Dear FieldTrippers,<div><br></div><div>I've been trying to calculate chan-chan plv, based on the connectivity tutorial (<a href="http://fieldtrip.fcdonders.nl/tutorial/connectivity?s[]=connectivity">http://fieldtrip.fcdonders.nl/tutorial/connectivity?s[]=connectivity</a>) and on past mailing-list posts. However, when I plot these plv, some plv are really high, in .8-.9 range sometimes all the way into gamma range. It is especially suspicious when channels that are in the opposite hemispheres, separated in anterior-posterior axis show such high values. Does anyone have any suggestions what might be going wrong? My script is pasted below. I'm using Waveguard cap with 128 channels in Duke layout, sampled at 512 Hz, and average-referenced, and data are analyzed using fieldtrip-20120103 version.</div>
<div><br></div><div>Thanks in advance, Akiko</div><div><br></div><div>
<p class="p1">
</p><p class="MsoNormal"><span style="font-family:Courier;color:forestgreen">%%%% first define variables</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">chans = {</span><span style="font-family:Courier;color:#a020f0">'RD7'</span><span style="font-family:Courier">,</span><span style="font-family:Courier;color:#a020f0">'LL11'</span><span style="font-family:Courier">,</span><span style="font-family:Courier;color:#a020f0">'RA2'</span><span style="font-family:Courier">,</span><span style="font-family:Courier;color:#a020f0">'LC3'</span><span style="font-family:Courier">}; </span><span style="color:rgb(34,139,34);font-family:Courier">% let's try with these first...</span></p>
<p class="MsoNormal"><span style="font-family:Courier">testTime = [.8 2.5];</span></p>
<p class="MsoNormal"><span style="font-family:Courier;color:forestgreen">%%%%</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier;color:forestgreen"> </span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier;color:forestgreen">% choose time range</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg = [];</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg.toilim =
testTime; % extract delay period</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">ft_data =
ft_redefinetrial(cfg, ft_data);</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier"> </span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier;color:forestgreen">% fourier transform</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg = [];</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg.method = </span><span style="font-family:Courier;color:#a020f0">'mtmfft'</span><span style="font-family:Courier">;</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg.taper = </span><span style="font-family:Courier;color:#a020f0">'dpss'</span><span style="font-family:Courier">;</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg.output = </span><span style="font-family:Courier;color:#a020f0">'fourier'</span><span style="font-family:Courier">;</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg.keeptrials = </span><span style="font-family:Courier;color:#a020f0">'yes'</span><span style="font-family:Courier">;</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg.keeptapers = </span><span style="font-family:Courier;color:#a020f0">'yes'</span><span style="font-family:Courier">;</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg.tapsmofrq = 2;</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg.channel =
chans; </span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">freq =
ft_freqanalysis(cfg, ft_data);</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier"> </span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier;color:forestgreen">% plv calc</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg = [];</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">cfg.method = </span><span style="font-family:Courier;color:#a020f0">'plv'</span><span style="font-family:Courier">;</span><span style="font-family:Courier"></span></p>
<p class="MsoNormal"><span style="font-family:Courier">plv =
ft_connectivityanalysis(cfg, freq);</span><span style="font-family:Courier"></span></p>
<p></p></div><div><div><br></div>-- <br><font><span style="font-family:arial,helvetica,sans-serif">Akiko Ikkai, Ph.D. <br>Postdoctoral Fellow<br style="font-family:arial,helvetica,sans-serif"></span></font><font style="font-family:arial,helvetica,sans-serif" face="'PrimaSans BT,Verdana,sans-serif'" size="2">Department of
Psychological and Brain Sciences<br>Johns Hopkins University<br>Ames
Hall, 3400 N. Charles St.<br>Baltimore, MD 21218</font><br style="font-family:arial,helvetica,sans-serif"><br><br>
</div>