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

[Cheung, Shirley]

Thanks Cécile,

Yes I would like a copy of the paper when it is ready. My participants are 11 mo infants and adults. Both groups show inversion in different conditions, but mainly during the alternating & silence blocks.

I present 3 languages (English, Mandarin, Hindi) in my design. Each language is presented in the following block order: Baseline (non-alternating word), directly followed by a Test (alternating phonemic contrast), and ending with a Silence period. Then, the next language is presented. The 3 languages rotate in an orderly fashion for at least 5 repetitions.

Thank you Maheen, Felix, and Erika for the references!


Shirley Cheung
Leverhulme Trust Doctoral Scholar
Department of Psychology
Lancaster University, U.K.

On 24 Feb 2017, at 11:01, Cecile Issard <cecile.issard at etu.parisdescartes.fr<mailto:cecile.issard at etu.parisdescartes.fr>> wrote:

Hi Shirley,

Very good question… but no one has an answer. I am about to submit a paper with Judit Gervain (my advisor) exactly on that, maybe I can send you a preprint we it is submitted ? What’s your design exactly ?

Best,

Cécile
Le 23 févr. 2017 à 13:25, Cheung, Shirley <s.cheung at lancaster.ac.uk<mailto:s.cheung at lancaster.ac.uk>> a écrit :

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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Cécile Issard
Doctorante
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