Capability to temporally filter stimuli predicts P300-based brain-computer interface performance in people with amyotrophic lateral sclerosis

Objectives: A Brain computer interface (BCI) exploits the userâEUR(TM)s neurophysiological signals to realize interaction with the environment (Wolpaw and Wolpaw, 2012). People with amyotrophic lateral sclerosis (ALS) are considered potential users of BCIs, since severe motor impairment at late stages of the disease prevent any form of conventional communication. Nevertheless, the influence of their cognitive capabilities on the ability to control a P300-based BCI (P300-BCI) have not been fully investigated. The purpose of this study was to investigate the influence of attentional and memory processes of people with ALS on the performance in a P300-based speller task and on the amplitude of the P300 event related potential (ERP).
Materials: Nine people with ALS (3 women; mean age=59.7±12.3; mean ALSFRS scores: 32.4± 8.2; Brooks et al., 1996) were included in the study.
Methods: Participants were asked to perform i) a rapid serial visual presentation (RSVP) task, screening the temporal filtering capacity and the speed of the update of the attentive filter ii) a change detection (CD) task, screening the memory capacity and the attentional spatial filtering capacity iii) a P300-BCI spelling task (Farwell and Donchin, 1988). Scalp electroencephalographic (EEG) signals during the P300-BCI task were recorded from 8 channels (Fz, Cz, Pz, Oz, P3, P4, PO7 and PO8). We performed a correlation between the variables related to the RSVP and CD tasks, the performance and the amplitude of the P300 elicited in the BCI task. Regression analyses were performed for the parameters whose correlation was statistically significant. Results: We found that the temporal filtering capacity in the RSVP task was a predictor of both the performance (p<0.05 with β=0.079) and the amplitude of the P300 elicited performing the BCI task (p<0.05 with β=0.087).
Discussion: Following the Huang and PashlerâEUR(TM)s (2007) Boolean Map Theory of visual attention, the attentional filter is achieved by a boolean map, a mechanism of visual access (spatial filter) that divides the visual field into selected and unselected subfields. A top down mechanism creates and maintains over time the Boolean maps. We speculate that such top-down mechanism is crucial to control a BCI speller task, allowing the user to set up and maintain the proper attentional map throughout a trial and thus to select the desired letter.
Conclusion: The ability to keep the attentional filter active during the selection of a target influences performance in BCI control in people with ALS.