Mechanisms of use-dependent plasticity in the human motor cortex

Practicing movements results in improvement in performance and in plasticit y of the motor cortex. To identify the underlying mechanisms, we studied us e-dependent plasticity in human subjects premedicated with drugs that influ ence synaptic plasticity. Use-dependent plasticity was reduced substantiall y by dextromethorphan (an N-methyl-D-aspartate receptor blocker) and by lor azepam [a gamma-aminobutyric acid (GABA) type A receptor-positive allosteri c modulator]. These results identify N-methyl-D-aspartate receptor activati on and GABAergic inhibition as mechanisms operating in use-dependent plasti city in intact human motor cortex and point to similarities in the mechanis ms underlying this form of plasticity and long-term potentiation.