P300 based BCI messenger

A brain-computer interface (BCI) is a communication system that helps locked-in patients to communicate with other people by translating brain activities into machine/computer commands. This paper introduces a BCI instant messaging system (i.e. BCI messenger), which is further work of the P300-based Chinese typewriter developed in the preceding research. The BCI messenger can serve as a daily communication tool, with which the patients can type and send messages to either computer clients or cell phones. The typewriter interface is implemented following the design of modern cell phone keypad, where every key can act as a specific element in different input modes and multiple input modes including Chinese, English, numbers and symbols are integrated. Since P300 potentials exhibit various amplitudes and latencies on different individuals, some intensification parameters (e.g. variable stimulus round, inter-stimulus interval), and even some advanced intensification methods (e.g. stimulus size enhancement) could be customized to reinforce the elicitation of P300. Six subjects participated in the experiments of the BCI system above. A short training period is requested to allow task completion, and after about one hour´s practice, most of the subjects learned to operate the typewriter. All participators showed a gradual performance increase across sessions and average accuracy in the best condition for each subject surpassed 80%. Besides, effect of different electrode configurations and machine learning algorithms on classification accuracy is tested. The experiment results demonstrate that BCIs can provide locked-in patients with effective communication.