A Novel SSVEP-Based Brain-Computer Interface Using Joint Frequency and Space Modulation

Traditional steady state visual evoked potential (SSVEP) based brain-computer interfaces (BCIs) encode visual targets mainly with different stimulation frequencies. However, as more and more visual targets are squeezed into the limited stimulation spectrum in order to improve the BCIs' communication rate, the distinguishability among the neighboring targets with adjacent stimulation frequencies is to certain extent compromised. To solve this problem, in this paper a novel joint modulation scheme is proposed for the SSVEP-based BCIs, In the new scheme, visual targets are jointly encoded with different frequencies and different spatial forms. In this way, better classification performance can be achieved, especially for the neighboring targets. A four-target prototype system is developed and tested. The validity of the proposed new system using joint modulation is verified.