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Thanks Donald :) On Mon, Apr 18, 2016 at 8:05 PM, MCLAREN, Donald <[log in to unmask]> wrote: > See in line responses below. > > Best Regards, > Donald McLaren, PhD > > > On Mon, Apr 18, 2016 at 7:09 PM, Joelle Zimmermann < > [log in to unmask]> wrote: > >> 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). >> > > This was related to the -1 that you used at the first level. > > >> >> 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? >> > > You didn't show deactivations are related to improvements. All you have > shown is a negative relationship. This shouldn't be confused with activity > below baseline. > > In the two sample test, you are comparing the negative slopes. If Y>O, > then the negative slope is greater (more negative) in young compared to > old. > > > > >> >> 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? >> > > No. You are looking at the slope. The slope does not tell you anything > about the activations or deactivations relative to baseline. > > > >> >> 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 >>>>>> >>>>> >>>>> >>>> >>> >> >