Fractal dimension-based EEG biofeedback system

Biofeedback plays an increasingly important role in mainstream computer applications, including hands-free human-machine interaction. The most obvious use of this technology is to help disabled people interact with their environment. The main challenge in brain computer interfaces is to identify the particular EEG signal components that can be successfully used as control commands. In this study, we show that the fractal dimension of EEG is such a component. This is verified via the experiments carried. The fractal dimension is known to be a good measure of the chaotic behavior of the EEG signal. An algorithm proposed by Higuchi is used to estimate the fractal dimension. Visual and auditory information extracted from the EEG signal of each subject are fed back to himself. Each subject was asked to perform any mental activity so as to alter the value of his EEC´s fractal dimension. Our experiments show the feasibility of the EEG biofeedback method to change the fractal dimension of the EEG signal. Our study introduces the fractal dimension as a new feature that can be controlled by a person and used in brain computer interface systems.