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Showing posts from September, 2008


In 1949, Canadian psychologist Donald Hebb proposed that "When an axon of cell A is near enough to excite cell b or repeatedly and consistently takes part in firing it, some growth process or metabolic changes take place in one or both cells such that A's efficiency, as one of the cells firing B, is increased". (ref.) This idea is captured in the slogan 'Cells that fire together wire together'. A special set of molecules called neurotrophins play an important role in this. From Joseph LeDoux's book The Synaptic Self: When an action potential occurs in a postsynaptic cell, neurotrophins are released from the cell and diffuse backward across the synapse, where they are taken up by presynaptic terminals. Under the influence of neurotrophins, the terminals begin to branch and sprout new synaptic connections. Since only those presynaptic cells that were just active (that just released transmitter) take up the molecules, only they sprout new connections. activ…