Transcranial direct current stimulation (tDCS) can optimize beneficial effects induced by motor practice in patients with neurological disorders. However, possibly because of homeostatic regulation, the conditioning effects of tDCS are often imprecise and variable, limiting its therapeutic application.
The aim of the study was to explore the magnitude and direction of the after effects induced by physical activity (PA) on tDCS-preconditioned cortical excitability (CE).
First, a crossover experiment was performed with 12 subjects to determine whether a single session of low-, moderate-, and high-intensity PA on a treadmill modulates the motor CE measured by transcranial magnetic stimulation. In a second crossover experiment, we investigated long-lasting changes (until 90 mins) of the effects induced by PA (with intensities defined by the first experiment) on motor CE after the subject had been preconditioned by tDCS (using different polarities).
In experiment 1, we found that high- and moderate-intensity PA modulate the CE. Experiment 2 demonstrated that preconditioning the CE using tDCS homeostatically changes the direction and magnitude of after effects induced by subsequent PA plasticity caused by motor activity. In conclusion, the results suggest that the direction of after effects induced by the combination of physical exercise with tDCS on the CE is regulated within a physiologically defined range.
From the Applied Neuroscience Laboratory, Universidade Federal de Pernambuco, Recife, Brazil.
All correspondence should be addressed to: Kátia Monte-Silva, PhD, Applied Neuroscience Laboratory, Universidade Federal de Pernambuco, Department of Physical Therapy, Av. Prof. Moraes Rego s/n 50670-900 Recife, Brazil.
KM-S receives a grant from CNPq (308291/2015-8).
Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.
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