Dear Vladimir,
Thanks for your quick and detailed answers.

>> to set the bandpass width accurately? could somebody give me some
>> advice?

>That depends on your data and on the purpose of your analysis. In
>principle you should select the bandpass in such a way that the
>activity of interest will be included and noise will be excluded.
 yes ,the bandpass width depends on the situation , not absolute.
>> 2.which is the best processing sequences: first average then filter or first
>> filter then average? However, no matter Pic1mean+2filter or Pic1filter+2mean
>> are deformated comparing to Pic 1 mean ,which I think is not in conformity
>> with the actual situation.In my opinion,filtering should be done using a
>> zero-phase band-pass filter while spm8 not.
>In principle both are possible. I'm surprised that there is such a big
>difference between the results and it looks like the original data is
>distorted too much. SPM does use a zero-phase bandpass filter but
>perhaps for such a wide band, you should use 1Hz highpass and 100Hz
>lowpass applied sequentially rather than a bandpass. Another
>possibility that many people use especially for low-cutoff highpass
>filter is to filter continuous data before epoching to avoid edge
As you suggest,the results look pretty good  when I use  1Hz highpass and 100Hz
>lowpass.That is great!The fact is that I haven't fully understand the role of filtering.
>> 3.In theory, Pic 1 mean is the evoked respones with additive gaussian noise.
>> Pic 1mean+2wt is most similar to Pic 1 mean. So I think  Pic 1mean+2wt is
>> most closet to the realistic situation. Am I right?
>It looks quite good but you are not writing  just to advertise your
>denoising method, are you ;-) ?
>sorry for my impertinence.I don't intend to advertise my denoising method, just want to get a better results. Now ,I understand .SPM8 really does a good job,that's enough .It is no need to make changes!
Thanks again!


>> --
>> haiteng  jiang
>> Research Center for Learning Science,
>> Southeast University
>> Si Pai Lou 2 # , Nanjing, 210096, P.R.China
>> Brain Imaging  Lab
>> Email: [log in to unmask]