<p dir="ltr">Many thanks!</p>
<br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Wed, 17 Dec 2025, 15:40 ivano triggiani, <<a href="mailto:ivanotriggiani@gmail.com">ivanotriggiani@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div>Let's see...</div><div>If you use pwelch per x,y, and z, you are basically calculating the power spectrum (which is related to the squared magnitude of the Fourier transform), so I doubt it's correct to square them again. </div><div>I know somebody uses the average, which is a possibility, but it can underestimate the total spectrum.</div><div>The correct solution (again, it can look weird) should technically be the sum of the 3 PSDs, which are already squared, so Ptot(f)=Px(f)+Py(f)+Pz(f) is the vector sum and should be the correct solution.</div><div><br></div><div>Everyone feels free to correct me if I am wrong.</div><div><br></div><div>Ciao,</div><div><br></div><div>Ivano</div><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div>---</div><div><br></div><div><b><font face="arial black, sans-serif">A. Ivano Triggiani, Ph.D.</font></b></div><div><p class="MsoNormal" style="margin:0in;font-size:11pt;font-family:Calibri,sans-serif;color:rgb(0,0,0)"><br></p></div><div>________________________________________________<br><br></div></div></div></div><br></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Dec 17, 2025 at 6:50 AM Fabio Strappazzon <<a href="mailto:fab.strappaz@gmail.com" target="_blank" rel="noreferrer">fab.strappaz@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">Ciao Ivano,<div>thank you for your anwer.</div><div><br></div><div>1) As expected, thanks.</div><div><br></div><div>2) Your solution would be fine but the problem is that for each dipole I have a 3 x pnts array (orientation x time points) and I do not know how FieldTrip would take care of that. But even trying to using classical MATLAB function like pwelch (as I'm curretly doing) I'm not super sure how should I proceed: should I calculate a separate PSD for orientation? And then what: summing across orientation? Taking the average? Taking the squared root of sum?</div><div><br></div><div>Thank you for your help</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Il giorno mar 16 dic 2025 alle ore 22:44 ivano triggiani <<a href="mailto:ivanotriggiani@gmail.com" target="_blank" rel="noreferrer">ivanotriggiani@gmail.com</a>> ha scritto:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><p style="font-family:"Google Sans Text",sans-serif;line-height:1.15;margin-top:0px">Caro Fabio,</p><p style="font-family:"Google Sans Text",sans-serif;line-height:1.15;margin-top:0px">My humble opinion:</p><p style="line-height:1.15;margin-top:0px"><font face="Google Sans Text, sans-serif">1. Since source reconstruction is a well-known </font>ill-posed problem, every method relies on different constraints. For instance, MNE minimizes the overall L2 norm, which often results in smooth solutions, easily distorted if noise is significant.<br><br>To stabilize the solution, regularization methods use, for example, estimation of the noise covariance and a regularization parameter. This scaling process changes the output, which is no longer strictly measured in physical units (like current density) but is reported in a.u. or normalized quantity. sLORETA and eLORETA operate under a similar concept of weighted or standardized normalization (I am simplifying!).<br><br>2. I think so, but you must calculate the PSD on the estimated source time series. For distributed solutions the data is contained in the source.avg.mom field, not source.avg.pow, if I remember correctly.<br>You need to restructure the source.avg.mom field so that FieldTrip treats each source location as a separate "channel" before running ft_freqanalysis.<br>Something like:<br><br>cfg = [];<br>cfg.method = 'mtmfft'; % or whatever<br>cfg.output = 'pow';<br>cfg.foi = 0.5:0.5:40; % freqs<br>freq_source = ft_freqanalysis(cfg, source_data);<br><br>The resulting PSD may look "weird" compared to sensor-level data because the spatial filter (source method) affects the spectral profile of the noise and signal.</p></div><div><div><div dir="ltr" class="gmail_signature"><div dir="ltr"><div>Ciao,</div><div><br></div><div>Ivano</div><div><br></div><div>---</div><div><br></div><div><b><font face="arial black, sans-serif">A. Ivano Triggiani, Ph.D.</font></b></div><div><p class="MsoNormal" style="margin:0in;font-size:11pt;font-family:Calibri,sans-serif;color:rgb(0,0,0)"><br></p></div><div>________________________________________________<br><br></div></div></div></div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Tue, Dec 16, 2025 at 11:55 AM Fabio Strappazzon via fieldtrip <<a href="mailto:fieldtrip@science.ru.nl" target="_blank" rel="noreferrer">fieldtrip@science.ru.nl</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>Dear all,</div><div><br></div><div>I'm currently using wMNE as inverse operator. </div><div>I would like to know two things:</div><div><br></div><div>1) What are the units of measure of source reconstructed activity? I see that many papers report them as arbitrary units (a.u.) but I would like to know more why is that the case.</div><div><br></div><div><div>2) Would it be possible to still apply the FieldTrip functions for calculating PSDs (ft_freqanalysis) on outputs from source recontructed data with distributed apporaches (like MNE) or there are some specific functions for those kind of data? If so, on which outputs are calculated: on the source.avg.mom or the source.avg.pow?</div><div><br></div><div>Many thanks,</div><div><br></div></div><span class="gmail_signature_prefix">-- </span><br><div dir="ltr" class="gmail_signature"><div dir="ltr"><i><font face="georgia, serif">Strappazzon Fabio, </font></i><div><i><font face="georgia, serif">PhD Student at ITAB (Institute for Advanced Biomedical Technologies) - Chieti</font></i></div></div></div></div>
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