[Eeglablist] Effect of anti-aliasing low-pass filter on connectivity analysis

[Dijk, BW van]

Dear Makato,

This depends on the connectivity measure that you wish to apply.
Phase dependent measures or cross-frequency measures are strongly influenced by filter settings
If you use those than stay away from your sampling rate
The 1/3 or ¼ of the sampling frequency as a limit –in stead of the Nyquist criterium- is more safe

Regards
Bob van Dijk

Van: eeglablist-bounces at sccn.ucsd.edu [mailto:eeglablist-bounces at sccn.ucsd.edu] Namens Makoto Miyakoshi
Verzonden: dinsdag 23 juni 2015 23:07
Aan: Vito De Feo
CC: EEGLAB List
Onderwerp: Re: [Eeglablist] Effect of anti-aliasing low-pass filter on connectivity analysis

Thank you Vito for your response. Forgive me to ask you one more question.

As the ERP handbook by Luck (or his other book) recommends, anti-aliasing should better have the margin of 4-5 times of the new sampling rate e.g. if you downsample signlas to 250 Hz, anti-aliasing low-pass at 125 Hz is the standard, but recommendation is 75 Hz or even 50 Hz. Well, I haven't tested it myself so I am not sure what bad it would do if I use 125 Hz (any comment on this, anyone?) but in this case, I guess the anti-aliasing low-pass filter does affect the subsequest connectivity analysis--am I correct (assuming that I analyze EEG up to 50 Hz)?

Makoto

On Mon, Jun 22, 2015 at 9:31 AM, Vito De Feo <vito.defeo at zmnh.uni-hamburg.de<mailto:vito.defeo at zmnh.uni-hamburg.de>> wrote:
Dear Makoto,
this will not affect the connectivity analysis if the frequency of interest are far from the Nyquist frequency. For example if you downsample to 500 Hz (Nyquist freq = 250 Hz) you will have no problem in the band 0-100 Hz.
Best
Vito

Il giorno 20/giu/2015, alle ore 00:28, Makoto Miyakoshi ha scritto:

> Dear List,
>
> If I use zero-phase low-pass filter for anti-aliasing, does it affect the subsequent connectivity analysis? I ask this because EEGLAB pop_resample() automatically applies it. If it does, is there a workaround? Should I use minimum phase causal filter for anti-aliasing?
>
> --
> Makoto Miyakoshi
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
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Makoto Miyakoshi
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