[Eeglablist] Separating out Alpha from mu oscillations

B L thirstyforknowledge123 at gmail.com
Tue Mar 25 14:40:50 PDT 2014

Hi Matthew(and others),

Thanks for your suggestions.
Just few clarifications. So I assume the CSD(& Hjorth transform) method you
are suggesting is to remove the effect of volume conduction, right?
And yes, I always baseline correct the data using pre-stim data(with no
movements) as baseline in time and frequency(while calculating ERSP)
So if I perform the above two steps, can I be sure that the effect of alpha
is very much minimized in the central region? In other words, can I simply
ignore the effect of alpha  when I compare central regions in the alpha
freq. band(7-13hz or 8-13hz) between 2 groups of interest?

Thanks again,

On Tue, Mar 25, 2014 at 2:47 PM, Chuck Telestel <sunshineafterdusk at gmail.com
> wrote:

> Hi,
> One way, not the only way, would be to use current source densities or
> apply a Hjorth transform to the data. The effect is that more global alpha
> rhythms won't mask your mu rhythms. Use the electrodes over the motor
> regions contra-lateral to movement (C3 & C4: 10/20 system).
> It also a good idea to have pre-movement data for a baseline correction.
> You could use time-domain and frequency domain representations. Your
> mu-desychronisation will be clearly visible in the upper alpha band
> (approx. 10-12hz). Bear in mind that the alpha band varies across
> individuals so not everyones upper alpha will neatly fall into this band.
> There are a couple of ways, but the above gives decent results. Good luck.
> Matthew
> On 25 Mar 2014, at 3:58 PM, B L <thirstyforknowledge123 at gmail.com> wrote:
> Hi,
> I guess this topic has been discussed in the past but I cant find an
> effective solution.
> We know that, it  is very common for the alpha oscillation to have
> influence up to almost the frontal electrodes. My question is - If we are
> interested only in mu rhythm in a visual-motor task, what is the best way
> to tease out the alpha activity from the motor regions so the comparison
> across groups is more effective?
> Will ICA work better for this(just identifying the alpha component and
> removing it)? Is there any other method researchers commonly use for this
> purpose?
> Any help is much appreciated.
> Thanks!
> Bala
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