[Homer-users] HRF inversion...any explanations?

[Erika Molteni]

DEAR SHIRLEY,
I hope that the paper enclosed will help.
Regards,
Erika

On Thu, Feb 23, 2017 at 12:25 PM, Cheung, Shirley <s.cheung at lancaster.ac.uk>
wrote:

> Dear Homer2 community,
>
> I’m experiencing some difficulty interpreting my results in Homer2. In
> some conditions (but not all), my HRFs are inverted where HbR is higher
> than HbO. My experimental procedure consists of short auditory stimuli
> presented in a repeated Baseline (non-alternating), Test (alternating), and
> Silence block order. Does anyone have an idea why HRF inversion occurs?
> Could it be due to the experimental design, arrangement of
> sources/detectors, averaging baselines/blocks incorrectly, other factors
> such as watching a silent video during auditory stimulus presentation, or
> anything else?
>
> Also, is it possible to manually set a baseline interval in Homer2 that
> does not immediately precede the onset of a stimulus?
>
> Any suggestions or explanations would be greatly appreciated, thank you!
>
>
> Shirley Cheung
> Leverhulme Trust Doctoral Scholar
> Department of Psychology
> Lancaster University, U.K.
>
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