<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hi Sara. Unless you care about frequencies per se, epoching and baseline-correcting the data won't be a problem. From a time-domain perspective, this won't change anything.<div><br></div><div>BTW, someone else suggested using the 1-Hz high-pass cutoff, performing ICA, and then applying the component coefficients to the unfiltered data. That sounds like a great suggestion, although I don't know if there is a technical reason why it wouldn't work. Does anyone out there know if there would be a problem with this?</div><div><br></div><div>Steve</div><div><br></div><div>ps- The email trail on this topic has gotten out of hand, so I deleted everything except the most recent message and your original message.</div><div><br><div><div>On Oct 13, 2011, at 7:20 AM, Sara Graziadio wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div>Steve,<br>actually I was refering to your book when I was writing that the filter would deforme/reduce the erp. But following David Groppe's suggestion would mean to reduce activity at different frequency all across the spectrum, wihtout exactly knowing which frequencies I am reducing, am I right? If I want to look at the psd as well as at the erps, would this analysis just be correct? I am always concerned about applying data modification that I cannot fully control..if you know what I mean...<br>Thank you very much<br>Best<br><br>Sara<br></div></blockquote></div><div><br></div><blockquote type="cite">On Wed, Oct 5, 2011 at 10:46 AM, Sara Graziadio<br><<a href="mailto:sara.graziadio@newcastle.ac.uk">sara.graziadio@newcastle.ac.uk</a>> wrote:<br>Hello,<br>I would like just a suggestion about some data cleaning/analysis I am doing. I<br>am doing an ERP analysis and I want to clean my data first with the ICA. In<br>theory, though, I should not use an high-pass cutoff higher than 0.1 Hz to not<br>reduce the erp amplitude. On the other side the ICA does not work well if the<br>high-pass cutoff is lower than 0.5 Hz...what is then the best method to apply?<br>Has anybody tested how robust the ica is with a 0.1Hz filter?<br>I have also another question: I am doing the analysis on 94 electrodes<br>referenced to Fz. I planned to average reference the data but actually there is<br>quite a large spread of noise on all the electrodes with this method (muscular<br>artefacts for example from the temporal electrodes). But actually almost all<br>the papers are using the average reference so I was surprised, am I the only<br>one having this problem of noise? Would not be better just to keep the Fz<br>reference and then perhaps to average the erps for every different cortical<br>area and do the analysis on these averaged erps?<br><br>Thank you very much<br><br>Best wishes<br><br>Sara Graziadio<br>Research Associate<br>Newcastle University<br></blockquote><br><div>
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