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

[Cheung, Shirley]

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.