Dear SPMers,
I am interested in inter-hemispheric differences in processing of different stimuli – I therefore flipped my functional images along the midsagittal plane (after normalization to a symmetrical MNI template and smoothing) and included the images as two runs (one run unflipped and second run same images flipped) in the first-level design. When I compare one unflipped contrast with the same contrast flipped, activation is not exactly mirrored (peak intensities and coordinates differ slightly). Does anyone have an idea why that is the case? Shouldn’t the unflipped and flipped contrast be exactly the same, just flipped? And is it correct to include both sets of images in one model, as different runs?
Thanks in advance,
Kerstin
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