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Digital Signal Processing of Spatio-Temporal Electroencephalogram (EEG) Patterns Associated With Voluntary Motion Preparation

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Digital Signal Processing of Spatio-Temporal Electroencephalogram (EEG) Patterns Associated With Voluntary Motion Preparation  

Electrode Placement:

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Recording

The following charts were obtained from an off-line analysis of a recording session in which the subject was asked to produce and suppress the Mu rhythm in 30 Sec time intervals.  The first 30 Sec time interval of each file, the subject was asked to produce the Mu rhythm.  The Electroencephalogram signals were amplified and digitized at a sampling frequency of 500 samples/sec.  The off-line analysis was performed using the MATLAB software.
 

Off-line analysis

Frequency analysis on the Electroencephalogram signals was  performed using two Goertzel algorithms.  The two frequencies investigated using the Goertzel algorithms were 6 Hz and 12 Hz.  The Goertzel algorithm provides a meaning result after N samples of the signal being studied have been processed. In our experiments we chose N = 500 such that within a given 30 Sec time interval,  a total of 24 windows can be taken.  Therefore, within a 30 Sec interval in which the subject was asked to produce the Mu rhythm, there should be 24 Mu rhythm detections.  A Mu rhythm detection was determined when the following was true: (Power in 12 Hz band)/( Power in 6 Hz band) > 1.
 

Interpreting the charts

The blue bars corresponds to Mu rhythm detections made by the algorithm which implemented the two Goertzel algorithms.  The purple bars corresponds to Mu rhythm collapse detections made by the algorithm.  Therefore, in the 30 Sec time intervals in which the subject was asked to produce the Mu rhythm, there should be a total of 24 Mu rhythm detections (i.e., blue bar -> 24 and purple bar -> 0).  Similarly, in the 30 Sec time intervals in which the subject was asked to suppress the Mu rhythm, there should 24 Mu rhythm collapse detections (i.e., purple bar -> 24 and blue bar -> 0).

In the charts below, the first window corresponds to the subject being asked to produce the Mu rhythm, the second window to the subject asked to suppress the Mu rhythm, the third to the subject being asked to produce the Mu rhythm, and so forth in an alternating fashion (i.e., Mu, No Mu, Mu, No Mu, etc.).
 
 

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The frequency analysis done on the EEG signals focused on monitoring two frequency bands: 6 Hz and 12 Hz.  The ratio between the frequency bands indicates the amount of "Mu power" in the signal.
 
 

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Hypothesis

Modules

Preliminary Results: Mu detection

Preliminary Results: Readiness Potentials Classification