Comparison of a row-column speller vs. a novel lateral single-character speller: Assessment of BCI for severe motor disabled patients Gabriel Pires a,b,⇑ , Urbano Nunes a , Miguel Castelo-Branco c a Institute for Systems and Robotics (ISR), University of Coimbra, 3030-290 Coimbra, Portugal b Department of Electrical Engineering, Polytechnic Institute of Tomar, 2300-313 Tomar, Portugal c Biomedical Institute for Research in Light and Image (IBILI), University of Coimbra, 3000-548 Coimbra, Portugal article info Article history: Accepted 19 October 2011 Available online 13 January 2012 Keywords: Brain–computer interface Electroencephalography P300 Event related potential Visual-paradigm Rehabilitation highlights  We propose a novel P300-based lateral single-character (LSC) speller, that explores layout, event strat- egy, and hemispheric asymmetries in visual perception to improve the performance of brain–computer interfaces.  The online performance of the LSC paradigm is compared to that of the standard row-column (RC) par- adigm.  The paradigms are tested by individuals with neuromuscular disorders (amyotrophic lateral sclerosis, cerebral palsy, Duchenne muscular dystrophy, and spinal cord injury). abstract Objective: Non-invasive brain–computer interface (BCI) based on electroencephalography (EEG) offers a new communication channel for people suffering from severe motor disorders. This paper presents a novel P300-based speller called lateral single-character (LSC). The LSC performance is compared to that of the standard row-column (RC) speller. Methods: We developed LSC, a single-character paradigm comprising all letters of the alphabet following an event strategy that significantly reduces the time for symbol selection, and explores the intrinsic hemispheric asymmetries in visual perception to improve the performance of the BCI. RC and LSC para- digms were tested by 10 able-bodied participants, seven participants with amyotrophic lateral sclerosis (ALS), five participants with cerebral palsy (CP), one participant with Duchenne muscular dystrophy (DMD), and one participant with spinal cord injury (SCI). Results: The averaged results, taking into account all participants who were able to control the BCI online, were significantly higher for LSC, 26.11 bit/min and 89.90% accuracy, than for RC, 21.91 bit/min and 88.36% accuracy. The two paradigms produced different waveforms and the signal-to-noise ratio was sig- nificantly higher for LSC. Finally, the novel LSC also showed new discriminative features. Conclusions: The results suggest that LSC is an effective alternative to RC, and that LSC still has a margin for potential improvement in bit rate and accuracy. Significance: The high bit rates and accuracy of LSC are a step forward for the effective use of BCI in clin- ical applications. Ó 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. 1. Introduction Brain computer interfaces (BCIs) can offer new communication opportunities to individuals with severe motor disabilities (Wolpaw et al., 2002). Potential BCI users are individuals suffering from severe motor disabilities by disorders such as amyotrophic lateral sclerosis (ALS), progressive muscular dystrophy, cerebral palsy (CP) and spinal cord injuries (SCI) (Mak and Wolpaw, 2009). BCI can also represent an alternative to other interfaces for individuals who still retain a weak ability to control some part of the body, but whose motor performance is very low and show difficulty in controlling some standard interfaces. Increasing the communication abilities of these individuals by improving the accessibility to computers and means of locomotion such as wheelchairs, provides a higher level of independence and self- satisfaction, thus enhancing their quality of life. 1388-2457/$36.00 Ó 2011 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.clinph.2011.10.040 ⇑ Corresponding author at: Institute for Systems and Robotics (ISR), University of Coimbra, 3030-290 Coimbra, Portugal. Tel.: +351 962782654. E-mail address: gpires@isr.uc.pt (G. Pires). Clinical Neurophysiology 123 (2012) 1168–1181 Contents lists available at SciVerse ScienceDirect Clinical Neurophysiology journal homepage: www.elsevier.com/locate/clinph