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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I agree that zero phase lag is best. Anything else distorts the phase relationships. I know BESA proponents have argued about “future leaking into the past”,
but I think that is simply a common sense notion that is not really true globally.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I wish I could prove it mathematically, but a simple simulation should demonstrate it. Maybe I will get around to it someday.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">-Jeff Eriksen<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> eeglablist-bounces@sccn.ucsd.edu [mailto:eeglablist-bounces@sccn.ucsd.edu]
<b>On Behalf Of </b>Makoto Miyakoshi<br>
<b>Sent:</b> Tuesday, June 23, 2015 5:59 PM<br>
<b>To:</b> Iman Mohammad-Rezazadeh<br>
<b>Cc:</b> EEGLAB List<br>
<b>Subject:</b> Re: [Eeglablist] Effect of anti-aliasing low-pass filter on connectivity analysis<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Dear Iman,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:9.5pt;font-family:"Minion-Regular","serif";color:black">> Using causal filter may adversely effect the direction of information</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:9.5pt;font-family:"Minion-Regular","serif";color:black">flow in the GC analysis. It is recommended that one use a</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:9.5pt;font-family:"Minion-Regular","serif";color:black">non-causal filter (for example, finite impulse response filters) with</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:9.5pt;font-family:"Minion-Regular","serif";color:black">zero phase lag</span><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">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.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Makoto<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Tue, Jun 23, 2015 at 4:29 PM, Iman Mohammad-Rezazadeh <<a href="mailto:irezazadeh@ucdavis.edu" target="_blank">irezazadeh@ucdavis.edu</a>> wrote:<o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:"Minion-Regular","serif";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></span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:"Minion-Regular","serif";color:black"> </span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:"Minion-Regular","serif";color:black">Using causal filter may adversely effect the direction of information</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:"Minion-Regular","serif";color:black">flow in the GC analysis. It is recommended that one use a</span><o:p></o:p></p>
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<span style="font-size:9.5pt;font-family:"Minion-Regular","serif";color:black">non-causal filter (for example, finite impulse response filters) with</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:9.5pt;font-family:"Minion-Regular","serif";color:black">zero phase lag (</span><span style="font-size:9.5pt;font-family:"Minion-Regular","serif";color:#737373">Mullen
et al., 2012</span><span style="font-size:9.5pt;font-family:"Minion-Regular","serif";color:black">, Coben and Rezazadeh, 2015)
</span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><a name="14e22c10c4aae8fe__MailEndCompose"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span></a><o:p></o:p></p>
<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><b><span style="font-size:11.0pt;font-family:"Calibri","sans-serif"">From:</span></b><span style="font-size:11.0pt;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</span><o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Thank you Vito for your response. Forgive me to ask you one more question.<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">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)?<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Makoto<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"> <o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">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:<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">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<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><br>
Il giorno 20/giu/2015, alle ore 00:28, Makoto Miyakoshi ha scritto:<br>
<br>
> 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<o:p></o:p></p>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto"><span style="color:#888888">--<br>
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<p class="MsoNormal" style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Makoto Miyakoshi<br>
Swartz Center for Computational Neuroscience<br>
Institute for Neural Computation, University of California San Diego<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">-- <o:p></o:p></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<o:p></o:p></p>
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