Submitted on March 2, 2009
Revised on April 8, 2009
Accepted on April 13, 2009
Brain polarization enhances the formation and retention of motor memories
Joseph Michael Galea1 and Pablo Celnik2*
1 Johns Hopkins Medical Institution
2 Johns Hopkins University
* To whom correspondence should be addressed. E-mail: pcelnik{at}jhmi.edu.
One of the first steps in the acquisition of a new motor skill is the formation of motor memories. Here we tested the capacity of transcranial direct current stimulation (tDCS) applied over the motor cortex during motor practice to increase motor memory formation and retention. Nine healthy individuals underwent a crossover transcranial magnetic stimulation (TMS) study designed to test motor memory formation resulting from training. Anodal tDCS elicited an increase in the magnitude and duration of motor memories in a polarity-specific manner, as reflected by changes in the kinematic characteristics of TMS-evoked movements after anodal, but not cathodal or sham stimulation. This effect was only present when training and stimulation were associated, and mediated by a differential modulation of corticomotor excitability of the involved muscles. These results indicate that anodal brain polarization can enhance the initial formation and retention of a new motor memory resulting from training. This process may be the underlying mechanisms by which tDCS enhances motor learning.
