<div dir="ltr">Dear Baris,<div><br></div><div style>I give you the simple answer.</div><div style>Let's say IC1 and IC2 have regular oscillation like this <br></div><div class="gmail_extra" style><br></div><div class="gmail_extra" style>
IC1 010101010101010101</div><div class="gmail_extra" style>IC2 001001001001001001</div><div class="gmail_extra"><br></div><div class="gmail_extra">And if your channels are </div><div class="gmail_extra"><br></div><div class="gmail_extra">
Ch1 = 0.5xIC1 + 0.5xIC2</div><div class="gmail_extra"><br></div><div class="gmail_extra">Before you discard any IC, your Ch1 should be</div><div class="gmail_extra"><br></div><div class="gmail_extra">Ch1 011011011011011011</div>
<div class="gmail_extra"><br></div><div class="gmail_extra">If you discard IC1,</div><div class="gmail_extra"><br></div><div class="gmail_extra">Ch1 = 0xIC1 + 0.5xIC2</div><div class="gmail_extra"><br></div><div class="gmail_extra">
so your Ch1 will be</div><div class="gmail_extra"><br></div><div class="gmail_extra">Ch1 001001001001001001</div><div class="gmail_extra"><br></div><div class="gmail_extra">that is exactly same as IC2 in terms of phase.</div>
<div class="gmail_extra"><br></div><div class="gmail_extra" style>This is exactly what happens to the phase.</div><div class="gmail_extra" style><br></div><div class="gmail_extra" style>Makoto</div><div class="gmail_extra">
<br><div class="gmail_quote">2013/4/5 Baris Demiral <span dir="ltr"><<a href="mailto:demiral.007@gmail.com" target="_blank">demiral.007@gmail.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 bgcolor="#FFFFFF" text="#000000">
<div>Actually the question can be asked in
another way:<br>
<br>
What happens to phase information when the ICA based artifact
rejection is used, such that artifactual ICs are taken out, and
the data is reconstructed back again with the rest of the ICs? Why
would I prefer ICA correction rather than regression based
correction?<br>
<br>
Best,<br>
Baris<div><div class="h5"><br>
<br>
On 04/04/2013 11:08 AM, Makoto Miyakoshi wrote:<br>
</div></div></div>
<blockquote type="cite"><div><div class="h5">
<div dir="ltr">Dear Karlo,
<div><br>
</div>
<div>ICA is to generate spatial filter
(EEG.icaweight*EEG.icasphere) and IC activities. Scalp channel
EEG remains unaffected.<br>
</div>
<div><br>
</div>
<div><span>>Indeed, i like to
know: how ICA may affect the coherency</span><span> between channel_1
(alpha-band) and channel_2</span><span> (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>Indeed,
i like to know: how ICA may affect the coherency</span><span> between
channel_1 (alpha-band) and channel_2</span><span> (beta-band)?
does ICa will shift phase of alpha or beta?</span></div>
<div><span><br>
</span></div>
<div><span>Thanks
again,</span></div>
<div><span>Karlo</span></div>
<div>
<span><br>
</span></div>
<div>
<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> </div>
<div>
<div>
<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> <br>
<div>
<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>
<br>
</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>
<div>
<div style="font-family:arial,helvetica,sans-serif">
<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>
</i></span></font></span></span></div>
<div style="font-size:10pt;background-color:transparent;font-family:arial,helvetica,sans-serif"><span><span style="line-height:16px;font-style:italic;font-size:13px;font-family:arial,sans-serif"><br>
</span></span></div>
<div style="font-size:10pt;background-color:transparent;font-family:arial,helvetica,sans-serif"><br>
</div>
<div style="font-style:italic;font-size:13px;background-color:transparent;font-family:arial,sans-serif"><span style="font-family:arial,sans-serif;font-size:13px;font-style:italic;line-height:16px;background-color:transparent"><br>
</span></div>
<div style="font-style:normal;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 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>
</div>
</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>
</div>
</div>
</div>
<br>
<fieldset></fieldset>
<br>
</div></div><pre>_______________________________________________
Eeglablist page: <a href="http://sccn.ucsd.edu/eeglab/eeglabmail.html" target="_blank">http://sccn.ucsd.edu/eeglab/eeglabmail.html</a>
To unsubscribe, send an empty email to <a href="mailto:eeglablist-unsubscribe@sccn.ucsd.edu" target="_blank">eeglablist-unsubscribe@sccn.ucsd.edu</a>
For digest mode, send an email with the subject "set digest mime" to <a href="mailto:eeglablist-request@sccn.ucsd.edu" target="_blank">eeglablist-request@sccn.ucsd.edu</a></pre>
</blockquote>
<br>
</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>
</div></div>