<div dir="ltr">Hi Jan (and Vitória),<div><br></div><div>Thank you for the explanation!</div><div><br></div><div>Are the methods you proposed implemented in Fieldtrip in any way?</div><div><br></div><div>José</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Jul 10, 2015 at 5:12 PM, Vitória Piai <span dir="ltr"><<a href="mailto:v.piai.research@gmail.com" target="_blank">v.piai.research@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div bgcolor="#FFFFFF" text="#000000">
Hi Jose, <br>
<br>
Just adding two helpful references that further clarify
Jan-Mathijs's point:<br>
<br>
"Fourier-, Hilbert- and wavelet-based signal analysis: are they
really different approaches?"<br>
<a href="http://www.ncbi.nlm.nih.gov/pubmed/15262077" target="_blank">http://www.ncbi.nlm.nih.gov/pubmed/15262077</a><br>
<br>
"Comparison of Hilbert transform and wavelet methods for the
analysis of neuronal synchrony"<br>
<a href="http://www.sciencedirect.com/science/article/pii/S0165027001003727" target="_blank">http://www.sciencedirect.com/science/article/pii/S0165027001003727</a><br>
<br>
Cheers, Vitoria<br>
<br>
<blockquote type="cite"><div><div class="h5">
<div>On 7/9/2015 7:24 AM, Schoffelen, J.M.
(Jan Mathijs) wrote:<br>
</div>
</div></div><blockquote type="cite"><div><div class="h5">
Jose,
<div><br>
</div>
<div>
<div>
<blockquote type="cite">
<div dir="ltr">
<div>Regarding the time-resolved PLV, isn't it different
to do it with mtmconvol, which in my view provides a
TFR, than with a time signal based on the Hilbert
transform which estimates instantaneous phase.</div>
<div><br>
</div>
<div>My doubt is that the time-resolved PLV will need
three or four cycles for good spectral estimation, and
two things can happen:</div>
<div>1 - I analyse non-overlapping chunks and get a low
number of time-points.</div>
<div>2 - I analyse highly overlapping segments and thus
a lot of PLV estimations but not really independent
from each other and therefore biasing the comparison
to other conditions</div>
<div><br>
</div>
<div>With the Hilbert derived transform I would
theoretically have as many independent estimates of
the PLV, right?</div>
<div><br>
</div>
<div>Is there a caveat in my line of thought? I might be
missing something here…</div>
</div>
</blockquote>
<div><br>
</div>
<div>The thing you are missing here, is that the Hilbert
transform also integrates over time to get an
‘instantaneous’ estimate of phase and amplitude (in other
words, there’s nothing instantaneous about it). The
difference with Fourier based methods is that you
explicitly have to set the time window when doing a short
window FFT, and for the Hilbert transform (which by the
way in MATLAB is computed through a Fourier transform as
far as I remember) one only can guess about how
independent the time samples are from one sample to the
next. Note, that temporal overlap is not so much an issue
when doing statistical inference by means of permutation
tests.</div>
<div><br>
</div>
<div>Best,</div>
<div>Jan-Mathijs</div>
<div><br>
</div>
</div>
</div>
<br>
<div>
<div style="color:rgb(0,0,0);letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;word-wrap:break-word">
<div style="color:rgb(0,0,0);letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;word-wrap:break-word">
<div style="color:rgb(0,0,0);letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;word-wrap:break-word"> Jan-Mathijs
Schoffelen, MD PhD, Senior researcher
<div><br>
Max Planck Institute for Psycholinguistics<br>
Donders Centre for Cognitive Neuroimaging</div>
<div><br>
E-mail: <a href="mailto:j.schoffelen@donders.ru.nl" target="_blank">j.schoffelen@donders.ru.nl</a><br>
Telephone: <a href="tel:%2B31-24-3614793" value="+31243614793" target="_blank">+31-24-3614793</a><br>
<br>
<a href="http://www.hettaligebrein.nl" target="_blank">http://www.hettaligebrein.nl</a></div>
<div><a href="http://www.fieldtriptoolbox.org" target="_blank">http://www.fieldtriptoolbox.org</a></div>
</div>
</div>
</div>
</div>
<br>
<br>
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<br>
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</blockquote>
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