Selection process of synaptic connections

Rich nomore at spam.no
Fri Nov 19 00:03:28 EST 2004


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





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