[Homer-users] Odd HRF shape: possible explanations?

[Sergio Novi]

Dear Luca , it is a little hard to say something without seeing your HRFs,
but it might be related with motion artefacts. Have you removed motion
artefacts in your data analysis? I have analyzed some data from newborns
and the presence of motion is too high.

Best,
Sergio Novi

On Fri, Mar 10, 2017, 12:50 Luca Filippin <luca.filippin at gmail.com> wrote:

> Hi,
>    we've been using Homer2 to analyze some data collected on newborns and
> we get some puzzling HRF shapes as result, averaged over a 40 secs temporal
> window The function has in some cases multiple humps: it rises then
> descends a bit and then rises again, descends again and so on, 2 or more
> times. In some other cases it simply rises and doesn't fall at all.
>
> Would you have any explanations for that?
>
> We believe that it has something to do with the stimuli design.
>
> Our stimuli are sounds of variable length between 18 and 22 secs, roughly.
> Each sound is made of block of N repeated short sound segments (for
> example: BI), interleaved with other blocks of M sound segments of the same
> type BI, but shorter duration:
>
> N x BI (pause) M x shorter BI  (variable pause) N x BI (variable pause) M
> x shorter BI  (variable pause) ...
>
> where "variable pause" is a silent segment of duration between 50 and 80
> ms.
>
> We wonder if  there's a way to do the analysis so to disentagle the
> contribution of each block of sound segment within a sound stimulus. We
> play different sounds during the experiments: each sounds onset is
> separated by roughly 50 seconds. The problem would be perhaps, the
> estimation of the baseline.
>
> Many thanks for your help,
> Luca
>
>
>
>
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