical basis of memory (human brain)? Can someone give a
> brief review or progress so far. Thanks.
>
The brain consists of two basic types of cell, neurons and glial cells.
Basically the neurons do the information processing whilst glial cells
perform housekeeping tasks, transporting nutrients to the neurons and so on.
However current thinking is that glial cells may also play a role in
thought.
Neurons are like little telephone exchanges. They have input wires and
output wires. Each output wire, or axon, sends electrical pulses, called
action potentials, to other neurons. The axon joins the input fibre, or
dendrite, of another neuron at a synapse. Synapses can either excite or
inhibit the target neuron, making it more or less likely to fire.
If you are interested in computing, you can design logical circuits on these
principles which will perform calculations. However it is not fully
understood how complex behaviour is built up from these units.
Our best theory of memory is that the synapses change in strength over time.
So for instance stimulating the gill of the sea slug, Aplysia, will cause a
withdrawal response, but repeating the stimulus will lead to the response
becoming less and less marked (habituation). This can be explained by the
connection between the input nerve and the motor nerve becoming weaker as
the animal gets repeated harmless stimuli.

However this is still very speculative. What we certainly don't know is how
varying synapse strengths cause conscious recall in humans. However it is
likely that the synapse is the physical basis of memory.
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