Neural specification?

Larry Lart larry at alphyra.ie
Fri Feb 15 08:32:45 EST 2002


yan king yin wrote:

>>   a. Dendrites Growth
>>         - Do they grow orientated under the action of a neighboor firing
>> axon ?
> 
> This question and the following ones concerns two phases, namely the
> developing and mature brain. In the developing brain dendritic growth
> is not solely determined by electrical activity. In the extreme case, one
> can observe neurons growing their characteristic dendritic structures in
> isolated cell cultures! Generally speaking, blocking electrical activity
> results in diminished dendritic trees.
> 
  What about trying to give a direction(in space) to dendrites growth 
using space orientated potentials ?

> I'm not sure what you mean when you say dendritic growth is "oriented"
> by electrical activity. There is some speculation that after long term
> potentiation (LTP), some dendritic spines split into two, forming
> bifurcating spines. This might be one way the dendrites grow.
> 

  What I don't understand/know is having this context in the mature 
brain:You have an axon in the vicinity of a few dendrites - if those 
dendrites grow either randon or by a rule(ie gene) the probability to meet 
in their way one of the the axon terminations and create a synapse could be 
quite low. right ? And what I was wondering if the directions in which 
those dendrites grow is determined by the electric potential fired by the 
neighboor axon in "void" ? like bellow  :

 firing axon [x]-> 

                       [z]<----dendrites normal grow direction          

 firing axon [y]->
        
  So now the question is: if the default grow path will be parallel with 
those to axons(or terminations of the same firing axon) those dendrites 
will never meet the axons. But if their direction is changed with the 
electric potential z(x,y) will make more sens ?! Like even the tree's roots
are a bit smart in this point of view ...






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