offline analysis of Mu

Forum for discussion on different signal processing algorithms
Locked
emily
Posts: 40
Joined: 24 Mar 2008, 06:13

offline analysis of Mu

Post by emily » 07 Apr 2008, 21:53

Hi,
We're going through the offline analysis tutorial and wanted to check that the practice files are actually Mu files not P300 or something else.

As the files seem to have picked out 19Hz and 31Hz for online classification, with high correlations between rest and foot movement rather than at 8-12hz where we expected low correlations ie. large differences between rest and foot movement.

If they are Mu files could you please explain why they use such high frequencies.

thanks,

josh
Posts: 14
Joined: 07 Apr 2008, 19:52

Post by josh » 07 Apr 2008, 22:30

Hi Emily,
If you could list the files to which you're referring I'll do my best to provide an answer.

- Josh

emily
Posts: 40
Joined: 24 Mar 2008, 06:13

Post by emily » 07 Apr 2008, 23:59

Hi Josh,

The files are eeg1_1.dat, eeg1_2.dat and eeg1_3.dat
and the tutorial I'm running through is on this page http://www.bci2000.org/wiki/index.php/U ... f_EEG_Data

thanks

josh
Posts: 14
Joined: 07 Apr 2008, 19:52

Post by josh » 08 Apr 2008, 15:31

Hi Emily,
Sorry for the delay. As you noted, the Mu band is typically accepted to be a ~3Hz band centered at around 12Hz. Another band typically used in EEG-based BCI is the beta band which is considered to be centered at around 24Hz. Very often you will see similar changes in activity for both of these bands. For example, when a subject is asked to more his/her right hand, we expect a bilateral response over the motor cortex but with a stronger response on the contralateral (i.e., left in this case) motor cortex. This is true for Mu frequencies. Beta frequencies, however, tend to be centered at the vertex of the head (see McFarland 2000 - Mu and Beta Rhythm Topographies During Motor Imagery and Actual Movements). Now, all that said, each person will have a unique response to any given stimulus, but we should typically be able to find some similarities. In the case of the analysis you referred to, we find that desynchronization occurs most notably at ~19Hz and ~31Hz. Notice that the latter is a near multiple of the former as in the case of Mu and Beta frequencies. Also notice that the corresponding topographies are bilateral and centered respectively and each over the motor cortex. So, it seems reasonable to conclude, given the evidence in conjunction with previous research, that these features are not artifacts and are likely correlated to the related movement. Hope this helps. Good luck on your research.

- Josh

faisal1
Posts: 12
Joined: 16 Jun 2008, 16:57

Post by faisal1 » 21 Jun 2008, 00:47

hi josh'

Could u answer my these confusions??

1) As we know that during the right hand movement / imagination , the dominent part of brain is Left Hemisphere. Please tell me, during this hand movement , what is the Effect on Right Hemisphere ( the power of mu Signal Decreases or INcrease )???

2) what conditions follows by subject ( saved the BCI2000), imean to say eeg1_2.dat ?? Was the data extracted during right or left hand/foot movements..


Regards
Faisal

Locked

Who is online

Users browsing this forum: No registered users and 3 guests