<div dir="ltr">Dear Karlo,<div><br></div><div style>ICA is to generate spatial filter (EEG.icaweight*EEG.icasphere) and IC activities. Scalp channel EEG remains unaffected.<br></div><div style><br></div><div style><span style="font-size:12.666666984558105px;background-color:transparent;font-family:'times new roman','new york',times,serif">>Indeed, i like to know: how ICA may affect the coherency</span><span style="font-size:12.666666984558105px;background-color:transparent;font-family:'times new roman','new york',times,serif"> between channel_1 (alpha-band) and channel_2</span><span style="font-size:12.666666984558105px;background-color:transparent;font-family:'times new roman','new york',times,serif"> (beta-band)? </span><br>
</div><div class="gmail_extra"><br></div><div class="gmail_extra">ICA does not change anything, it just generates parallel data.</div><div class="gmail_extra"><br></div><div class="gmail_extra">Makoto<br><br><div class="gmail_quote">
2013/4/3 karlo gonzales <span dir="ltr"><<a href="mailto:thats_karlo@yahoo.com" target="_blank">thats_karlo@yahoo.com</a>></span><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">
<div><div style="font-size:10pt;font-family:arial,helvetica,sans-serif"><div style="font-family:arial,helvetica,sans-serif;font-size:10pt"><span>Thanks for your prompt reply. and </span><font style="background-color:transparent">my apology, if my question was not clear enough.</font></div>
<div style="font-style:normal;font-size:12.800000190734863px;background-color:transparent;font-family:arial,helvetica,sans-serif"><font style="background-color:transparent"> My concern is not about </font><span style="background-color:transparent"><font face="times new roman, new york, times, serif">phases between channels and ICs. </font></span><span style="font-family:'times new roman','new york',times,serif;background-color:transparent">Indeed, i like to know: how ICA may affect the coherency</span><span style="font-family:'times new roman','new york',times,serif;background-color:transparent"> between channel_1 (alpha-band) and channel_2</span><span style="font-family:'times new roman','new york',times,serif;background-color:transparent"> (beta-band)? does ICa will shift phase of alpha or beta?</span></div>
<div style="font-style:normal;font-size:12.800000190734863px;background-color:transparent;font-family:'times new roman','new york',times,serif"><span style="font-family:'times new roman','new york',times,serif;background-color:transparent"><br>
</span></div><div style="font-style:normal;font-size:12.800000190734863px;background-color:transparent;font-family:'times new roman','new york',times,serif"><span style="font-family:'times new roman','new york',times,serif;background-color:transparent">Thanks again,</span></div>
<div><span style="font-family:'times new roman','new york',times,serif;background-color:transparent">Karlo</span></div><div style="font-style:normal;font-size:12.800000190734863px;background-color:transparent;font-family:'times new roman','new york',times,serif">
<span style="font-family:'times new roman','new york',times,serif;background-color:transparent"><br></span></div><div class=""><div style="font-style:normal;font-size:13.600000381469727px;background-color:transparent;font-family:arial,helvetica,sans-serif">
<br></div><div style="font-family:arial,helvetica,sans-serif;font-size:10pt"><br></div> </div><div style="font-family:arial,helvetica,sans-serif;font-size:10pt"><div class=""> </div><div style="font-family:'times new roman','new york',times,serif;font-size:12pt">
<div class=""> <div dir="ltr"> <font face="Arial"> <hr size="1"> <b><span style="font-weight:bold">From:</span></b> Makoto Miyakoshi <<a href="mailto:mmiyakoshi@ucsd.edu" target="_blank">mmiyakoshi@ucsd.edu</a>><br>
<b><span style="font-weight:bold">To:</span></b> karlo gonzales <<a href="mailto:thats_karlo@yahoo.com" target="_blank">thats_karlo@yahoo.com</a>> <br><b><span style="font-weight:bold">Cc:</span></b> EEGLAB List <<a href="mailto:eeglablist@sccn.ucsd.edu" target="_blank">eeglablist@sccn.ucsd.edu</a>> <br>
<b><span style="font-weight:bold">Sent:</span></b> Wednesday, April 3, 2013 9:36:51 PM<br> <b><span style="font-weight:bold">Subject:</span></b> Re: phase shift and ICA<br> </font> </div></div><div><div class="h5"> <br>
