Fig. 3From: Boosting brain–computer interfaces with functional electrical stimulation: potential applications in people with locked-in syndromeIllustration of the facial muscles. The facial muscles that have been stimulated in previous facial FES studies are highlighted in red: the frontalis (forehead), orbicularis oculi (eye), zygomaticus major (cheek), masseter (cheek), and orbicularis oris (mouth). Adapted from [309], copyright by the authorsBack to article page