The inclusion of the temporal or dispersion derivatives captures variance in the response in the cases where neural activity is shift in time of onset or duration. You can think of this as capturing more of the signal in the data.
The inclusion of motion parameters is to account for shifts in signal due to motion. You can think of this as reducing the noise in the data.
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 Sun, Jan 2, 2011 at 4:45 PM, Claire (Jung Eun) Han
<[log in to unmask]> wrote:
Hello,
This question is regarding the first model specification.
Is it preferred to choose HRF only (without time or/and dispersion derivatives) when we add realignment parameters as multiple regressors? If so, why?
Thanks,
Claire