Can you give any more information on your acquisition, then? What is your TE, TR, flip angle, etc.? Have you tried plotting the time series of some voxels in a region that you believe a priori should produce strong results? e.g. if you have a task with faces, why not look at V1. You may also want to create a contrast that is simply "faces > fixation". That *should* produce strong activation in visual cortex. Although, that will also depend on your design.

________________________________________
From: SPM (Statistical Parametric Mapping) [[log in to unmask]] on behalf of Geon-Ho Jahng [[log in to unmask]]
Sent: Thursday, March 21, 2013 10:57 PM
To: [log in to unmask]
Subject: Re: [SPM] the error message during the Model estimation

Dear Cyril and Satoru

Thanks Cyril for recommendation. We rechecked several times of the pre-processed images and the statistical model. I have used SPM almost 10 years.
The problem may be related to our imaging technique. In this fMRI study, we did not use BOLD EPI, but use a gradient-echo sequence with a short-echo time. The regular processing steps for BOLD images may do not work for the gradient-echo images. Sensitivity of activation may too low in the gradient-echo images compared to the BOLD images.

I would like to hear from experts to improve sensitivity to detect activation. Is it better if I use any non-parametric methods in the statistical modeling rather than the general linear model?

Best regards
Geon-Ho

On Mon, Mar 18, 2013 at 8:41 PM, cyril pernet <[log in to unmask]<mailto:[log in to unmask]>> wrote:
Geon-Ho,

During parameters estimation, SPM runs a omnibus F-test to find where there is some activation .. and it obviously failed to find any ('There are no significant voxels.')
This can be attributed to several things. (1) there is truly no signal (unlikely) (2) SNR is particularly bad (less unlikely but very rare) (3) preprocessing and/or model specification are incorrect (more likely)

so things to do: check 1st that your images are well realigned and if normalization was performed, check your segmented images (check reg T1 and segments) and the resulting normalized images (check reg template and images) - 2nd review the design matrix, and regressors - 3rd if steps 1 and 2 tells you all seems ok, run some diagnostic tools (see spm extensions) - those steps are likely to spot some problems and resolve your issue

Good luck
Cyril

Dear SPM Experts,

We process the following data with SPM5.
We scanned 72 dynamics with the face-name association task of the two-repeated fixation-novel-fixation-control stimulation.
In each subject, we are interested in investigating the following contrasts:
fixation < novel and fixation < control
fixation > novel and fixation > control
novel < control and novel > control.

We get the following error message during the Model estimation step:

Error Dialog:
Please check your data. There are no significant voxels. The globals are plotted for diagnosis.


In the MatLab window

Error running job: Error using spm_spm (line 861)

Please check your data: There are no significant voxels.

In file "C:\SPM\spm5\spm_spm.m" (v3055), function "spm_spm" at line 861.

In file "C:\SPM\spm5\spm_config_fmri_est.m" (v832), function "run_est" at line 394.

Please help us figure out the error message.
Best regards

Geon-Ho

--
Geon-Ho Jahng,Ph.D.
Professor of Radiology
Kyung Hee University Hospital at Gangdong
School of Medicine, Kyung-Hee University
149 Sangil-dong, Gangdong-gu,
Seoul 134-727 South Korea
TEL: 82-2-440-6187
FAX:82-2-440-6932
Email: [log in to unmask]<mailto:[log in to unmask]>



--
Dr Cyril Pernet,

Academic Fellow
Brain Research Imaging Center
http://www.bric.ed.ac.uk/
Division of Clinical Neurosciences
University of Edinburgh
Western General Hospital
Crewe Road
Edinburgh
EH4 2XU
Scotland, UK

[log in to unmask]<mailto:[log in to unmask]>
tel: +44(0)1315373661
http://www.sbirc.ed.ac.uk/LCL/
http://www.sbirc.ed.ac.uk/cyril



The University of Edinburgh is a charitable body, registered in
Scotland, with registration number SC005336.




--
Geon-Ho Jahng,Ph.D.
Professor of Radiology
Kyung Hee University Hospital at Gangdong
School of Medicine, Kyung-Hee University
149 Sangil-dong, Gangdong-gu,
Seoul 134-727 South Korea
TEL: 82-2-440-6187
FAX:82-2-440-6932
Email: [log in to unmask]<mailto:[log in to unmask]>