Hi Doug,
Sorry to follow this topic with a delay but we tried to model BOLD
signal undershoot with a gamma function and we failed. The problem is,
gamma function generates positive values and we can NOT use "inverse gamma
function" (or otherfunction similar to that) as a part of mkanalysis-sess
(for modeling BOLD signal undershoot). We even used matlab gammafit to
estimate parameters and it said that values should be positive otherwise
gammafit function fails.
Do you have any suggestion?
On Wed, Apr 10, 2013 at 6:46 PM, Douglas N Greve
<gr...@nmr.mgh.harvard.edu>wrote:
>
> 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, sha...@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
>>> <gr...@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
>>>> gr...@nmr.mgh.harvard.edu
>>>> Phone Number: 617-724-2358
>>>> Fax: 617-726-7422
>>>>
>>>> Bugs:
>>>> surfer.nmr.mgh.harvard.edu/****fswiki/BugReporting<http://surfer.nmr.mgh.harvard.edu/**fswiki/BugReporting>
>>>> <http://**surfer.nmr.mgh.harvard.edu/**fswiki/BugReporting<http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting>
>>>> >
>>>> FileDrop:
>>>> www.nmr.mgh.harvard.edu/****facility/filedrop/index.html<http://www.nmr.mgh.harvard.edu/**facility/filedrop/index.html>
>>>> <h**ttp://www.nmr.mgh.harvard.edu/**facility/filedrop/index.html<http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html>
>>>> >
>>>> Outgoing: ftp://surfer.nmr.mgh.harvard.***
>>>> *edu/transfer/outgoing/flat/**
>>>> greve/ <ftp://surfer.nmr.mgh.harvard.**edu/transfer/outgoing/flat/**
>>>> greve/ <ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/>
>>>> >
>>>>
>>>>
>>>>
>>>>
>>> --
>>> 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
>>> ______________________________**_________________
>>> Freesurfer mailing list
>>> Freesurfer@nmr.mgh.harvard.edu
>>> https://mail.nmr.mgh.harvard.**edu/mailman/listinfo/**freesurfer<https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer>
>>>
>>
>>
> --
> Douglas N. Greve, Ph.D.
> MGH-NMR Center
> gr...@nmr.mgh.harvard.edu
> Phone Number: 617-724-2358
> Fax: 617-726-7422
>
> Bugs:
> surfer.nmr.mgh.harvard.edu/**fswiki/BugReporting<http://surfer.nmr.mgh.harvard.edu/fswiki/BugReporting>
> FileDrop:
> www.nmr.mgh.harvard.edu/**facility/filedrop/index.html<http://www.nmr.mgh.harvard.edu/facility/filedrop/index.html>
> Outgoing: ftp://surfer.nmr.mgh.harvard.**edu/transfer/outgoing/flat/**
> greve/ <ftp://surfer.nmr.mgh.harvard.edu/transfer/outgoing/flat/greve/>
>
>
>
--
Shahin Nasr
PhD in Cognitive Neuroscience
Martinos Imaging Center, MGH
Harvard Medical School
_______________________________________________
Freesurfer mailing list
Freesurfer@nmr.mgh.harvard.edu
https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
The information in this e-mail is intended only for the person to whom it is
addressed. If you believe this e-mail was sent to you in error and the e-mail
contains patient information, please contact the Partners Compliance HelpLine at
http://www.partners.org/complianceline . If the e-mail was sent to you in error
but does not contain patient information, please contact the sender and properly
dispose of the e-mail.
