You are right indeed.. it is more like a network of points requiring more energy at certain points ...
but some very specific areas deeicated to gather the information and produced an specific output (ot input in the case of the auditory cortex or the priamry visual cortex).

It seems that the most perpherial parts of the brain must be hihgly trained at the first stages of development.. and then proceed to get fairly fixed activity. Those areas can be studied in great detail..and the effects of the environment on this areas (learning) can be studied by doing experiments.

Since these specific areas have a high plasticity and highly depend on external input we just guess that the other parts that we see light-up in the fMRI are like mega-complex network of subunits workign hierarchialy and much more plastic than those peripherial areas.

It is really as amazing as you indicate... and more :)

A pleasure

I therefore claim to show, not how men think in myths, but how myths operate in men's minds without their being aware of the fact. Levi-Strauss, Claude