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<p class=MsoNormal>Hello,<o:p></o:p></p>
<p class=MsoNormal>I just now came across the FieldTrip toolbox and have a few
questions – I apologize in advance if I am misusing this discussion forum
or if my questions are too obvious. I am working with a very large
dataset of simultaneous LFP, unit, and NIRS signal from macaques for the
purpose of examining time and frequency dynamics of the signals in various
cognitive conditions. I would like to implement the clustering/bootstrapping
methodology outlined in [Journal of Neuroscience Methods 164 (2007)
177–190] to identify significant changes in synchronization and phase-locking.
<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The specific data in question are LFPs recorded while the
monkeys perform a working-memory task, which consists of a 2s visual sample,
20s delay, and subsequent choice period. A 20s baseline precedes the
sample (t=0), which is time-locked to the animal’s foveation on the
visual sample. TF plots are computed using Morlet wavelets for each trial,
averaged across trials, and then normalized with respect to the average
baseline. The first question I’d like to address is: what
time-frequency regions exhibit significant difference between Correct (left
plot) and Incorrect (right plot) trials. <o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><img width=352 height=264 id="Picture_x005f_x0020_2"
src="cid:image001.jpg@01CACC76.97F36B40"
alt="cid:image002.jpg@01CAA0E0.B7CEC3E0"> <img width=352 height=264
id="Picture_x005f_x0020_3" src="cid:image002.jpg@01CACC76.97F36B40"
alt="cid:image003.jpg@01CAA0E0.B7CEC3E0"><o:p></o:p></p>
<p class=MsoNormal>I have a number of questions about the appropriateness of
applying bootstrapping to our specific dataset:<o:p></o:p></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><span
style='mso-list:Ignore'>1)<span style='font:7.0pt "Times New Roman"'>
</span></span><![endif]>Because we use wavelets for spectral decomposition (with
frequency-dependent changes in spectral and temporal resolution) is it valid to
simply cluster across different frequencies?<o:p></o:p></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><span
style='mso-list:Ignore'>2)<span style='font:7.0pt "Times New Roman"'>
</span></span><![endif]>We are interested in comparing different conditions, where
each is computed relative to its own baseline. Is there anything wrong
with using the baselines of the same dataset for the null distribution as
opposed to using a different set of baseline data?<o:p></o:p></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><span
style='mso-list:Ignore'>3)<span style='font:7.0pt "Times New Roman"'>
</span></span><![endif]>The data have been recorded at 1KHz, and this
oversampling results in high spatial-frequency noise. Do I need to do any
downsampling/smoothing before applying the statistics?<o:p></o:p></p>
<p class=MsoListParagraph style='text-indent:-.25in;mso-list:l0 level1 lfo2'><![if !supportLists]><span
style='mso-list:Ignore'>4)<span style='font:7.0pt "Times New Roman"'>
</span></span><![endif]>For evaluating the relationship between channels, we compute
the phase-locking value (PLV), which has no meaningful single-trial measuremetnt.
Is there any way to apply statistical analyses directly to the average TF plots
without resorting back to the individual trials?<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Thank you in advance for your help!<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span style='font-size:10.5pt;font-family:Consolas'>__________________________________________________________________________________</span><o:p></o:p></p>
<p class=MsoNormal>Allen Ardestani Email: <a
href="mailto:aardesta@ucla.edu">aardesta@ucla.edu</a><o:p></o:p></p>
<p class=MsoNormal>Phone: (310) 825-5528<o:p></o:p></p>
<p class=MsoNormal>Medical Scientist Training Program<o:p></o:p></p>
<p class=MsoNormal>David Geffen School of Medicine at UCLA<o:p></o:p></p>
<p class=MsoNormal>Semel Institute for Neuroscience and Human Behavior<o:p></o:p></p>
<p class=MsoNormal>760 Westwood Plaza<o:p></o:p></p>
<p class=MsoNormal>Los Angeles, CA 90095-1759<o:p></o:p></p>
<p class=MsoNormal>USA<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
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<p>----------------------------------</p>
<p>The aim of this list is to facilitate the discussion between users of the FieldTrip toolbox, to share experiences and to discuss new ideas for MEG and EEG analysis.</p>
<p> http://listserv.surfnet.nl/archives/fieldtrip.html</p>
<p> http://www.ru.nl/fcdonders/fieldtrip/</p>