Andy,
The temporal derivative can correct for two different unknowns in the
experiment. The first is the exact timings of the neural reponse to
the experiment - which you apparently have no problems with as you have the
video recordings. The second is the (usually) unknown delay (or time to
peak) of the HRF.
Hence you should leave in the temporal derivative to allow the reponse fit
to adapt to the unknown delay of the HRF.
Cheers, Mark.
Mark Woolrich.
Oxford University Centre for Functional MRI of the Brain (FMRIB),
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK.
Work: +44-(0)-1865-222713, Mobile: +44-(0)-7808-727745
Email: [log in to unmask]
On Thu, 23 Jan 2003, Andy Goldfine wrote:
> In my event-related design I am able to record the subjects' actions to
> 0.1 seconds with video taping. Since the event time is known
> accurately, is using the temporal derivative recommended?
>
> Thanks.
>
|