Nowadays, brain-computer interfaces (BCIs) are being extensively explored by researchers to recover the abilities of motor-impaired individuals and improve their communication. Text entry is one of the most important regular tasks in communication, and BCI has high application potential to develop a speller. Although BCI has been a growing research topic for the last decade, more progress is yet to be made for BCI-based spellers. Two challenges are there in BCI speller development: designing an effective graphical user interface with an optimal arrangement of symbols enabling a minimum number of control commands and reducing usersā efforts in error correction following an efficient error-correction policy. With this scope in mind, this work proposes a novel BCI speller paradigm with an efficient symbol arrangement to improve the text entry rate. Additionally, it provides a user-friendly error correction approach through six text-cursor navigation keys to enhance the accuracy of text entry. The proposed speller includes 36 target symbols and is operated with two control commands obtained from electroencephalogram motor-imagery signals. The experimental results revealed that the proposed speller outperforms the existing motor imagery-based BCI spellers when tested on ten motor-impaired users. This speller achieved a mean performance of 5.20 characters per minute without any typing error and 6.04 characters per minute with a 2.9 percent mean error. The mean correction efficiency was 0.69; that is, users corrected 69 percent of incorrect inputs with a single correction key pressed.
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