[Eeglablist] How do I measure ratio of EEG frequency band for a few electrodes in decibels?

Tarik S Bel-Bahar tarikbelbahar at gmail.com
Mon Aug 28 11:05:30 PDT 2017

Hello Goh, a few notes below:


Your best bet is to use a calculation based on a published recent papers in
high-quality journals.
Such ratios are also used in QEEG research, so also look in that literature.

If you have questions about basic theory/maths of frequency computations,
see Mike X. Cohen's excellent book, and related website materials. I may be
wrong, but I don't frequency computations in eeglab lead to results in
microvolts. Please review function documentation, and labels on axes of
spectral graphs from eeglab for more info.

See also past eeglablist posts on this topic by googling eeglablist + your

On Sun, Aug 27, 2017 at 11:42 AM, goh victor <saltnote at hotmail.com> wrote:

> I wanted to calculate the ratio of Theta/Beta in decibels for a couple of
> electrodes in AF3 AF4 and Cz
> I was able to get these in microvolts, but would like to convert them to
> decibels but am unsure what is the appropriate way to do so.
> For instance, should I convert it like:
>     ratio1 = 10Log((Theta(AF3) + Theta(AF4) + Theta(Cz))/(Beta(AF3) +
> Beta(AF4) + Beta(Cz)))
> or
>     ratio2 = 10Log(Theta(AF3)/Beta(AF3)) + 10Log(Theta(AF4)/Beta(AF4)) +
> 10Log(Theta(Cz)/Beta(Cz))
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