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.
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This document was last updated April 7, 1998
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