Abstract
Brain-computer interface (BCI) spellers allow severe motor-disabled patients to communicate using their brain activity without muscular mobility. Different visual configurations of the widely studied P300-based BCI speller had been assessed with healthy and motor-disabled users. However, the speller size (in terms of cm) had only been assessed for healthy subjects. We think that the speller size might be limiting for some severely motor-disabled patients with restricted head and eye movements. The usability of three speller sizes was assessed for seven patients diagnosed with amyotrophic lateral sclerosis (ALS) and a participant diagnosed with Duchenne muscular dystrophy (DMD). This is the first usability evaluation of speller size with severely motor-disabled participants. Effectiveness (in the online results) and efficiency (in the workload test) of the medium speller was remarkably better. Satisfaction was significantly the highest with the medium size speller and the lowest with the small size. These results correlate with previously described findings in healthy subjects. In conclusion, the speller size should be considered when designing a speller paradigm, especially for motor-disabled individuals, since it might affect their performance and user experience while controlling a BCI speller.
Highlights
Amyotrophic lateral sclerosis (ALS) is a neurological disorder that degenerates the upper and lower motor neurons, leading to paralysis and eventually death (Patterson and Grabois, 1986)
The collected results from the patients are presented according to the usability criteria
Classification Accuracy During the Calibration Phase According to Friedman’s tests, no significant differences in accuracy between sizes were found in any sequence (Figure 2)
Summary
Amyotrophic lateral sclerosis (ALS) is a neurological disorder that degenerates the upper and lower motor neurons, leading to paralysis and eventually death (Patterson and Grabois, 1986). Other functions such as sensory perception or intellectual abilities are usually preserved. Duchenne muscular dystrophy (DMD) is a genetic progressive muscular degeneration disorder which leads to paralysis and eventually death (Emery et al, 2015). As with ALS patients, DMD patients usually preserve their sensory perception and intellectual abilities (Emery et al, 2015). Some of the main differences between ALS and DMD disorders are that DMD is genetic, usually starts at early ages—childhood—and often evolves slowly; while ALS cause is unknown, usually starts at later ages—adulthood—and normally evolves faster than DMD
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