Selection process of synaptic connections

Rich nomore at
Fri Nov 19 11:56:23 EST 2004

"Rich" <nomore at> wrote in message
news:u7fnd.106357$bk1.57913 at fed1read05...
> "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
> 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
> the point where it's a live computation device."
> 1. What is going on when a neuron "extends a process" (sampling
> neurons) before making its final connection? What exactly is it looking
> 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.
> 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),
> 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
> 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

"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?



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