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Mu Rhythm Variability and its Impact on the Development of Brain-Computer Interfaces

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"Mu Rhythm Variability and its Impact on the Development of Brain-Computer Interfaces", (1999)
Barreto, A. B. , Annette Taberner and Malek Adjouadi

ABSTRACT: Several research groups are currently pursuing the development of a Brain-Computer Interface (BCI). Using these interfaces disabled individuals could control their computers through voluntary changes in their Electroencephalogram (EEG). A number of proposed BCI approaches depend on the detection of the "Mu (m) Rhythm". This 8-13 Hz rhythm is believed to dominate the motor cortex of a subject at rest. However, references in the literature and our own observations indicate that the strength of the Mu Rhythm oscillations varies with time, even when the subject remains at rest. This paper investigates the effect of those variations on the speed at which a Mu-based BCI can reliably operate. An analysis of the EEG recorded over the motor cortex of six college-aged subjects is performed, and results are provided. The signal power in the Mu-Rhythm band (8-13 Hz) was computed using the Discrete Fourier Transform (DFT) within varying observation time windows. The effect of the different window lengths on the efficiency of the system in determining the presence or absence of the Mu Rhythm using a threshold was investigated. The results obtained indicate that a DFT observation window of at least 1.5 seconds is needed, since it encompasses several cycles of the Mu rhythm variations, thus improving the reliability of the Mu Rhythm detector.