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EEG-based Computer Interface

The goal of this project is to develop an EEG-based computer interface which can be used by profoundly paralysed patients to control a communication device. There exists a significant population who, due to disease or injury, are totally paralysed but have normal or near-normal brain function. In such cases, called Locked-in-Syndrome, the patient is aware of his or her surroundings, but has no way of communicating with the outside world. This project will explore how brain-waves recorded from scalp electrodes can be used as a switching device to control a computerized communication system. We have decided to use an evoked potential known as P300 as the switch in our system. P300 is a well-studied, easily reproducible brain signal that occurs in response to a significant but low-probability event. This signal is typically elicited using an "oddball paradigm" in which the subject detects occasional low-probability target stimuli randomly interspersed among more frequently presented background stimuli. The P300 is a positive wave that occurs about 300 milliseconds after the onset of the target (oddball) stimulus. The proposed research will explore the utility of presenting two or more simultaneous oddball tasks to the subject while recording his or her EEG. The tasks will appear in different positions on a computer monitor. Each task will present targets at different times. By hypothesis, P300s will be produced only for the targets in the oddball task that the subject is attending to, and not for the targets from other tasks that are running in other locations on the screen. The experimenter should be able to tell which screen location the subject is attending to by matching P300 acquisition times with target presentation times for each task. Depending on the number of tasks running in different locations on the screen, each location can represent anything from simple yes-no decisions to letters of the alphabet.

Polikoff, J., Bunnell, H.T., and Borkowski, W. (1995). "Toward a P300-based Computer Interface." Proceedings of the RESNA '95 Annual Conference, RESNAPRESS, Arlington Va. pp 178-180. html ps pdf

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