Selection process of synaptic connections

Rich nomore at spam.no
Fri Nov 19 11:56:23 EST 2004


"Rich" <nomore at spam.no> wrote in message
news:u7fnd.106357$bk1.57913 at fed1read05...
> http://www.napa.ufl.edu/2004news/braindish.htm
>
> "Individual neurons soon begin to extend microscopic lines toward each
> other, making connections that represent neural processes. "You see one
> extend a process, pull it back, extend it out - and it may do that a
couple
> of times, just sampling who's next to it, until over time the connectivity
> starts to establish itself," he said. "(The brain is) getting its network
to
> the point where it's a live computation device."
>
>
> 1. What is going on when a neuron "extends a process" (sampling
neighboring
> neurons) before making its final connection? What exactly is it looking
for,
> just the nearest neighbor? They describe it as though the connections are
> searching for something in particular.
>
>
> 2. They have an array of electrodes connected to cells in a petri dish.
How
> are the neurons "trained" to know right from wrong?
>
> "The neurons then analyze the data and respond by sending signals"
>
> The neurons don't even know *what* they are analyzing, so how can they
> "respond accordingly"? For the flight path of an airplane (for example),
how
> do the cells know right from wrong or nose diving from flying straight...
> What sort of training is going on??
>
> In artificial neurons (programmed in software or on hardware) synaptic
> weights are adjusted by means of a training algorithm.. the contribution
of
> error from each neuron is calculated and synaptic weight changes are made
> afterwards in a backwards pass (back propagation). But what could be going
> on with the experiment on real live cells? Just by sending an electrical
> current as feedback, how do the neural cells in the petri dish know that
> they have done something correct or incorrect in order to make their
> adjustments?
>
> Thanks.
>
> Richard


Someone from the Georgia Institute of Technology replied to one of my
emails:

"We don't know what the neuron is looking for when it extends its processes,
but we assume it is sensing some cell-surface molecules of neighboring
neurons, and using those to decide whether or not to make a synapse."

I'm researching this. Does anyone have any references?

Thanks.

Richard





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