They are calculated the same way as the canonical hrf, derivatives, etc. 

The regressor is formed by making the mean of the parametric term  0 and multiplying by the hrf or derivative.

Best Regards, Donald McLaren
=================
D.G. McLaren, Ph.D.
Postdoctoral Research Fellow, GRECC, Bedford VA
Research Fellow, Department of Neurology, Massachusetts General Hospital and Harvard Medical School
Office: (773) 406-2464
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On Thu, Mar 3, 2011 at 9:13 AM, Artur P. <[log in to unmask]> wrote:
Hi all,


Could anyone point me to the specific parts of SPM 8 code that are related to parametric modulation? I'm mostly interested in how the statistics are calculated.

Also, is there any difference between SPM versions in this matter?


Any help would be much appreciated.

Kind regards,

Art