<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>In addition to the excellent suggestions provided by others, you may want to read chapter 5 in my book (An Introduction to the Event-Related Potential Technique, 2005, MIT Press). It provides a description of how filters work in the time domain, which makes it clearer how filters may distort your data.</div><div><br></div><div>In general, it is worth keeping in mind that, for transient ERP responses, filters will always distort your data to some extent. The amount of distortion is sometimes extremely small, and the benefits of filtering may greatly outweigh these small distortions. However, the amount of distortion can be very large, leading you to wildly incorrect conclusions. To avoid this, you need to either (a) use very mild filters (wide passband and shallow slopes, or (b) really understand how filters work. If in doubt, take an artificial waveform that is similar to your data and run it through the filter. This will allow you to see how the filter is distorting the data.</div><div><br></div><div>Steve Luck</div><div><br><blockquote type="cite"><div bgcolor="#FFFFFF" text="#000000"><div class="moz-cite-prefix">On 11/18/12 9:41 AM, 诸梦妍 wrote:<br>
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<blockquote cite="mid:CADt15Uscky6Cn7q46eduJTKZkDhidOU23C_38sN5f6CKwqOaeg@mail.gmail.com" type="cite">
Dear eeglablist,
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<div>I would like to know whether there are any limitation or
rules in filtering EEG data, or if there are someone who could
recommend some papers about how high-pass filter change the
data. </div>
<div><br>
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<div>I have read some basic principles about how filter works, but
still don't know how to choose a proper High-pass parameter to
remove artifacts without distorting the data. I knew some
researchers use 0.01Hz, some would recommend 0.1, 0.5 or 1Hz
and some recommend not using High-pass filter at all. </div>
<div><br>
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<div>The thing is, I found some participants' EEG waves in my
experiments had large amount of slow drift, which could be
removed by a 0.3Hz filter. However, I don't know whether that
would distort the data greatly. What I want to observe are P300,
N400 and P600 components as well as some sustained late
negativity in ERP and also 3-70Hz in Time-Frequency domain. </div>
<div><br>
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<div><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:14px;background-color:rgb(255,255,255)">Thanks
for any information you may supply me with.</span></div>
<div><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:14px;background-color:rgb(255,255,255)"><br>
</span></div>
<div><span style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:14px;background-color:rgb(255,255,255)">Zhu
Mengyan</span></div>
<div>-- <br>
Mengyan Zhu<br>
Psychology department, Peking University<br>
Dormitory 2061, Building 48,No.5 Yiheyuan Road, Haidian
District, Beijing 100871, China <br>
E-mail: <a moz-do-not-send="true" href="mailto:bj12116@gmail.com" target="_blank">bj12116@gmail.com</a><br>
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