[VoxBo] PSC in FIR models

[Russell Epstein]

Hi all,

I have a simple question about FIR models and percent signal change.
It is my understanding that if one mean-norms one's data, then
multiplying the beta values by 100 gives you percent signal change.  I
presume that this is true for both FIR and "regular" models (i.e.
models in which the regressors are involved by the standard
hemodynamic response function).  So I would expect that the peak
response obtained by an FIR model, when expressed as percent signal
change, would be somewhat similar to the PSC obtained from and
HRF-convolved model.

But, when I go back and look at results from an earlier study (rapid
event-related, in case that matters) I find that FIR peak is about
0.7%, but the beta values for the normal model translate into 3-4%.
How is is possible?

The only thing I can think that might be relevant is that the
HRF-convolved model included first and second derivatives, but it's
hard to see how that would make for such a difference.

Thanks for any insight!

Russell