X-Message-Number: 8405
From: Brian Rowley <>
Subject: Re: synapses and LTP (Thomas Donaldson)
Date: Sun, 20 Jul 1997 10:08:33 -0700

Thomas Donaldson wrote:
>As many have said, our long term memories are not stored electrically. The
>best current ideas for how such storage works is that it involves changes
>in the connectivity of our neurons, including (possibly) changes in 
>the individual synapses which mediate that connectivity. LTP, though it 
>may be a means for somewhat longer-term storage, is unlikely to be the
>means for storage of real long term memories. For one thing, most research
>on LTP looks at our hippocampus, which is actually a very small part of 
>our brain, unlikely to hold all our memories. What it can do, of course, is
>allow much slower processes needed for real long term storage to take 
>place --- after which it vanishes.

As far as electrophysiologists know, LTP (long-term potentiation) is
permanent (i.e., "indefinite"). It involves structural changes to the
synapse, e.g., the nerve terminal gets fatter. It involves biochemical
changes to the synapse, e.g., there is an increase in "second messengers"
such as nitrous oxide and protein kinase C. The result of these pre- and
post-synaptic effects is believed to explain the long term increase in
neuronal excitability. Potentiation occurs in all neurons, including motor
neurons, although it tapers off in motor neurons over time and is therefore
not called LTP. Brain neurons, not just hippocampal neurons, can undergo
long-term (indefinite) potentiation, and it is believed to be a way in which
neurons learn.

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