A Virtual Keypad Based on Alternate Half-Field Stimulated Visual Evoked Potentials

A virtual 8-key keypad has been designed and constructed to experimentally validate a new kind of noninvasive brain computer interface (BCI). The principle of its operation is based on a technique of alternate visual half-field stimulation, proposed recently by second of the authors. Microcontroller and DSP integrated circuits are used to generate the signals driving light-emitting diodes for visual stimulation and to detect brain response in the EEG signal. The EEG signal is measured from 3 electrodes placed on occipital part of the scalp using a battery- operated amplifier and A/C converter. A Bluetooth chip is used to transmit the stream of measured data to the processor. Tests of the keypad operation, involving 10 volunteers, show it is faster than conventional BCI devices based on steady-state visual evoked potentials, reported so far in the literature.