synaptic plasticity question, etc.

Jeffrey Rawlings rawlings at
Thu Feb 10 17:20:51 EST 1994

exb0405 at (BARRY MANOR, NO DOUBT.) writes:

>Something I'm curious about.  During the course of the adult lifetime, say even
>from minute to minute, does synaptic topography change dynamically ?  Are
>synapses 'broken' and formed as part of normal ongoing brain function ?

I would say "probably."  A couple of relevant lines of research:
	-In developing chick optic tectum, Scott Fraser and 
colleagues have imaged individual axonal arbors on a time scale
of an hour (maybe finer, now).  The results:  there are different
classes of branch points with different lifetimes, and you can
get very significant remodeling of entire arbours over fairly short 
time spans.  There is of course the assumption that these branches
actually contain functional synapses, and this is in developing, not 
adult, chick.

	-In adult monkey, Mike Merzenich has demonstrated large changes
in the receptive fields and maps in somatosensory cortex following
training of the monkey.  These changes occur (I think) on the order of 
weeks-months, although some may be faster.  Presumably, synapses
would have to be formed and broken on a large scale to get these changes.

>When speaking of 'protien systhe{is' as a basis for some aspects of memory,
>what exactly is meant ?  

I'm not sure, but this could be a reference to some forms of long-term
potentiation (LTP).  LTP is widely thought to be involved is some aspect
of memory, but it's role is still unclear, I think.

>Barry Manor  Physiologist Cognitive Neuroscientist Biomedical Engineer.
>             PhD Student in Medicine @ University of Sydney, Australia.
>             Generally Confused, Lover of Bicycles, Bach and Beethoven.
>   DoD #620  'Zeph' Kawa Zephyr 750.  She torques, I listen.
>     E-mail: b.manor at  (University of New South Wales).

Jeff   (rawlings at
"Would you tell me, please, which way I ought to go from here?"
"That depends a good deal on where you want to get to," said the cat.

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