Oddball science helps locked in people communicate via a brain computer interface

Tampa 08 August 2005University of South Florida (USF) psychologist Emanuel Donchin and his students are perfecting ways to help people who are paralyzed yet fully conscious, with intact cognitive systems, communicate via a brain computer interface (BCI). Although the patient is unable to communicate, the electrical activity in their brains is normal. Through the BCI it becomes possible for users to "type" on a "virtual keyboard" using their brain waves.

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The BCI, according to Emanuel Donchin, can help patients who suffer from amyotrophic lateral sclerosis (ALS, or Lou Gehrig's disease) - a rare progressive neurological disorder that ultimately leads to a complete paralysis of voluntary muscles in all parts of the body; cerebral palsy; or patients "locked in" following a brain stem stroke.

"In essence, we are trying to provide the brain with new channels for communication and control by capturing and analysing the electrical or electro-encephalographic (EEG) activity produced in the brain", he explained. "Our goal is to restore communication functions."

To create an assistive "mental prosthesis", Emanuel Donchin's extensive work is focused on capturing and reporting unique brain activity that occurs upon the visual observation of a rare or "oddball" event. According to Emanuel Donchin, the "oddball paradigm" relies on a response to deviant stimuli embedded in a series of standard stimuli, such as letters, symbols and commands flashing randomly on a keyboard-like screen. By analysing the electrical activity as event-related brain potential (ERP) generated by the oddball event, the user in Emanuel Donchin's studies focuses attention on the character to be communicated as elements of the display are flashed on the screen.

"The chosen character is the one eliciting a P300", stated Emanuel Donchin. "Thus, by detecting which rows and columns in the display elicit a P300 the computer can determine the character the patient is trying to type."

In collaboration with the Wadsworth Institute at SUNY-Albany, Emanuel Donchin's group has conducted numerous studies with healthy and disabled volunteers who, wearing electrodes on their scalp attaching them to the BCI, were placed in front of an electronic screen display of 26 letters of the alphabet and other symbols and commands in a six-by-six row and columns flashing in random sequence. Test subjects were able to "operate" a virtual keyboard when their EEG reactions to oddball events in the random flashing were analysed. Researchers found greater electrical response in the rarely presented, or oddball, stimuli and the spike in the subjects' EEG at time of the oddball event created a means of communication.

"Ideally, the subject can spell out a message by successively choosing among the 26 letters", explained Emanuel Donchin. "We are examining the operating characteristics of this communication channel and analysing the speed with which there was an EEG focus on the letter of interest."

Test subjects were able to communicate their choice of a letter at the rate of about one character every 26 seconds. "This is, of course, a slow rate of communication", stated Emanuel Donchin. "But, considering there is no other channel of communication, even this slow rate is welcome."

Since coming to USF, Emanuel Donchin with his student Eric Sellers tested more than 15 ALS patients and have established that, in general, the system works although many adjustments in the procedure are required to allow the use of the BCI in patients' homes.


Leslie Versweyveld

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