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Hi Donald, I'm coming back to this, just want to clarify something.. I mentioned (in my email above), that improvements in performance across time reflect decreases in neural activity (in a one-sample t-test). Then, I go on to show that the slope of this relationship (between performance and neural activity) is different in younger and older adults. I'm wondering, since I show deactivations related to improvements in performance in the one-sample t-test, is this also the case for the two-sample t-test comparing young and older adults? Can I say that the slope of the relationship between performance and specifically neural DEACTIVATIONS (since I show de*activations* in the one-sample, not activations), is different by age? Thanks, Joelle On Fri, Apr 15, 2016 at 1:47 PM, MCLAREN, Donald <[log in to unmask]> wrote: > You can test if their slopes are different. The t-test you did was for the > slope of the PM. You just can't use the phrase "closeness" as you are > testing the slope. > > Best Regards, > Donald McLaren, PhD > > > On Fri, Apr 15, 2016 at 10:52 AM, Joelle Zimmermann < > [log in to unmask]> wrote: > >> Hi Donald, >> >> Thanks for your help. Could you please clarify your second point? >> >> Additionally, I conduct a 2-sample t-test, forwarding the first-level PM >>> contrasts to the second-level, comparing young and old subjects. Here I >>> find young>old gives me some interesting task-related regions. Am I correct >>> to say that young adults' neural activations are more closely tied to >>> behavioral performance than for old adults? >>> >> >> No. You can say that the slope of the relationship is different, but you >> can't conclude that the relationship is stronger as you only have the slope >> at the group level. >> >> Is there a (another?) way to test differences between young and old >> subjects in terms of how their behavior performance (parametric modulator) >> modulates to their neural activations? >> >> Thanks, >> Joelle >> >> On Thu, Apr 14, 2016 at 8:11 PM, MCLAREN, Donald < >> [log in to unmask]> wrote: >> >>> See below. >>> >>> Best Regards, >>> Donald McLaren, PhD >>> >>> >>> On Thu, Apr 14, 2016 at 4:36 PM, Joelle Zimmermann < >>> [log in to unmask]> wrote: >>> >>>> Hi SPMers, >>>> >>>> I am looking at the relationship between neural activity and behavioral >>>> performance, and was hoping for some insight for correct interpretation of >>>> a particular analysis. >>>> >>>> On the first level, I have a model with my fMRI signal (first column), >>>> my behavioral performance as a parametric modulator (second column), and my >>>> 6 motion regressors. I am interested in the behavioral parametric >>>> modulator, so I put a contrast over the second column. >>>> >>>> When I forward these individual subject contrasts to the second level, >>>> and do a one-sample t-test to look at group, with t-contrast [-1], I find >>>> certain task-related regions show significance. Would it be correct to say >>>> that the behavioral performance modulates neural activity, with >>>> improvements in performance across time reflecting decreases in neural >>>> activity in these certain regions? >>>> >>> >>> Yes. >>> >>> >>>> >>>> Additionally, I conduct a 2-sample t-test, forwarding the first-level >>>> PM contrasts to the second-level, comparing young and old subjects. Here I >>>> find young>old gives me some interesting task-related regions. Am I correct >>>> to say that young adults' neural activations are more closely tied to >>>> behavioral performance than for old adults? >>>> >>> >>> No. You can say that the slope of the relationship is different, but you >>> can't conclude that the relationship is stronger as you only have the slope >>> at the group level. >>> >>> >>>> >>>> Thanks in advance, >>>> Joelle >>>> >>> >>> >> >