Effects of transcranial direct current stimulation in brain-computer interface

The potential of brain-computer interfaces (BCIs) to replace lost neuronal function in the form of neuroprostheses is attracting much attention as a new technology. However, BCI performance varies among subjects, and the factors affecting BCI performance are poorly understood. Transcranial direct current stimulation (tDCS) is a non-invasive technique that moderates cognitive and motor function. Therefore, we investigated whether tDCS on the motor area enhances functional connectivity related to controlling an BCI and improves control performance. We found that functional connectivity between the motor area and both the caudate and cerebellum after stimulation were higher than that before stimulation, which suggests that stimulation may strengthen connectivity between basal ganglia and motor area. However, BCI performance after the intervention was significantly worse than that before, which conflicted with our hypothesis that stimulation would improve BCI performance. Participants were instructed to modulate their own brain relative to baseline using motor imagery. We suspect that the effect may have disturbed their brain self-regulation, because the stimulation affected signals not only during BCI control, but also during baseline. In the future, we will assess the mechanism underlying this decline in BCI performance to enhance BCI performance through finding stimulation which specifically affect BCI control.