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

[Makoto Miyakoshi]

Dear Iman,

> Using causal filter may adversely effect the direction of information

flow in the GC analysis. It is recommended that one use a

non-causal filter (for example, finite impulse response filters) with

zero phase lag

Really? The impulse response of the non-causal FIR filter spreads in both
ways in the time domain, which means info of future events leak to past...
I thought using causal filter with minimum phase makes more sense.

Makoto

On Tue, Jun 23, 2015 at 4:29 PM, Iman Mohammad-Rezazadeh <
irezazadeh at ucdavis.edu> wrote:

>  http://journal.frontiersin.org/article/10.3389/fnhum.2015.00194/abstract
>
>
>
> Using causal filter may adversely effect the direction of information
>
> flow in the GC analysis. It is recommended that one use a
>
> non-causal filter (for example, finite impulse response filters) with
>
> zero phase lag (Mullen et al., 2012, Coben and Rezazadeh, 2015)
>
>
>
>
>
> *From:* eeglablist-bounces at sccn.ucsd.edu [mailto:
> eeglablist-bounces at sccn.ucsd.edu] *On Behalf Of *Makoto Miyakoshi
> *Sent:* Tuesday, June 23, 2015 2:07 PM
> *To:* Vito De Feo
> *Cc:* EEGLAB List
> *Subject:* 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> 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
> Swartz Center for Computational Neuroscience
> Institute for Neural Computation, University of California San Diego
>



-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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