From: Anders Sandberg (asa@nada.kth.se)
Date: Sat Oct 02 1999 - 10:52:41 MDT
"Robert J. Bradbury" <bradbury@www.aeiveos.com> writes:
> I think we need a quick seminar from Anders on the possible differences
> in how the brain uses LTD & LTP.
Glad to be of help :-)
LTP = Long Term Potentiation occurs when two connected neurons (call
them A and B) are active together, especially if the presynaptic
neuron A is activated at a high frequency for a while. The signals
caused on the B side of the synapse by neuron A will become stronger
after this treatment, it has been "potentiated". LTD = Long Term
Depression occurs when the presynaptic neuron is activated at a low
frequency; this weakens the signal, and we say the synapse has been
depressed.
Neuroscientists love the LTP/LTD pair, since they seems to be a
reasonable basis for memory implementing Hebb's rule ("neurons that
fire together wire together"). LTP makes correlated neurons connect
together, while LTD makes anti-correlated neurons decrease their
connections. With just LTP, the network would likely work less well
because synapses would be "filled up" and cannot easily be re-used,
while LTD enables erasure as things change. In fact, some studies
suggest that LTD is more important than LTP for certain tasks; I'm not
sure about that one yet.
-- ----------------------------------------------------------------------- Anders Sandberg Towards Ascension! asa@nada.kth.se http://www.nada.kth.se/~asa/ GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y
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