Introducing the tactile speller: an ERP-based brain–computer interface for communication

Abstract

In this study, a tactile speller was developed and compared with existing visual speller paradigms in terms of classification performance and elicited event-related potentials (ERPs). The fingertips of healthy participants were stimulated with short mechanical taps while electroencephalographic activity was measured. The letters of the alphabet were allocated to different fingers and subjects could select one of the fingers by silently counting the number of taps on that finger. The offline and online performance of the tactile speller was compared to the overt and covert attention visual matrix speller and the covert attention Hex-o-Spell speller. For the tactile speller, binary target versus non-target classification accuracy was 67% on average. Classification and decoding accuracies of the tactile speller were lower than the overt matrix speller, but higher than the covert matrix speller, and similar to Hex-o-Spell. The average maximum information transfer rate of the tactile speller was 7.8 bits min(-1) (1.51 char min(-1)), with the best subject reaching a bit-rate of 27 bits min(-1) (5.22 char min(-1)). An increased amplitude of the P300 ERP component was found in response to attended stimuli versus unattended stimuli in all speller types. In addition, the tactile and overt matrix spellers also used the N2 component for discriminating between targets and non-targets. Overall, this study shows that it is possible to use a tactile speller for communication. The tactile speller provides a useful alternative to the visual speller, especially for people whose eye gaze is impaired.

Operation of a P300-based brain-computer interface by patients with spinocerebellar ataxia

“…For example, several gaze-independent BCIs have been reported previously; visual BCIs, auditory BCIs, and tactile BCIs are three main categories (Riccio et al, 2012). A Hex-O speller, which needed covertly directed attention to a target, is a gaze-independent visual BCI (Treder and Blankertz, 2010, Marjolein van der et al, 2012). Severens et al showed that patients with moderate ALS could achieve high performance in a copy-spelling task with the Hex-O speller (Severens et al, 2014).…”

Multi-command Tactile Brain Computer Interface: A Feasibility Study

“…A recent report [12] proposed using a Braille stimulator with 100 ms static push stimuli delivered to each of six fingers to evoke a somatosensory response potential (SEP) related P300. The P300 response is a positive electroencephalogram event-related potential (ERP) deflection starting at around 300 ms and lasting for 200 − 300 ms after an expected stimulus in a random series of distractors (the so-called oddball EEG experimental paradigm) [7].…”

Multi–command Chest Tactile Brain Computer Interface for Small Vehicle Robot Navigation

“…The P300 responses are commonly used in BCI approaches and are considered to be the most reliable ERPs [16,21] with even beginner subjects. The results in [20] indicated that the experiments achieved information transfer rates of 7.8 bit/min on average and 27 bit/min for the best subject. A very recent report [7] additionally confirmed superiority of the tactile BCI (tBCI) in comparison with visual and auditory modalities tested with a locked-in syndrome (LIS) subject [14].…”

“…A more recent report [20] proposed using a Braille stimulator with 100 ms static push stimulus delivered to each of six fingers to evoke a somatosensory evoked potential (SEP) response and the following P300. The P300 response is a positive electroencephalogram event-related potential (ERP) deflection starting at around 300 ms and lasting for 200 − 300 ms after an expected stimulus in a random series of distractors (the so-called oddball EEG experimental paradigm) [13].…”