Abstract :
[en] INTRODUCTION: Thanks to the improvements in intensive care, an increasing number of patients survive severe brain injuries and may remain in an altered state of consciousness. Today, there is still a lack of effective treatments for these patients. Transcranial direct current stimulation (tDCS) and music have both given prom-ising results in improving signs of consciousness separately. Since tDCS effects can be increased by other therapies, we decided to combine it with music in this first study on healthy subjects.
OBJECTIVE: This feasibility and neurophysiological study aims to compare the effects of four types of stimulation - tDCS combined with music, tDCS combined with white noise, music alone (sham tDCS), white noise alone (sham tDCS) – on cognitive and neurophysiological outcomes in healthy participants, with the hypothesis that tDCS and music combined might improve cognitive functions compared to the other condi-tions, and thus, could be tested as a therapeutic option for patients with altered states of consciousness in the future.
METHODS: In this randomized, controlled, double-blind, crossover study, 23 participants received the four stimulation conditions separated by at least one week of washout. We compared their performance on two cognitive tests, namely the Stroop test and 3-back test, before and after each condition. We used the Stroop test and the 3-back to assess executive functions and study behavioral aspects. We also used a 20-channels electroencephalogram (EEG) to investigate the neurophysiological correlates of music and tDCS.
RESULTS: The behavioral assessments did not show any significant differences between the four condi-tions. However, the neurophysiological analysis revealed that for the whole brain, the frontal and parietal ar-eas, and for the four studied frequencies (delta, theta, alpha and beta), there is a statistical difference between three conditions: - White noise (and sham tDCS) VS music (and sham tDCS)
- Music (and sham tDCS) VS music + tDCS
- Music (and sham tDCS) VS white noise + tDCS
Overall, we obtain the same results in the whole brain and in the parietal/frontal regions, suggesting a gener-alized effect. Delta and theta frequencies are decreased when listening to music, while alpha and beta fre-quencies are increased. The use of white noise has the opposite effects, and the addition of tDCS seems to have variable results.
CONCLUSION: In healthy subjects, a single session of tDCS combined with music does not increase cog-nitive functions, as hypothesized. Nonetheless, using music alone instead seems to be promising for increas-ing brain activity related to cognitive performances by means of an increase in frequencies associated with cognition. Even if the results might be promising, they come from a relatively small sample of 23 subjects and might not be sufficient to represent the general population.
