[MURG] Non-invasive 3-D Scanning

[Joseph J. Strout]

At 9:37 PM +0800 12/17/03, Major wrote:

>If acquiring a long term memory requires a structural change that
>would imply that C. Elegans, which has a completely fixed neural map
>(both within an individual over time and between individuals of the
>same sex), would be incapable of learning.

Not true.  The neuron types and positions are fixed, but the 
ultrastructure is not.

>I would have to look it up, but I'm pretty sure C. Elegans has been
>seen to learn.

It has indeed, but it's too small to study easily.  A better model is 
Aplysia (a sea snail), which has larger neurons and can be easily 
trained in a variety of ways.  Eric Kandel and others have shown that 
this learning is correlated with structural changes.  See, for 
example, <http://www.columbia.edu/cu/newrec/2412/tmpl/story.1.html>. 
Excerpts:

"Kandel went on to find that long-term memories cannot form without 
the activation of genes that promote the growth of new synapses 
between neurons, or nerve cells, in the brain.  ... CREB switches on 
dozens of genes that stimulate the growth of synapses, which lead to 
the formation of persistent, long-term memories. ... it is becoming 
clear that the CREB molecular switch for converting short- to 
long-term memory that Kandel identified in the sea snail is also 
important for memory storage in many species."

Cheers,
- Joe

-- 
,------------------------------------------------------------------.
|    Joseph J. Strout         Check out the Mac Web Directory:     |
|    joe at strout.net           http://www.macwebdir.com/            |
`------------------------------------------------------------------'