Fig. 3.

Imagination protocol. The user imagines speaking a word when an auditory cue in the form of a beep is presented. One second after each cue are used for the first experiment, and 312 ms for the second. A random rest period of 3–7 s occurs between trials. This sufficiently separated the tasks from one another. Also, the random duration prevents the user from anticipating the task onset based on rhythm. As a result, the next stages of linguistic functions begin exactly after cue recognition and the system is perfectly synchronised