<div dir="ltr"><div class="gmail_default" style="color:rgb(51,51,153)">Hi Fabio, some notes below!</div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)">-you can take/use all 128 channels if you wish, some researchers cut off the lowest channels across the head to reduce noise from face and neck. Would bring you closer to 90 channels, and would remove the fuller coverage of the head that the 128 channels provide.</div><div class="gmail_default" style="color:rgb(51,51,153)">-one usually puts into ICA whatever channels are not marked as bad/dirty/noisy. </div><div class="gmail_default" style="color:rgb(51,51,153)">-for good ica, one does not want large patches of the montage to be missing electrodes because of a "too-heavy" bad channel procedure, so there are trade-offs in taking more or less channels.</div><div class="gmail_default" style="color:rgb(51,51,153)">-interpolation of bad channels before ICA is not recommended, as it adds "extra info" into the data. Better to interpolate after ICA if you have to. Remember that once you are working with ICs you have gone beyond channels, and can focus on the ICs.</div><div class="gmail_default" style="color:rgb(51,51,153)">-after data has bad ICs removed, one can of course look at channels of interest</div><div class="gmail_default" style="color:rgb(51,51,153)">-see makoto's pipeline, eeglab tutorial, and past eeglablist discussion on this topic</div><div class="gmail_default" style="color:rgb(51,51,153)">-consider reviewing other approaches for ICA focusing on specific bands or using different techniques including wavelets.</div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)"><br></div><div class="gmail_default" style="color:rgb(51,51,153)"></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Jul 18, 2018 at 2:18 PM, Giatsidis, Fabio <span dir="ltr"><<a href="mailto:fabio_giatsidis@brown.edu" target="_blank">fabio_giatsidis@brown.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">
<div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">Hello EEGLAB list,</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial"><br></div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">I have a (probably naive) question regarding ICA.<br></div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">I have been using an <span style="font-size:12.8px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">EGI 128-channel system to record resting states. I have been reading a bit about ICA, but </span>it is still not clear to me:</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">- whether I should or not choose the whole 128 channel set for running ICA, and</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">- consequently, how I should <i>a priori</i> decide which channels to consider for ICA and which not.</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial"><br></div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">The recordings are ~2 minutes long and the sampling rate is 1000 Hz. I would like to keep as many channels as possible during pre-processing, and afterwards discard the ones I realize are not useful to my analysis - if this approach seems reasonable.</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial"><br></div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">Also:</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">- if as a very first step I delete some clearly bad channels and then interpolate them to repopulate the original channel set, is it legit to include such interpolated channels during ICA?</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial"><br></div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">Thank you very much!</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">Best,</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">-Fabio</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial"><br></div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">------------------------------<wbr>--</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial"><i>Fabio Giatsidis, M.D.</i></div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">Resident in Neurology - University of Rome "Tor Vergata" - Rome, Italy</div><div style="font-size:small;text-decoration-style:initial;text-decoration-color:initial">Post-doctoral research fellow - Brown University - Providence, RI, USA</div></div>
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