Sorry that I keep on asking questions but I want to know if using a model can significantly increase the chance of getting a significant response.
As far as I see for the positive peak, when I use a model (e.g. gamma model or spmhrf), I see a more significant response compared to when I use the FIR model. Is it correct? If true, then the same might be correct for the negative peak.
P.S.: To be more clear, I am talking about the response maps relative to the baseline.
yes, that is what you want. The only other way that comes to mind is to model each event type as two event types one delayed relative to the other. Then model the responseto each as a gamma. If the delay is right, then the first gamma should model the main positive response and the second gamma will model the negative response. both will be independent from the other.
doug
On 04/10/2013 05:00 PM, shahin@nmr.mgh.harvard.edu wrote:
I think I figured it out but I want to double check. I am generating
group-average map for my subjects using isxconcat-sess command which
generates ces maps for each time frame. I think these maps are what I
wanted. Right?
If you still have other solutions that you think may generate more
reliable results, I am eager to know. For instance, is there anyway to
fit a model as we do for spmhrf or fslhrf, but just for the negative
peak?
Regards
That's the problem Doug. I have already generated the FIR model but how
can
I show the sig MAP for one "particulat time point". What are the other
ways?
On Wed, Apr 10, 2013 at 4:05 PM, Douglas N Greve
<greve@nmr.mgh.harvard.edu>wrote:
Hi Shahin, there are several ways that you could do it. The one that
immediately comes to mind is to use an FIR and then test for a
difference
at a particular post stimulus time point.
doug
On 04/10/2013 03:54 PM, SHAHIN NASR wrote:
Hi,--
I want to generate a map to show the significant difference
between
HRF undershoot (negative peak of activity) between two conditions
independent from the positive peak. Is there anyway, to generate this
map?
P.S.: Please note that I need a map and not a time course graph.
--
Shahin Nasr
PhD in Cognitive Neuroscience
Martinos Imaging Center, MGH
Harvard Medical School
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu
Phone Number: 617-724-2358
Fax: 617-726-7422
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--
Shahin Nasr
PhD in Cognitive Neuroscience
Martinos Imaging Center, MGH
Harvard Medical School
--
Shahin Nasr
PhD in Cognitive Neuroscience
Martinos Imaging Center, MGH
Harvard Medical School
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--
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu
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