[Eeglablist] ERSP baseline

[Brian Roach]

At 10:49 AM 3/13/2006, Brian Roach wrote:
>EEGlab users,
>
>I have what I hope is an easy question on the baseline period for ERSP 
>data (in timef.m).  Let's say my epochs go from -1 to 2 seconds, and my 
>window size for analysis is 128 samples.  If my AD rate is 1000Hz, and my 
>baseline period is -1 to 0, will the last FFT that contributes to the 
>average baseline power have the center of it 128 sample( or ms) window on 0,

After reading through the timef code, it seems that the baseline window 
include all the center points for the FFT window, so a -1 to 0 (seconds) 
baseline would have its last FFT window centered on either -1 or 0 (ms) and 
data from 0-63 or 64ms would contribute to the mean baseline power.  If 
anyone disagrees please let me know.


>meaning data from 0-63ms contribute to the average, or does the baseline 
>window center its last sample at -64 ms so that no data after the 0 point 
>contribute to the baseline power?  On the other hand, does it continue 
>even further than I think, and actually use an FFT from -1 to 127ms in 
>calculating the baseline average as well?
>
>I have been manipulating the "baseln" variable in the timef function for 
>different baseline periods, but I would like to have a better idea of how 
>those changes influence the ERSP data and plots.
>
>Thank you,
>Brian
>
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