| www.scinexx.de The Wisssensmagazin |
exercise of power really the master?
mechanism of long-term learning revealed
practice makes perfect - this is the motto of the frequent repetition is often seen as the best way to learn. American neuroscientists have been more surprised, therefore, when they found in experiments that at the level of individual synapses, the connections between nerve cells, a frequent repetition initially seemed to have more negative effects. In the journal "Science" they now report on the mechanism behind this seemingly paradoxical effect.
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| research landscape brain © Hemera |
Previous studies of the neuroscientist Alison Barth of Carnegie Mellon University had already shown that there is a correlation between the variability of the synapses and learning and memory. By common doctrine reinforces repeated practice of an activity or task specific synaptic connections, thereby improving the subsequent recall of that benefit. What is the mechanism, however, the long-term learning was facilitated by repetition, until now largely unknown.
Dr. Jekyll and Mr. Hyde
Barth and her team have now discovered that a receptor for the substance N-methyl-D-aspartate (NMDA) for this learning between a "good" and a "bad "Role changes, similar to a kind of "Dr. Jekyll and Mr. Hyde ". After initially promoting the receptor synapse connection, after a certain time but the effect is reversed and the receptors begin to weaken the synapses and even seemed to inhibit further learning. It is exactly this effect can be observed in practice. Instead, the memory also benefits later by frequent repetitions.
"We know intuitively that we are better the more we practice something," said Barth. "So there had to be something that even after the NMDA receptors strengthened their function changes over, the synapses continue." But what? To find out, the researcher focused on the cerebral cortex, the area in which takes place especially the slower, but long-lasting learning. It found that actually take place there as well other molecular processes in the brain regions responsible for the rapid, short-term learning, such as the hippocampus.
To move closer to the bottom of the case, Barth blocked in a series of experiments systematically different receptors in the brain, including the NMDA receptor and observed the effect on the long-term learning. She used this transgenic mice in which specific genes for the disabled individual receptors or activated were.
A second receptor mixed with
It was found surprising: It is true that the NMDA receptor for the beginning of the synapses, thus strengthening the successful learning critical, but after this initial phase was a second receptor into the game. This so-called metabotropic glutamate receptor (mGlu) seems like later in the learning phase, the debilitating effect of the NMDA receptor and takes the strengthening of synaptic connections.
"The neural mechanisms of learning and memory have been little understood," said Barth. "Because we the interaction between NMDA and mGlu receptors have revealed, we can now better understand how we learn. Perhaps we could even one day help to understand the disease better, are lost in which learning and memory, such as Alzheimer's. "
(NPO, Carnegie Mellon University, 08.01.2008)
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