From: Ramez Naam (ramezn@Exchange.Microsoft.com)
Date: Tue Feb 01 2000 - 10:21:00 MST
Thanks Anders, a note on your research below:
From: Anders Sandberg [mailto:asa@nada.kth.se]
> Ramez Naam <ramezn@Exchange.Microsoft.com> writes:
>
> > A word on effectiveness: <my summary snipped>
> As the resident memory researcher, I would just like to add that the
> above seems to fit my knowledge of the field.
>
> A further problem is that many of the memory enhancer drugs likely act
> by increasing the plasticity of the hippocampus either directly or
> through various relevance-signals. This would imply that they also
> make forgetting faster, at least in intermediate memory. I have some
> new results that place constraints on this, but I have to wait until
> the paper is accepted before I start explaining more. (sorry)
I haven't seen any published papers that explore this, so I look forward to
reading yours. That having been said, I'm fascinated by a paper that shows
something of the opposite. Specifically, Christoffersen seemed to show in
the Jun 98 issue of _Neuropharmacology_ that learning facilitated by
Piracetam was harder to extinguish than unaugmented learning, to the point
that it interfered with reversal learning (learning to make a different
choice in the previously learned situation). The abstract from Medline is
below.
Also, one tangential observation: The dosage levels they use in tests of
nootropics on laboratory animals are incredibly large. The experiment
below, for example, would correspond to at least 15g of Piracetam for a
human, or 6x the maximum recommended dosage.
<ABSTRACT
Neuropharmacology 1998 Jun;37(6):815-25
Piracetam inhibits Pavlovian extinction and reversal learning in a spatial
task for rats.
Christoffersen GR, Kemp A, Orlygsdottir G
Neuroscience Centre for Cognition and Memory, August Krogh Institute,
University of Copenhagen, Denmark. GChristoff@AKI.KU.DK
Young male rats, trained in a spatial three-choice test, showed improved
task acquisition after chronic treatment with piracetam (250 mg kg(-1)).
After reaching a learning criterion, one group of animals was observed
during Pavlovian extinction of the task skill and another group was assigned
to reversal learning. The rate of extinction was slowed down in piracetam
treated specimens compared to control animals. During reversal training, a
new choice had to be learned while the previously acquired choice was no
longer reinforced. Acquisition of the new skill was significantly impeded by
piracetam in contrast to acquisition of the first skill, which was
facilitated. Also during reversal learning, the piracetam treated group
persevered longer than the control group in repeating the first acquired
choice at the expense of learning the new choice. It is therefore suggested,
that the impediment of reversal learning was caused by inhibition of
extinction. In an open-field test, the time spent exploring in motion was
increased by piracetam while the velocity of locomotion was unaffected by
the drug. In a novelty test, piracetam increased the rate of loss of
interactions with the novel object.
/ABSTRACT>
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