[Homer-users] Cutoff value to remove high frequency noise

[Lily]

Dear Meryem,

Thank you for your response.

(It seems that there was a delay in the system that until today I received
your email).

Yes, I see a peak around 1Hz in frequency domain. However, as the true
response is unknown, my question is thus if there is hemodynamic response
which occurs in the range from 0.5 to 1.5 Hz or higher, then in that case
we have the risk of removing it too ? I am sorry to ask this but I have no
background in neuroscience.

Best regards,
Hue.

On 25 July 2016 at 17:32, Meryem Ayse Yucel <mayucel at nmr.mgh.harvard.edu>
wrote:

> Hi Hue,
>
> This value is chosen to remove heart beat (which is ~1Hz, test this by
> looking at your data for hearbeat with and without lpf) and instrumental
> noise available in the data. You can use lower values, but that has the
> risk of removing the hemodynamic response itself.
>
> Meryem
>
>
> > Dear all,
> >
> > I would like to ask about the cutoff value to remove high frequency noise
> > in fNIRS data.
> >
> > In recent papers (Brigadoi et al (2014) Motion artifacts in functional
> > near-infrared spectroscopy A comparison of motion correction techniques
> > applied to real cognitive data, Yucel (2014) Targeted principle component
> > analysis - a new motion artifact correction approach for near-infrared
> > spectroscopy, ...) the authors used 0.5 Hz as cutoff value for the
> lowpass
> > filter and there was no reference or explanation about that value.
> >
> > I do not understand why 0.5 was chosen. Could you help me on this?
> >
> > Thank you very much in advance for your response.
> >
> > Kind regards,
> > Hue.
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