Studies On Enhancing Performance Of Brain-computer Interface Based On Visual Evoked Potential Through Transcranial Electrical Stimulation

At present, brain-computer interface(BCI) is an active research topic that has attracted a lot of researchers. It can provide an innovative method for paralyzed people to interact with the outside world. In general, the performance of BCI based on electroencephalography(EEG) is still unacceptable, which has low information transfer rate and low classification accuracy rate. In previous studies, most researchers focus on developing advanced algorithms or designing new experimental paradigms to improve the performance. Recently, a neuromodulation technique, i.e. transcranial electrical stimulation(tES), may provide a new solution. It is believed that tES can regulate the brain cortex function, and improve the original EEG signals from the source. This work aims to explore the possibility on improving the performance of BCI based on visual evoked potential through tES technology.Firstly, BCI based on steady-state visual evoked potential(SSVEP) is selected for the study, which has high transmission in comparison with other BCIs. SSVEP based BCI can be divided into two categories: low-frequency visual stimulation and high-frequency visual stimulation, which have different performances. According to the current research, it is assumed that transcranial alternating current stimulation(tACS) can enhance the performance of SSVEP-BCI. The experiments of tACS for low frequency SSVEP-BCI are conducted on two groups(active and sham) with six subjects, the analysis show that there is statistical significance in the improvement after t ACS treatment. It also shows that tACS has different effect on low-frequency SSVEP-BCI with different visual stimulus. On the contrary, the present experiments show there is no significant improvement on performance of high-frequency SSVEP-BCI using tACS.Secondly, the effect of transcranial direct current stimulation(tDCS) on P300-BCI is investigated, and the experiments show there is significant difference between two groups(active and sham) in P300-BCI using tDCS, which indicates that tDCS can enhance the performance of P300-BCI.In addition, the experimental platform for SSVEP-BCI is developed to accomplish the basic function on controlling the wheelchair in practice, and the effect of tACS is preliminarily examined on the subjects for BCI controlled wheelchair.This work has combined theoretical analysis with experimental study, which can promote the clinical application of t ES to enhance the performance of SSVEP-BCI and P300-BCI in future.