Dear Group,
I just wanted to briefly comment on a recent posting:
>
> >would very much appreciate some pointers. I realize that for fMRI one
> >would need to treat the drug effect as an interaction effect (i.e., how
> >does the drug treatment affect the difference between the activation
> >memory task and a reference control task?)
>
> In fact, this is true for psychopharmacological PET studies of cognitive
> function as well. Without a reference state you have no way of knowing
> whether the observed effects of the drug (relative to placebo) during your
> cognitive task are specific to the experimental cognitive state or merely
> reflect more general changes on blood flow. One of the questions I am
> invaribaly asked when giving talks about psychopharmacological imaging
> studies is how we know that the effects reflect true cognitive effects of
> the drugs, and do not merely represent effects on the underlying
> vascalature. If there are differential effects of the drug (relative to
> placebo) on your two (or more) different cognitive states it's difficult to
> continue arguing for a non-specific vascular effect.
I think it is important to keep in mind the possibility of a
pharmacologic effect on the gain of the vascular response to neural activity
changes. Such a mechanism would be manifest as an interaction of
task and pharmacologic treatment.
Sincerely,
Eric
Eric Zarahn
Columbia University
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