Hi
the third entry corresponds to the amplitude of the stimulus - you
might want to use this to encode different levels of assumed response
strength or measured strength of some secondary recording (say you've
got some pain paradigm where you also record perceived pain intensity
per trial)
Wrt your last question: if your TR is of the order of 3 sec and you
include the temporal derivative in the design then this is really not
important.
cheers
christian
On 15 Oct 2004, at 22:51, Scott Hayes wrote:
> Hi,
> It's not clear to me what the 3rd column represents in the custom 3
> column
> format specification of the EVs. From the manual, I see that "the
> third number
> is the value of the input during that period." I've searched the
> archives, and
> I've seen examples in which a value of '1' or '100' is used, but I was
> not able
> to find an example in which values in the 3rd column varied within an
> EV or
> across EVs.
>
> My experiment is a jittered event-related memory study w/ 5
> conditions. I
> suspect that I would enter the same input value (in the 3rd column)
> for each
> trial within and across EVs. Is this correct? And if not, under what
> circumstances would one consider varying this value?
>
> Finally, my stimulus presentation duration is 3 seconds, but the
> memory decision
> takes, on average, approximately 2 seconds. Would it be more
> appropriate to
> base the duration (value in the second column) on the subjects
> reaction time (2
> sec), as opposed to the duration of stimulus presentation (3 sec)? Or
> maybe
> this isn't a concern if temporal derivatives are added?
>
> Any suggestions or advice would be greatly appreciated.
>
> Thanks in advance,
>
> Scott
>
>
>
> *******************************
> Scott M. Hayes, M.A.
> Doctoral Student
> Clinical Neuropsychology
> Cognition & Neuroimaging Lab
> Dept. of Psychology
> University of Arizona
> Tucson, AZ
>
>
--
Christian F. Beckmann
Oxford University Centre for Functional
Magnetic Resonance Imaging of the Brain,
John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
Email: [log in to unmask] - http://www.fmrib.ox.ac.uk/~beckmann/
Phone: +44(0)1865 222782 Fax: +44(0)1865 222717
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