[FieldTrip] EEG preprocessing

[David Groppe]

You need to low-pass filter the data before downsaple to avoid aliasing.
The matlab function decimate.m can do this for you.
   cheers,
     -David

On Thu, Jan 10, 2013 at 3:22 PM, Narayan Iyer <eeguser at hotmail.com> wrote:
> Hi
>
> I have a question on EEG preprocessing. The sampling rate of my 64 channel
> EEG data is 500 Hz and I would like to down-sample this to 256 Hz or 128 Hz.
> My question is, i it advisable to low-pass filter the data first (70 Hz) and
> then down-sample  followed by high-pass filter (0.5 Hz) to avoid aliasing
> effect  or should I down-sample first and then band-pass filter the data
> (0.5-70 Hz) ? Or does the sequence really matter ?
> I am new to EEG data analysis so this question might be really basic, but
> any help is highly appreciated!
>
> Thanks
> Subbu
>
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-- 
David Groppe, Ph.D.
Postdoctoral Researcher
North Shore LIJ Health System
New Hyde Park, New York
http://www.cogsci.ucsd.edu/~dgroppe/