> Anders responds:
> >Actually, there are some neurons that spontaneously will fire, even
> >if they have no inputs. So likely they will start spreading patterns
> >of activation, which will "bootstrap" from a coma-like state to a
> >sleeping to a waking brain.
>
> Hm. This sounds very mysterious to me. Let's see if this works
> any better:
>
> *** LAYMAN'S TERM ALERT ***
>
> Think of neurons as semipermeable membranes which are permeable to
> positive ions in one direction and to negative ions in the other
> direction. As soon as they are properly arranged and the temperature
> is raised to where ions can move around, they start getting "pumped"
> to opposite sides of the membranes. At some point, like the point at
> which a spark jumps a gap, the difference in charges is enough that
> the neurons "fire". Various neurons will fire in various places,
> and soon, due to the physical properties of neurons (ion permeabilities,
> chemical densities, synapse sizes, configurations of bumps on the ends
> of axons and dendrites, etc.) the firings start to form patterns and
> you're off and running (as it were).
Quite right, and good science popularization.
Usually neurons just remain in the "pumped" (hyperpolarized)
state until they get a signal that is above a certain threshold, but
some neurons occasionally randomly fire (perhaps due to noise or their
structure), and some neurons seems to be naturally pulsing. There are
even some neurons that fire not when inhibition from other neurons is
lifted.
-- ----------------------------------------------------------------------- Anders Sandberg Towards Ascension! asa@nada.kth.se http://www.nada.kth.se/~asa/ GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y