title: Initial test of a T9-like P300-based speller by an ALS patient.
abstract: OBJECTIVE
  Visual P300-based brain-computer interface spellers offer a useful communication channel for locked-in patients, who are completely dependent in their daily lives. One of the research goals for these systems is to achieve greater communication rates by means of modifying some features of their interfaces, e.g., reducing the matrix size. However, such modifications may not work well with disabled end-users, such as patients of amyotrophic lateral sclerosis (ALS), due to a supposed reduction of their cognitive resources. The purpose of the present study was to provide a proof of concept that ALS patients could efficiently use a P300-based speller with a 4 × 3 symbol matrix based on the T9 interface developed for mobile phones.
  
  
  METHODS
  We conducted an experiment with a sample of 11 able-bodied participants and one locked-in patient with ALS. All participants tested our T9-like visual P300-based speller and also two different 7 × 6 matrix spellers based on Farwell and Donchin's classic proposal-one of them included a word predictor system like the T9-like speller did.
  
  
  RESULTS
  The performance analyses indicated that the locked-in patient benefited from using a reduced matrix size as much as healthy users did, spelling words almost 1.6 times faster and equally accurately when using the T9-like speller than when using the alternative spellers.
  
  
  CONCLUSIONS
  Due to counting on only one locked-in patient, the current work constitutes a feasibility study. The actual usability of systems such as the one proposed in this paper should be determined by means of studies with a greater number of end-users in real-life conditions.
authors.affiliation: Departamento de Tecnología Electrónica, Universidad de Málaga, Campus Teatinos, E-29071 Málaga, Spain.
authors.forename: R
authors.initials: R
authors.lastname: Ron-Angevin
authors.forename: S
authors.initials: S
authors.lastname: Varona-Moya
authors.forename: L
authors.initials: L
authors.lastname: da Silva-Sauer
mesh_terms: D000328:Adult; D000465:Algorithms; D000690:Amyotrophic Lateral Sclerosis / Q000503:physiopathology* / Q000534:rehabilitation; D001931:Brain Mapping / Q000379:methods; D062207:Brain-Computer Interfaces; D003143:Communication Devices for People with Disabilities; D004569:Electroencephalography / Q000379:methods*; D018913:Event-Related Potentials, P300; D005260:Female; D006801:Humans; D007802:Language; D008297:Male; D010865:Pilot Projects; D011597:Psychomotor Performance; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014796:Visual Perception; D015443:Word Processing / Q000379:methods; D055815:Young Adult