Table 1.

Summary of BCI varieties and their feedback modality.

EEG signal type	Sensory/Motor modality	User requirements
Event-related potentials	Visual P300 (grid)	Visual oddball paradigm, requires selective attention around the screen
	Visual P300 (RSVP)	Visual oddball paradigm, requires selective attention to the center of the screen only (poor oculomotor control)
	Auditory P300	Auditory oddball paradigm, requires selective auditory attention, no vision requirement
Steady state evoked potentials	Steady state visually evoked potential	Attention to frequency tagged visual stimuli, may increase seizure risk
	Auditory steady state response	Attention to frequency modulated audio stimuli
Motor-based	Continuous sensorimotor rhythm	Continuous, smooth control of interface (e.g., cursors) using motor imagery (first person)
	Discrete event-related desynchronization	Binary (or multichoice) selection of interface items (# choices = # of imagined movements), requires motor imagery ability
	Motor preparatory signals, for example, contingent negative variation	Binary selection of communication interface items using imagined movements
Operant conditioning	Slow cortical potentials	Binary selection of communication interface items after biofeedback-based learning protocol

Note. BCI = brain–computer interface; EEG = electroencephalography; RSVP = rapid serial visual presentation.