Hi Wang,
The PSDMax must be long enough so that the window captures the entire
response to your event. As you mention, the SPM HRF is 32 sec long, but
this is the response to a brief (ie, ~1TR) stimulus (ie, it's an impulse
response). If your stimulus is longer, then SPM will convolve the HRF
with it to create a response which is longer than 32 sec. The PSDMax
must be set long enough to capture this full response. As a rule of
thumb, you can set PSDMax to the stimulus duration + 32.
doug
ps. I don't monitor this list, so please send any responses to me directly.
Date: Thu, 16 Feb 2006 21:47:48 +0800
From: Wang Ling <[log in to unmask]>
To: [log in to unmask]
Subject: [SPM] A question on optseq2
Dear Experts,
Could anyone please tell me how to correctly set the parameter psdwin
when using optseq2. Does the PSDMax minus mean the duration of HRF?
For example, if the duration of HRF is 32(in SPM), which is used to
convolute,
I would set PSDMin to 0 and set PSDMax to 32. Is it correct?
Thanks for your help!
--
Wang Ling
--
Douglas N. Greve, Ph.D.
MGH-NMR Center
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Phone Number: 617-724-2358
Fax: 617-726-7422
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