<div dir="ltr">Dear Ana,<div><br></div><div><div style="font-family:arial,sans-serif;font-size:13.142857551574707px">>First, I was wondering wether I could use something like the 'plotchans' (available in envtopo) to compute the contributions in just one or a few channels of interest. The default function computes the contributions for the grand ERPs which gives me a lot of variability that I'm not interested in.</div>
<div style="font-family:arial,sans-serif;font-size:13.142857551574707px"><br></div><div style="font-family:arial,sans-serif;font-size:13.142857551574707px">Currently this is not supported. I see how to do it though.</div>
<div style="font-family:arial,sans-serif;font-size:13.142857551574707px">I would suggest that you exclude clusters of non-interest, or specify the clusters to use, so that your outermost envelope is consist of only necessary ones.</div>
<div style="font-family:arial,sans-serif;font-size:13.142857551574707px"><br></div><div style="font-family:arial,sans-serif;font-size:13.142857551574707px">>Also, I'm still confuse about the pvaf for the individual clusters. </div>
<div style="font-family:arial,sans-serif;font-size:13.142857551574707px">For example, I'm looking for the clusters that explain the P300 variability and there is a cluster (out of 7 clusters) that seems to me (based on the cluster's ERP) that explains most of the variability of the P300. </div>
<div style="font-family:arial,sans-serif;font-size:13.142857551574707px">When I run std_envtopo, I get a pvaf of -550.46 for that cluster. First, I understand that this is not talking about the P300 activity alone, but the grand average, and this implicates a lot of variance from many areas that I'm not interested in (and this is the reason why I'm trying to use just a few channels of interest). Therefore, because what I think is the 'P300 cluster' may have a different signal than all the other activities (that I'm not interested in), then I get a negative value for this cluster pvaf (-550.46). Am I getting something wrong so far?</div>
<div style="font-family:arial,sans-serif;font-size:13.142857551574707px"><br></div><div style="font-family:arial,sans-serif;font-size:13.142857551574707px">-550.46 should be a number of latency. Where does the line (extending from the scalp topos) pointing? Isn't it -550.46 ms? If so, you should limit the latency window to evaluate contribution.</div>
<div style="font-family:arial,sans-serif;font-size:13.142857551574707px"><br></div><div style="font-family:arial,sans-serif;font-size:13.142857551574707px">>Also, I imagine that, because this is the percent variance accounted for, for positive numbers, 100 should be the maximum possible value?<br>
</div></div><div class="gmail_extra"><br></div><div class="gmail_extra">No, actually pvaf never sums to 100% if you add up each clusters. That means, pvaf(Cls1+Cls2) ~= pvaf(Cls1)+pvaf(Cls2). By the way the default 100% is pvaf(Cls1+Cls2+...ClsN) if you have N number of clusters.</div>
<div class="gmail_extra"><br></div><div class="gmail_extra">The measure pvaf is always superadditive i.e. exceeds 100% if summed separately.</div><div class="gmail_extra"><br></div><div class="gmail_extra">Makoto<br><br>
<div class="gmail_quote">
2013/4/10 Ana Navarro Cebrian <span dir="ltr"><<a href="mailto:anavarrocebrian@gmail.com" target="_blank">anavarrocebrian@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 dir="ltr"><div><span style="border-collapse:collapse;font-family:arial,sans-serif;font-size:13px">Hi,</span><br>
</div>
<span style="border-collapse:collapse;font-family:arial,sans-serif;font-size:13px"><div>
I have two questions about the function std_envtopo.m </div><div><br></div><div>First, I was wondering wether I could use something like the 'plotchans' (available in envtopo) to compute the contributions in just one or a few channels of interest. The default function computes the contributions for the grand ERPs which gives me a lot of variability that I'm not interested in.</div>
<div><br></div><div>Also, I'm still confuse about the pvaf for the individual clusters. </div><div>For example, I'm looking for the clusters that explain the P300 variability and there is a cluster (out of 7 clusters) that seems to me (based on the cluster's ERP) that explains most of the variability of the P300. </div>
<div>When I run std_envtopo, I get a pvaf of -550.46 for that cluster. First, I understand that this is not talking about the P300 activity alone, but the grand average, and this implicates a lot of variance from many areas that I'm not interested in (and this is the reason why I'm trying to use just a few channels of interest). Therefore, because what I think is the 'P300 cluster' may have a different signal than all the other activities (that I'm not interested in), then I get a negative value for this cluster pvaf (-550.46). Am I getting something wrong so far?</div>
<div><br></div><div>Also, I imagine that, because this is the percent variance accounted for, for positive numbers, 100 should be the maximum possible value?</div><div><br></div><div>I hope that makes sense. Thanks in advance for your help.</div>
<span><font color="#888888">
<div>Ana</div></font></span></span></div>
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-- <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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