[FieldTrip] which baseline correction to choose for frequency analysis

[KatrinH Heimann]

Thanks Max! That helped! I will indeed not do the baseline correction! k


2014-05-29 12:20 GMT+02:00 Stenner, Max-Philipp <
max-philipp.stenner at med.ovgu.de>:

> Hi Katrin,
>
> it sounds like you will end up using 'depsamplesT' as your statistic
> (because you compare repeated measures = 2 consecutive time intervals from
> the same subject or trial) - why do you need to use baseline-correction
> then? The pairing should already account for differences in baseline power
> between subjects (or trials). If you do need a baseline correction, I would
> not choose such a short baseline in the frequency domain, but go for an
> average over a much longer (.5 to 1 second) interval, particularly if you
> intend to baseline-correct single trials (because a short baseline is more
> likely to project noise from the baseline into your interval of interest).
> Also, keep in mind that ft_freqanalysis computes power across a time window
> (specified by you in cfg.t_ftimwin), so that power between -.1 and 0 may
> not only reflect "baseline" power.
>
> Best
>
> Max
>
>
>
> ________________________________
>
> Von: fieldtrip-bounces at science.ru.nl [fieldtrip-bounces at science.ru.nl]"
> im Auftrag von "KatrinH Heimann [katrinheimann at gmail.com]
> Gesendet: Donnerstag, 29. Mai 2014 11:55
> An: FieldTrip discussion list
> Betreff: [FieldTrip] which baseline correction to choose for frequency
> analysis
>
> Hey together,
> another rather conceptual question:
> I am wondering about the baselinecorrection for the frequencyanalysis.
> I want to compare two timeperiods of one second each, lying right after
> each other.
> In the preprocessing I have baseline corrected them using 100 ms before
> the first piece (last part of a fixationcross period).
> Do I use the same part for the frequencyanalysis? Will say, do I run the
> analysis let's say from -0.5 (0 point is end of fixation cross) to 2.5 s,
> correcting with [-0.1 0] and then extract the two different conditions by
> statistical extraction (each 1 second long) ? Or do I run two analysis on
> (a bit more than) one second each, using the whole trial as baseline?
>
> thanks a lot for your advice again! Best
> Katrin
>
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