Effects of Transcranial Direct Current Stimulation on Brain Electrical Activity, Heart Rate Variability, and Dual-Task Performance in Healthy and Fibromyalgia Women: A Study Protocol.

People with fibromyalgia could experience physical and cognitive impairments. Furthermore, when performing two tasks at the same time, people with fibromyalgia showed a higher dual-task cost compared to a single task than healthy people. This may result in poorer performance of activities of daily living that are commonly presented as a combination of two or more tasks. Transcranial direct current stimulation (tDCS) is a promising nonpharmacological therapy. However, there is controversy regarding the intensities and the effectiveness of this therapy. Thus, the present study will aim: (1) to compare the effectiveness and the impact of two tDCS intensities (1 mA and 2 mA) on cognitive, motor, brain functions, and cardiac autonomic modulation; (2) to study the impact of tDCS on the dual-task performance and creativity after applying tDCS in dorsolateral prefrontal cortex. In this study, 26 women will participate and will be divided into two groups: women with fibromyalgia (n = 13), and healthy controls (n = 13). A reduction in cognitive-motor interference in dual-task performance is expected, as well as a modification in neurophysiological parameters and an improvement in cardiac autonomic modulation. Lastly, no different effects are expected depending on the stimulation intensity applied. The obtained results will help to determine if tDCS in the dorsolateral prefrontal cortex could improve the occupational performance of women with fibromyalgia.