<div>1. not sure if you have to decimate, have seen some people to do this to better meet requirements for good ICA decompositions.</div><div>2. don't think higher sampling rate will give you better ICA. I think it's more of a matter that ICA is fed data that gives an accurate and lengthy representation of the whole "Data space".</div>
<div>3. quote from earlier eeglablist post: "<span style>the key factor is how much data you have (</span><span class="il" style>timepoints</span><span style> / </span><span class="il" style>channels</span><span style>^2). If this is > 30 (or near to it), then we find it preferable to return all possible components (since pca does a rather poor job of separating sources)."</span></div>
<div><span style>So if below this threshold there is some reason for adding more time to the protocol, or reducing channels, or decimation</span></div><br>
<br><br><div class="gmail_quote">On Tue, Mar 13, 2012 at 6:00 AM, Modestino, Edward J *HS <span dir="ltr"><<a href="mailto:EJM9F@hscmail.mcc.virginia.edu">EJM9F@hscmail.mcc.virginia.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div lang="EN-US" link="blue" vlink="purple"><div><p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">Dear EEGLAB experts,<u></u><u></u></span></p><p class="MsoNormal">
<span style="font-family:"Times New Roman","serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">(1) Is it true that ICA must be subject, like all the model-based spectral analysis methods, to a recommendation that one decimate to the lowest frequency capable of representing the actual signal content of the data without alienation effects? <b>Does one <u>NEED</u> to decimate the data before running ICA?</b> For instance, we have a data set recorded at 1,000 Hz. Do we need to decimate this to approximately 128 or 256?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">(2 ) According to the formula that Dr. Makeig gave to determine the optimal amount of data, <b>#timepoints/(#channels)^2</b>, it would appear that a <b>higher sampling rate will give better ICA results</b>. Is this the case?<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">(3) Finally, using this formula, <b>#timepoints/(#channels)^2</b>, is there a <b>threshold or cutoff</b> one needs to be exceeded to have the optimal amount of data to run ICA. Simply doing the equation without any way to interpret the output is not helpful.<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">Thanks for your help,<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">Dr. Modestino<u></u><u></u></span></p><p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d"><u></u> <u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">Edward Justin Modestino, Ph.D.<u></u><u></u></span></p><p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">Postdoctoral Research Associate<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">Ray Westphal Neuroimaging Laboratory<u></u><u></u></span></p><p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">Division of Perceptual Studies<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">Department of Psychiatry and Neurobehavioral Sciences <u></u><u></u></span></p><p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">University of Virginia<u></u><u></u></span></p>
<p class="MsoNormal"><span style="font-family:"Times New Roman","serif";color:#1f497d">Email: <a href="mailto:ejm9f@virginia.edu" target="_blank">ejm9f@virginia.edu</a><u></u><u></u></span></p><p class="MsoNormal">
<span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p><p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1f497d"><u></u> <u></u></span></p>
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