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In my understanding parametric modulation gives you areas with significant correlation (positive or negative) of BOLD and your modulator - so I am not sure if you can say that attention is modulating PFC activity - it might be also that PFC activity modulates attention. Regards Marek W dniu 2016-08-15 o 16:32, Colin Hawco pisze: > In regards to1) > > If you do a one-sample t-test on the parametric modulator column, yes, this shows regions in which the change in BOLD signal as related to (modulated by) the attention score you input. > > As a side note, p-mods are orthogonal to the HRF/task effects, so you can find activity realted to the p-mod in regions which do not show overall task effects. > > In regards to 2), the correct interpretation is: > During the decision process, the trial-by-trial attentional modulation effect on putamen activity was correlated with subject's age. > > Good luck! > > Colin Hawco, PhD > Neuranalysis Consulting > Neuroimaging analysis and consultation > www.neuranalysis.com > [log in to unmask] > > > > -----Original Message----- > From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] On Behalf Of Mike > Sent: August-13-16 6:22 AM > To: [log in to unmask] > Subject: [SPM] Interpretation of parametric modulation > > Hi, > > I have two questions regarding parametric modulation. > (1) My first-level model had 3EVs. I added a parametric modulator (attention level) in one of these EVs (i.e., the regressor of interest), which corresponds to the trial-by-trial attention level during the decision period. If I use contrast 1 for this parametric regressor in the second-level analysis (one-sample t test in SPM) and identified that prefrontal cortex (PFC) was significant, that means PFC activity is parametrically modulated by subject's trial-by-trial attention level during the decision process. Is this correct? > > (2) Following (1). I totally have 20 subjects. In the second-level analysis (using the first-level t contrast of the parametric regressor, not the first-level t contrast of the EV itself) described in (1), I entered each subject's age as a covariate. Then I used contrast 1 to search for positive correlation with age and I identified putamen. What is the correct interpretation? (A) During the decision process, putamen activity is not only modulated by trial-by-trial attention but also correlated with subject's age; (B) During the decision process, the trial-by-trial attentional modulation effect on putamen activity was correlated with subject's age. > > Thanks. Mike -- Marek Wypych PhD Laboratory of Brain Imaging (LOBI) Neurobiology Center Nencki Institute of Experimental Biology Pasteur 3, 02-093 Warsaw, Poland Tel.: +48 22 5892 550 http://lobi.nencki.gov.pl/