Mu Rhythm Linear Classifier Signal Questions

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ebjorklund
Posts: 8
Joined: 20 Jun 2019, 13:57

Mu Rhythm Linear Classifier Signal Questions

Post by ebjorklund » 18 May 2020, 15:52

Hello I have some questions regarding the mu rhythm linear classifier and ensure that we are using the correct control signals. For spatial filtering we simply use the CAR filter type. From this, we select C3 and C4 as outputs of the filter in the "SpatialFilterCAROutput" box. My question is in regards to the Linear Classifier matrix. It is our wish to use frequencies in the mu and beta band control a cursor to move horizontally. We wish to have motor imagery detected on C3 to move the cursor to the right, and have motor imagery detected on C4 to move the cursor to the left. In the input column, we have [1, 2, 1, 2] with "1" being spatially filtered signal from C3 and "2" being spatially filtered signal from C4. In the input element column we have [8Hz, 8Hz, 18Hz, 18Hz] to represent the mu and beta frequency values. In the output channel column we have [1, 1, 1, 1] as we only want horizontal movement. And then in the weights column we have [1, -1, 1, -1] with positive values associated with C3 intended to move the cursor to the right and negative values associated with C4 intending to move the cursor to the left. I have attached a screenshot as well.
Capture.PNG
Capture.PNG (5.58 KiB) Viewed 39 times
My main question involves the weights. Are these the correct weights to achieve the performance that we are looking for? A previous group had the weights as [-1, 1, 1, -1] however I believe this to be a mistake. Thank you.

mellinger
Posts: 1098
Joined: 12 Feb 2003, 11:06

Re: Mu Rhythm Linear Classifier Signal Questions

Post by mellinger » 21 May 2020, 07:53

Hi, I think the other group's values are correct rather than yours. "Detecting motor imagery" is equivalent to a reduction in SMR amplitude. C3 is on the left hemisphere, and linked to the right hand. You wish right hand motor imagery to move the cursor right, so a reduction at C3 should increase the value of the x coordinate. This means that C3 should have a negative weight, and C4 should have a positive weight in the classifier matrix.

HTH,
Jürgen

ebjorklund
Posts: 8
Joined: 20 Jun 2019, 13:57

Re: Mu Rhythm Linear Classifier Signal Questions

Post by ebjorklund » 21 May 2020, 11:37

Thank you very much for the reply. I realize now that the correct weighting is [-1 1 -1 1]. This would apply negative weighting to the Mu and Beta bins from C3 (Right hand movement) and positive weighting to the Mu and Beta bins from C4 (Left hand movement).

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