| Autor: |
Ziemann, Ulf, Iliac, Tihomir V., Pauli, Christian, Meintzschel, Frank, Ruge, Diane |
| Předmět: |
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| Zdroj: |
Journal of Neuroscience; 2/18/2004, Vol. 24 Issue 7, p1666-1672, 7p, 1 Diagram, 1 Chart, 5 Graphs |
| Abstrakt: |
Learning may alter rapidly the output organization of adult motor cortex. It is a long-held hypothesis that modification of synaptic strength along cortical horizontal connections through long-term potentiation (LTP) and long-term depression (LTD) forms one important mechanism for learning-induced cortical plasticity. Strong evidence in favor of this hypothesis was provided for rat primary motor cortex (M1) by showing that motor learning reduced subsequent LTP but increased LTD. Whether a similar relationship exists in humans is unknown. Here, we induced LTP-like and LTD-like plasticity in the intact human M 1 by an established paired associative stimulation (PAS) protocol. PAS consisted of 200 pairs of electrical stimulation of the right median nerve, followed by focal transcranial magnetic stimulation of the hand area of the left M1 at an interval equaling the individual N20 latency of the median nerve somatosensory-evoked cortical potential (PASN20]) or N20-5 msec (PASN20-5). PASN20 induced reproducibly a LTP-like long-lasting (>30 min) increase in motor-evoked potentials from the left M 1 to a thumb abductor muscle of the right hand, whereas PASN20-5-induced a LTD-like decrease. Repeated fastest possible thumb abduction movements resulted in learning, defined by an increase in maximum peak acceleration of the practiced movements, and prevented subsequent PASN20-induced LTP-like plasticity but enhanced subsequent PASN20-5-induced LTD-like plasticity. The same number of repeated slow thumb abduction movements did not result in learning and had no effects on PAS-induced plasticity. Findings support the view that learning in human M1 occurs through LTP-like mechanisms. [ABSTRACT FROM AUTHOR] |
| Databáze: |
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