Using EEGlab it is possible to display channel spectra and maps that plot EEG power with frequency. However, I am unsure how to obtain the data making up these plots so I can calculate the mean power across specific frequency bands (i.e. 4-8Hz for theta).
For example, in a relative paper, the researchers state:
"EEG power was computed on the electrode of interest (see Fig. 2). Power was calculated in 0.49-Hz frequency bins and averaged across the appropriate frequencies to obtain the power values for theta (4–8 Hz), slow alpha (8–10 Hz), fast alpha (10–12 Hz), slow beta (12–20 Hz), and fast beta (20–28 Hz)."
Has anyone come across this issue before and know how to get around it? Any advice would be appreciated!
Hi Johnny,
You need to code a little bit, the "spectopo" function is a good place to start.
HTH.
Samer
Hi,
if you call spectopo (or pop_spectopo) from script, you can get the output, for example:
[spectopo_outputs, freqs]= pop_spectopo(EEG, 1, [], 'EEG' , 'winsize' , 512, ...
'plot', 'on', 'freqrange',[0 100],'electrodes','on', 'overlap', 0);
The output (spectopo_outputs) will be a matrix with dimensions of channels and frequencies (e.g. 64*513). The freqs variable will give you the frequencies from around 0 to something like 256 Hz (depends on the parameters).
Hi Endre,
Your advice is exactly what I was looking for. Thank you so much for your help!
Many thanks,
Johnny.
I have lots of teaching resources on my website, including books and recorded lectures, mostly about time-frequency analysis and other EEG-related signal processing techniques. Maybe you'll find some of this material useful.
mikexcohen.com
Hey Johnny Parr did you managed to do the calculations? I'm trying to do the same, is there a chance that you can tell me how you did it or to share the script?
Regards
Hi Jorge Darío López Sánchez . Yes thankfully I'm up to scratch with the basics of these calculations now. My code is primarily written in Matlab. Be aware that these calculations are dependent on the various specifics of your data so modifications (that can be confusing) will always be necessary. If you like, we can open an email correspondence. My email is [email protected]. Send me a brief overview of what it is your trying to analyse and i'll do my best to try and help you out.
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