Is it possible and feasible to use the LORETA images from a passive task EEG experiment to visualize the frontal alpha asymmetry (FAA) from some participants?
To be more precise I include some details below:
1. I have 60s. long segments, and the LORETA images can be directly displayed in the software I use, after selection of entire segment (before the FTT transform; an example attached).
2. Is there a way to interpret the LORETA image in relationship to the power bands? In my case I want to show the frontal alpha asymmetry , which is characterized by greater brain activation on the left compared to the right frontal hemisphere (or in other words, increased alpha power on the right).
3. Is it common to edit the LORETA image in the graphical software to, for example add on the electrode placement, or mark out one specific region of interest?
4. In the preliminary study I have 22 participants, and I would like to use LORETA images as an interesting and engaging way to visualize my outcomes. Should I incorporate images from all participants for each of the 3 conditions, or it is ok to just present some selected extreme cases?
Thank you for your advice!!
I would recommend you using sLORETA software (Pascual-Marqui, 2002) for any EEG source analysis. It allows to locate sources corresponding to specific EEG bands (alpha, etc.), and also ERPs.
More importantly, I would recommend tofind statistical differences (t-test) in brain source activation between conditions (ERPs or oscillations) in your sample. The analysis outcome is the location of those brain areas that surpass statistic criterion (95%).
For a tutorial of the whole process, please find the sLORETA help file.
Thank you Mr. Muñoz. How can you explain in Loreta t.tests "when" and "where" brain maps show yellow (+) and purple (-) activity for a LPC effect.
I guess it should only reflect yellow positive activity...
Thanks :)
Dear Mr. José Sanchez, when comparing two conditions (A, B) in sLORETA, t-test yields positive and/or negative t values to each time-point or time-window depending the contrast A>B or B>A. I understand that "When" question is related at the time-window around your LPC effect. "Where" question at this time-window is asked by a voxel 3-D map showing warm (significant) voxels testing A>B and cold voxels testing B>A. I hope you find this helpful :)
- Badges
- Science topic