Hello!

I am currently conducting a comparison of alpha and theta band power across different age groups. I'm exploring the differences between the conventional approach (comparisons using Power Spectral Densities (PSDs) with both periodic and aperiodic components) and the parameterisation of the data (using PSDs of just the periodic components).

I plotted both PSDs to take a look at the data, but I realised that the highest value in my regular PSD went up to 70, while the highest value in my parameterized PSD was 80.

I'm not too sure if I've done something wrong because to my understanding, the parameterised PSD should actually show smaller values, since you'd be subtracting the power contributions from the aperiodic components, while the regular PSD reflects both components.

This is what I did to compute my values, maybe I did something wrong along the way. For my regular PSD, I computed Welch's PSD with a 4s Hamming window and 50% overlap segments. I then ran that through the FOOOF algorithm to extract the peaks.

I realised that when I extracted the values for my regular PSD, the values were very small (E-12). Meanwhile, the values I extracted from the FOOOF peaks were relatively larger (E+00), so I wasn't sure how to interpret these units. I did a bit of searching on these discussions and came across these threads:

So I figured that the units in the FOOOF peaks are already in μV2/Hz, while the regular PSD was in signal units and needed to be transformed to microV. I divided my regular PSD units by (1e-6)^2. I assumed that meant that both units from the regular PSD and FOOOF PSD were comparable now, but maybe I was wrong to assume so.

I would greatly appreciate any insight to this matter, many thanks in advance!

Jonas