Comparison of Stimulation Patterns to Elicit Steady-State Somatosensory Evoked Potentials (SSSEPs): Implications for Hybrid and SSSEP-Based BCIs

The goal of this study was to systematically compare signal characteristics and performance of three stimulation patterns that have been used to elicit steady-state somatosensory evoked potentials (SSSEPs): no pulses, random pulses, and rhythmic pulses with a consistent pattern. These three different vibrotactile stimulation patterns were provided to the fingertips of five healthy subjects by a small solenoid-type vibrating tactor. The five subjects, who were blindfolded, were asked to selectively focus their attention to either left or right fingertip flutter sensations, according to the audible cue given. Results of this study showed that small solenoid-type haptic tactors can elicit SSSEPs near the contra lateral central brain areas. There were significant differences in the resulting signals between the three paradigms, with the rhythmic pattern showing the highest classification accuracy. Moreover, the accuracy of the rhythmic pulse pattern was significantly higher than with or without random pulse patterns for the majority of subjects. The results of this study should provide insights to future research of SSSEP based BCIs and hybrid BCIs that use SSSEPS as one type of brain signal for users who are unable to use visual BCIs.