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<div dir="ltr">Dear Dr. Gonzales,<div><br></div><div>I suppose you mean you compare phases between channels and ICs. It's not shift that makes difference between scalp channel ICs and EEGs. Let me explain what it is. Let's say we have only 2 channels and 2 ICs. The relation of scalp channel EEG and ICs are like this:</div>
<div><br></div><div>Channel 1 = 0.3 X IC1 + 0.7 X IC2</div><div>Channel 2 = 0.7 x IC1 + 0.3 x IC2</div><div><br></div><div>Here I determined 0.3 and 0.7 arbitrarily but actually these are determined by ICA. Anyway, when you compare Channel 1 with IC1 in the above example, they are dissimilar to each other NOT because of phase shift (unless IC1 and IC2 are similar, which is hard to imagine since they are supposed to be temporally independent).</div>
<div><br></div><div>If the decomposition is like</div><div><br></div><div><div>Channel 1 = 0.99999 X IC1 + 0.00001 X IC2</div><div>Channel 2 = 0.00001 x IC1 + 0.99999 x IC2</div></div><div>
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</div><div>Then your Channel 1 and IC1 should be very similar.</div><div><br></div><div>Makoto</div><div><br></div></div><div><br><br><div>2013/4/3 karlo gonzales <span dir="ltr"><<a rel="nofollow" href="mailto:thats_karlo@yahoo.com" target="_blank">thats_karlo@yahoo.com</a>></span><br>
<blockquote 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"><div><div style="font-size:10pt;font-family:arial,helvetica,sans-serif"><div>
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<div style="font-size:10pt;font-family:arial,helvetica,sans-serif">Dear Dr.<span style="font-size:small;color:rgb(34,34,34);font-family:arial,sans-serif;line-height:16px"> </span><i>Miyakoshi,</i></div><div style="font-style:normal;font-size:13px;background-color:transparent;font-family:arial,sans-serif">
<i><br></i></div><div style="background-color:transparent"><span><span><font><i><span><span style="line-height:16px">I am using EEGLAB and ICA tools to clean EEG data. i am recording EEG from a 64 channel cap (NEUROSCAN), with a fixed reference electrode, which is located between CZ and CPZ. </span></span></i></font></span></span></div>
<div style="background-color:transparent"><font face="arial, sans-serif"><i><span style="line-height:16px">i do not re-reference my data for further analysis.</span></i></font><i style="line-height:16px;font-size:13px;font-family:arial,sans-serif;background-color:transparent"> So, i just wonder, if applying ICA, would shift the phase of signals (specially low frequency)? is there anyway to check it? </i></div>
<div style="background-color:transparent"><i style="line-height:16px;font-size:13px;font-family:arial,sans-serif;background-color:transparent"><br></i></div><div style="background-color:transparent"><i style="line-height:16px;font-size:13px;font-family:arial,sans-serif;background-color:transparent">many many thanks for all your help and support,</i></div>
<div style="background-color:transparent"><i style="line-height:16px;font-size:13px;font-family:arial,sans-serif;background-color:transparent">Karlo</i></div><div style="background-color:transparent"><span><span><font><span style="line-height:16px"><i><br>
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<span><span style="line-height:16px;font-style:italic;font-size:13px;font-family:arial,sans-serif"><br></span></span></div><div style="font-style:italic;font-size:13px;background-color:transparent;font-family:arial,sans-serif">
<span><span style="line-height:16px;font-style:italic;font-size:13px;font-family:arial,sans-serif"><br></span></span></div></div></div></div></div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br><div dir="ltr">
Makoto Miyakoshi<br>Swartz Center for Computational Neuroscience<br>Institute for Neural Computation, University of California San Diego<br></div>
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</div><br><br> </div></div></div> </div> </div></div></blockquote></div><br><br clear="all"><div><br></div>-- <br><div dir="ltr">Makoto Miyakoshi<br>Swartz Center for Computational Neuroscience<br>Institute for Neural Computation, University of California San Diego<br>
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