[FieldTrip] Time Frequency Analysis and padding

[jan-mathijs schoffelen]

Hi Sylvia,

You can do both. Note that in specifying the cfg.pad parameter, you need to give the length of the trial including the padding, so in your example it should be >= 0.9.
The consequence of the padding will be that you can still estimate the TF-map at latencies > 0.6 s, but note that thiswill be computed from fewer observations than the power at lower latencies.

Best,

Jan-mathijs

On Sep 19, 2011, at 10:34 PM, Sylvia Guillory wrote:

> Dear FieldTrip Community,
> 
> I have a question regarding the ft_freqanalysis function. I acquired EEG data in a paradigm where each condition varied in length. For instance, the memory retention period was 600ms in one condition and 900ms in another condition. I want to perform time-frequency analysis using morlet wavelets. My question is that if my epochs are different lengths, would I need to set the cgf.pad parameter to pad the 600ms condition by 300ms so that they are the same length or is it recommend that when I segment the data that I produce longer epochs for my time of interest in the 600ms condition? Thank you for your time.
> 
> -Sylvia
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Jan-Mathijs Schoffelen, MD PhD 
Donders Institute for Brain, Cognition and Behaviour, 
Centre for Cognitive Neuroimaging,
Radboud University Nijmegen, The Netherlands
J.Schoffelen at donders.ru.nl
Telephone: +31-24-3614793

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