Table 3.

Comparison of spelling performance between this study and other spelling BCI studies

	Able-Bodied Participants		Participants with ALS Without LIS		Participants with LIS
Speller type	Switch	P300/SSVEP	Switch	P300/SSVEP	Switch	P300/SSVEP
Scalp EEG	0–0.86* (Bai et al. 2010)	2.6 (McCane et al. 2015);	0 (Hill et al. 2006);	<2.1 (Nijboer et al. 2008);	0.5 (Birbaumer et al. 1999);	2.1 (McCane et al. 2014);
		5.48 (Pires et al. 2012);		4.97 (Pires et al. 2012);
		5.83 (Chen et al. 2015)	1.2* (Miner et al. 1998)	1.16 (Mainsah et al. 2015)	<2 (Kübler et al. 2001)	<1 (Sellers et al. 2014)
ECoG	0.51 (Hinterberger et al. 2005)	17 (Brunner et al. 2011)			0 (Hill et al. 2006);	0 (Murguialday et al. 2011)
					1.82 (Vansteensel et al. 2016)
Intracortical LFP-based (this study)			6.88		3.07
Intracortical spike-based using other speller types			10.44–17.40 (Jarosiewicz et al. 2015);		9.4 (Bacher et al. 2015);
			13.5–31.6 (Pandarinath et al. 2017)		1.95–11.75 (Jarosiewicz et al. 2015)

Bold values represent the present study. Other studies include all studies listed in three recent reviews (Fazel-Rezai et al. 2012; Kübler and Birbaumer 2008; Marchetti and Priftis 2015). Performance of BCI-based spellers in able-bodied people, people with ALS who retain the ability to speak, and people with LIS resulting from ALS or stroke, as measured in correct characters per minute. When only selections per minute were reported, we include this value as an upper bound. When only binary selections were allowed we estimated a typing rate based on a simple switch keyboard design, with five selections required per character (marked with *). ALS, amyotrophic lateral sclerosis; BCI, brain-computer interface; ECoG, electrocorticographic signals; LIS, locked-in syndrome; LFP, local field potential; SSVEP, steady state visually evoked potential.