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

[Luca Filippin]

Hi Sergio,
   here attached (leftPad2.tiff) you find the group results over 16
selected among the best babies.
I did a simple block average to get the HRF. The full process stream which
I applied is also attached.
Even if I play around with the process stream options, I get more or less
the same shape for the HRF.

Thanks!
L.




On Sat, Mar 11, 2017 at 5:43 PM, Sergio Novi <novisl at ifi.unicamp.br> wrote:

> 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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