[Eeglablist] Can I do ERSP for epochs of 1.25 sec duration?

[Scott Makeig]

Eric -

In your case, if you are interested in rel. low frequency effects,
which may have long latencies, then you really have no stable baseline
period. Therefore it may be more effective to use the entire epoch (or
a long basline period) for the ERSP baseline. Since the first spectral
window must be within the data epoch, the *center* of the (lowest)
frequency window should then be before the time-locking event in order
to measure event related changes in the EEG (source) spectra.

If you are time-locking on the movement cue, it might be useful to
have a 1.25-s (one whole trial) pre-stimulus period, and then at least
a 1.25-s + one-half-window post-event duration (e.g. about 2 s).

Scott Makeig

PS If you are looking for brief/early higher-frequency spectral
responses, you  might try out the new 'spectral time warping' feature
of erpimage().

On 1/8/07, Eric Landsness <landsness at wisc.edu> wrote:
> If my experimental events occur frequently (every 1.25 seconds) can I legitimately do ERSP time/frequency analysis?
>
> Background: A subject is repeatedly (90 trials) primed to perform a motor movement every 1.25 sec, where the movement takes about 750 msec to complete.  I realize that typically we use -1s to +2s for time/freq analysis because event-related changes in the EEG need time to develop and to recover.  In this situation can I get away with using -0.25s to 0 for my baseline and 0 to +1s for my post-event activity?
>
> If the eeglablist feels that I can't do ERSP, I can still perform ICA, correct?  The ideal situation would be to perform ICA and then feed the independent components into timef.
>
> Thank you,
> Eric
> PhD student
>
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-- 
Scott Makeig, Director and Research Scientist, Swartz Center for
Computational Neuroscience, Institute for Neural Computation,
University of California San Diego, La Jolla CA 92093-0961,
http://sccn.ucsd.edu/~scott