On 13 Sep 1995, tareq i. j. albaho wrote:
> i have a question concerning hebbian learning ...
> in this model, the connection between two "neurons" is strengthened if
> both neurons are firing, and this leads to learning.
>> however, only recently i read that there is no direct experimental
> support for the hebbian model of neural plasticity.
Actually, there is quite a bit of evidence for a Hebb-like learning rule
in LTP (long-term potentiation); see Brown et al, "Hebbian synapses:
Biophysical mechanisms and algorithms", Annual Review of Neuroscience,
13:475-511 (1990) for a review.
The key difference is that actual action potentials ("firings") are not
required in the postsynaptic cell; rather, depolarization is all that's
needed. But this may be a minor point for your purposes.
All forms of LTP seem to depend on an increase in intracellular calcium
concentration in the postsynaptic neuron. In NMDA-dependent LTP, NMDA
receptors (which require both depolarization and synaptic glutamate)
allow the calcium influx; in non-NMDA LTP, voltage-gated Ca++ channels
may be involved.
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| Joseph J. Strout Department of Neuroscience, UCSD |
|jstrout at ucsd.eduhttp://sdcc3.ucsd.edu/~jstrout/ |
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