In Search of the Mu Rhythm
Hello! We are inching towards our goal of giving you a superpower! Last time, I was trying to find the mu rhythms, and I strongly think I may have found them. This consisted of two main steps. One was to find the right montage (electrode locations) which will help us see the mu rhythms. And once I figured the locations, the next step was to hunt for those distinct mu rhythms. For this I needed, a suitable data recording protocol. Both of which I didn’t seem to settle upon quickly. After multiple unsuccessful tests on my mentor who also agreed to be my subject, there was a tiny ray of hope.
I decided upon using 4 channels corresponding to 4 locations on the scalp.
Here’s an image of the international 10/20 system used to specify the electrode locations.
One of them is keeping the positive lead on F4 and negative(reference) on C4 with the ground lead on the mastoid (the bone behind the ear), or the positive lead on C4 and negative(reference) on Fz. And ofcourse, to maintain symmetry, there are two channels on F3/C3 and C3/Fz. As we know, the left hemisphere of the brain corresponds to the right part of our body and vice versa.
And now, time for some data blitz! Hello, mu rhythms!
The waves after the breakpoint correspond to when there was movement. There is a stark difference between the nature of waves before and after movement. There is a desynchronisation of the EEG waves right when a movement is happening. This is nothing but the mu-wave suppression which I mentioned in my last post.
However, just a visual observation of these mu waves is not enough. To accomplish our end goal, we need better visualisation; a way to quantify this suppression. And that’s what I am working on presently. One way to do this would be to calculate the power corresponding to each frequency and plot it. Theoretically, there should be a reduction of power in the 8-14 Hz band every time there is a movement. Or every time there is an imagined movement. The power plots gave me promising leads. Here’s a snippet of the power spectral density.
This is a plot with the data collected from F4-C4, the location that corresponds to left hand. As we can see, the waves for relaxed state, and right hand movement (both imagined and actual movement) have equivalent power. However for the left hand movement there is a significant decrease in power. And a slightly less reduction in power for imagined left hand movement. This corresponds with our expectations.
Currently, I am in search of more features and processing techniques that I can use in order to train a model to predict imagined movements. Simultaneously, collecting as much as data as possible. One can never have too much data!
Apart from work, my last two weekends were quite interesting. One of them I hosted my sister’s classical indian dance show and the other weekend I visited the picturesque Michigan’s Little Bavaria: Frankenmuth!
The shockingly unpredictable World Cup has kept me occupied too!
I look forward to updating all of you with hopefully some more good results! But until then, Auf Wiedersehen!