A comparison of two spelling Brain-Computer Interfaces based on visual P3 and SSVEP in Locked-In Syndrome.

[locked-in syndrome]

We study the applicability of a visual P 3 -based and a Steady State Visually Evoked Potentials (SSVEP )-based Brain -Computer Interfaces (BCIs ) for mental text spelling on a cohort of patients with incomplete Locked-In Syndrome (LIS ).Seven patients performed repeated sessions with each BCI . We assessed BCI performance , mental workload and overall satisfaction for both systems . We also investigated the effect of the quality of life and level of motor impairment on the performance .All seven patients were able to achieve an accuracy of 70 % or more with the SSVEP-based BCI , compared to 3 patients with the P 3 -based BCI , showing a better performance with the SSVEP BCI than with the P 3 BCI in the studied cohort . Moreover , the better performance of the SSVEP-based BCI was accompanied by a lower mental workload and a higher overall satisfaction . No relationship was found between BCI performance and level of motor impairment or quality of life .Our results show a better usability of the SSVEP-based BCI than the P 3 -based one for the sessions performed by the tested population of locked-in patients with respect to all the criteria considered . The study shows the advantage of developing alternative BCIs with respect to the traditional matrix-based P 3 speller using different designs and signal modalities such as SSVEPs to build a faster , more accurate , less mentally demanding and more satisfying BCI by testing both types of BCIs on a convenience sample of LIS patients .