Figure 1.

From left to right, example visual displays for the following BCIs: P300 grid speller, RSVP P300, SSVEP, and motor-based (SMR with keyboard). For the P300 grid, each row and column are highlighted until a letter is selected. In the RSVP, each letter is displayed randomly, sequentially in the center of the screen. For the SSVEP, this example uses four flickering stimuli (at different frequencies) to represent the cardinal directions, which are used to select individual grid items. This can also be done with individual flicker frequencies for all 36 items with certain technical considerations. For the motor-based BCI, this is an example of a binary-selection virtual keyboard; imagined right hand movements select the right set of letters. RSVP = rapid serial visual presentation; SSVEP = steady state visually evoked potential; SMR = sensorimotor rhythm; BCI = brain–computer interfaces. Copyright © Tobii Dynavox. Reprinted with permission.