[Eeglablist] The meaning of dB

[Arnaud Delorme]

> I have a couple of questions concerning how the timef function 
> calculates the power.
> 1- the timef function measures the post-stimulus power with respect to 
> a pre-stimulus (baseline) power and this is calculated in decibels 
> using 10*log10(Post-stimulius Power/Pre-stimulius Power). Is this 
> correct?

Yes, this is exactly right.

> 2- I'm interested in knowing what the original values (in microvolts) 
> are of the pre-stimulus and post-stimulus data. Can the raw values for 
> pre-stim and post-stim amplitudes  be determined in EEGLAB?

Yes, put the baseline value to "NaN" ('baseline', 'NaN') and it will be 
subtract (in log space) the baseline.

Best,

Arno