Using other electrodes as reference


#1

Hi,
I need you help to better understand how Muse uses the reference electrodes. I am questioning your choice of the using 3 frontal electrodes as the reference/DRL. Usually when doing EEG, the reference electrodes used are placed on the mastoid process, just being the ear. By using frontal electrodes, I suspect that the signal in the Fp1 and Fp2 electrodes will be much flatter, since the reference electrodes are just a few cm beside. I have tested this my measuring alpha waves during meditation… Using other EEGs, I would get increased Alpha wave amplitude in the prefrontal cortex (Fp1 and Fp2), but I cannot see this increase with Muse.
I would like to use TP9 and TP10 as reference electrodes instead of the frontal ones. According to this thread (http://forum.choosemuse.com/forum/developer-forum/4361-how-to-use-drl-ref-data), all I need to do is to subtract TP9 (or TP10) from the other channels. I have tried to do that but the results were not convincing… It would be easier if one had a better picture of the internal circuit and digital signal processing of muse. I understand that most of this information is proprietary but any help would be greatly appreciated on how to use the TP9/TP10 electrodes as references. Thanks!


#2

Hi ZigZagZen7,

Take a look at the NeuroMore Studio tool suggested in this post:
http://forum.choosemuse.com/forum/developer-forum/9660-neuromore-studio-visualization-tool-and-signal-processing-engine

Maybe it can help you achieve what you want to do.
The picture bellow show what I tried to do, by using the average of TP9 and TP10 as reference to FP1 and FP2 and then doing a TFT and Band Filter to get only Alpha.
(As I’ve said, I know nothing about DSP and the field, so my design maybe totally wrong - I used only some logic. But if you know the field you will know the correct way to do it).

(click on the image to see it in full size)