<div dir="ltr">Dear Iman,<div><br></div><div><p class="MsoNormal"><span style="font-size:9.5pt;font-family:Minion-Regular;color:black">> Using causal filter may adversely effect the direction of information<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.5pt;font-family:Minion-Regular;color:black">flow in the GC analysis. It is recommended that one use a<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.5pt;font-family:Minion-Regular;color:black">non-causal filter (for example, finite impulse response filters) with<u></u><u></u></span></p><p class="MsoNormal"><span style="font-size:9.5pt;font-family:Minion-Regular;color:black">zero phase lag</span></p></div><div class="gmail_extra"><br></div><div class="gmail_extra">Really? The impulse response of the non-causal FIR filter spreads in both ways in the time domain, which means info of future events leak to past... I thought using causal filter with minimum phase makes more sense.</div><div class="gmail_extra"><br></div><div class="gmail_extra">Makoto</div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Jun 23, 2015 at 4:29 PM, Iman Mohammad-Rezazadeh <span dir="ltr"><<a href="mailto:irezazadeh@ucdavis.edu" target="_blank">irezazadeh@ucdavis.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex">
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<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Minion-Regular;color:black"><a href="http://journal.frontiersin.org/article/10.3389/fnhum.2015.00194/abstract" target="_blank">http://journal.frontiersin.org/article/10.3389/fnhum.2015.00194/abstract</a><u></u><u></u></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Minion-Regular;color:black"><u></u> <u></u></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Minion-Regular;color:black">Using causal filter may adversely effect the direction of information<u></u><u></u></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Minion-Regular;color:black">flow in the GC analysis. It is recommended that one use a<u></u><u></u></span></p>
<p class="MsoNormal" style="text-autospace:none"><span style="font-size:9.5pt;font-family:Minion-Regular;color:black">non-causal filter (for example, finite impulse response filters) with<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-size:9.5pt;font-family:Minion-Regular;color:black">zero phase lag (</span><span style="font-size:9.5pt;font-family:Minion-Regular;color:rgb(115,115,115)">Mullen et al., 2012</span><span style="font-size:9.5pt;font-family:Minion-Regular;color:black">,
Coben and Rezazadeh, 2015) <u></u><u></u></span></p>
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<p class="MsoNormal"><a name="14e22c10c4aae8fe__MailEndCompose"><span style="font-size:11pt;font-family:Calibri,sans-serif;color:rgb(31,73,125)"><u></u> <u></u></span></a></p>
<p class="MsoNormal"><b><span style="font-size:11pt;font-family:Calibri,sans-serif">From:</span></b><span style="font-size:11pt;font-family:Calibri,sans-serif"> <a href="mailto:eeglablist-bounces@sccn.ucsd.edu" target="_blank">eeglablist-bounces@sccn.ucsd.edu</a> [mailto:<a href="mailto:eeglablist-bounces@sccn.ucsd.edu" target="_blank">eeglablist-bounces@sccn.ucsd.edu</a>]
<b>On Behalf Of </b>Makoto Miyakoshi<br>
<b>Sent:</b> Tuesday, June 23, 2015 2:07 PM<br>
<b>To:</b> Vito De Feo<br>
<b>Cc:</b> EEGLAB List<br>
<b>Subject:</b> Re: [Eeglablist] Effect of anti-aliasing low-pass filter on connectivity analysis<u></u><u></u></span></p><div><div class="h5">
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<p class="MsoNormal">Thank you Vito for your response. Forgive me to ask you one more question.<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">As the ERP handbook by Luck (or his other book) recommends, anti-aliasing should better have the margin of 4-5 times of the new sampling rate e.g. if you downsample signlas to 250 Hz, anti-aliasing low-pass at 125 Hz is the standard, but
recommendation is 75 Hz or even 50 Hz. Well, I haven't tested it myself so I am not sure what bad it would do if I use 125 Hz (any comment on this, anyone?) but in this case, I guess the anti-aliasing low-pass filter does affect the subsequest connectivity
analysis--am I correct (assuming that I analyze EEG up to 50 Hz)?<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">Makoto<u></u><u></u></p>
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<p class="MsoNormal">On Mon, Jun 22, 2015 at 9:31 AM, Vito De Feo <<a href="mailto:vito.defeo@zmnh.uni-hamburg.de" target="_blank">vito.defeo@zmnh.uni-hamburg.de</a>> wrote:<u></u><u></u></p>
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<p class="MsoNormal">Dear Makoto,<br>
this will not affect the connectivity analysis if the frequency of interest are far from the Nyquist frequency. For example if you downsample to 500 Hz (Nyquist freq = 250 Hz) you will have no problem in the band 0-100 Hz.<br>
Best<br>
Vito<u></u><u></u></p>
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<p class="MsoNormal"><br>
Il giorno 20/giu/2015, alle ore 00:28, Makoto Miyakoshi ha scritto:<br>
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> Dear List,<br>
><br>
> If I use zero-phase low-pass filter for anti-aliasing, does it affect the subsequent connectivity analysis? I ask this because EEGLAB pop_resample() automatically applies it. If it does, is there a workaround? Should I use minimum phase causal filter for
anti-aliasing?<br>
><br>
> --<br>
> Makoto Miyakoshi<br>
> Swartz Center for Computational Neuroscience<br>
> Institute for Neural Computation, University of California San Diego<u></u><u></u></p>
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<p class="MsoNormal"><u></u> <u></u></p>
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<p class="MsoNormal">-- <u></u><u></u></p>
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<p class="MsoNormal">Makoto Miyakoshi<br>
Swartz Center for Computational Neuroscience<br>
Institute for Neural Computation, University of California San Diego<u></u><u></u></p>
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr">Makoto Miyakoshi<br>Swartz Center for Computational Neuroscience<br>Institute for Neural Computation, University of California San Diego<br></div></div>
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