non-uniform trial length

Marijn van Wingerden ewingerd at SCIENCE.UVA.NL
Fri Jan 11 10:22:04 CET 2008

Hi Fieldtrippers,

Recently, I've begun trying to use FieldTrip to analyse LFP traces from
rats implanted with tetrode arrays. I would like to look at changes in
power over a range of frequencies in relation to behavioural events. So,
likely, I will use freqanalysis_tfr as a method for this. Since I'm
interested in /changes/ in power from baseline, I would probably have to
use freqbaseline with the 'relative change' method. Looking at the code
for this function, it seems that it expects a baseline period somewhere
before the event of interest, for each trial.

In my research, the rats are freely moving around a cage, so there is no
fixed interval between the end of the baseline period and the start of
the peri-event interval of interest. As I see it, the baselinefreq
function requires the baseline period to be a fixed part of any trial.

Is there already a way to pass a full, pre-made freq.powspctrm (from the
baseline periods) to the freqbaseline function? I noticed that the
subfunction TFrelchange indexes into the event intervals. I guess I
could rewrite that part as a private function to accept such a baseline
freq.powspctrm, but I'm wondering if such a tool already exists.

Alternatively, I guess I could create a 'trialfun' function that
stitches the baseline and event part of the data together on a
trial-by-trial basis, resulting in a uniform trial length.

I would greatly appreciate any feedback on whether to go with A or B, or
which solution would work the best in the FieldTrip framework,




Mr. Marijn van Wingerden, M.Sc.
PhD-candidate Animal Physiology & Cognitive Neuroscience (APCN)
Centre for NeuroScience (CNS) section of
Swammerdam Institute for Life Sciences (SILS)
University of Amsterdam, Faculty of Science
Kruislaan 320, 1098 SM Amsterdam, The Netherlands
Tel: +31 20 525 7713/7547
Fax: +31 20 525 7709

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