Frontiers in Neuroscience (Jan 2012)
Switching between manual control and brain-computer interface using long term and short term quality measures
Abstract
Assistive devices for persons with limited motor control translateor amplify remaining functions to allow otherwise impossible actions.These assistive devices usually rely on just one type of input signalwhich can be derived from residual muscle functions or any other kindof biosignal. When only one signal is used, the functionality of theassistive device can be reduced as soon as the quality of the providedsignal is impaired. The quality can decrease in case of fatigue, lack ofconcentration, high noise, spasms, tremors, depending on the type ofsignal. To overcome this dependency on one input signal, a combination of more inputs should be feasible. This work presents a hybridBrain-Computer Interface (hBCI) approach where two different inputsignals (joystick and BCI) were monitored and only one of them waschosen as a control signal at a time. Users could move a car in agame-like feedback application to collect coins and avoid obstacles viaeither joystick or BCI control. Both control types were constantlymonitored with four different long term quality measures to evaluate the current state of the signals. As soon as the quality droppedbelow a certain threshold, a monitoring system would switch to theother control mode and vice versa. Additionally, short term qualitymeasures were applied to check for strong artifacts that could rendervoluntary control impossible. These measures were used to prohibitactions carried out during times when highly uncertain signals wererecorded. The switching possibility allowed more functionality for theusers. Moving the car was still possible even after one control modewas not working any more. The proposed system serves as a basisthat shows how BCI can be used as an assistive device, especially incombination with other assistive technology.
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