Hello,

I'm analyzing retinotopy data.

I used expanding ring and rotating wedge. For my pilot, unfortunately, we used only 2 cycles for each stimulus and 1 cycle lasted 200 seconds (for sure I will change to more cycles lasting less). TR = 2.5.

Retinotopy paradigm files are as follow:

-for expanding ring (pos direction since it expands):

stimtype eccen
direction pos

-for rotating wedge (neg direction since is counter-clockwise):

stimtype polar

direction neg

To compute analyses, I ran the following pipeline:

1) recon-all

2) preproc-sess

3) mkanalysis-sess

4) selxavg3-sess

Having only two cycles for each stimulus, in mkanalysis-sess, I used the option -hpf and lowered the filter to 0.5.

In the last level (selxavg3-sess), I get the error.

Basically this step runs up to when MATLAB starts to calculate. Here I get the following error:

MATLAB is selecting SOFTWARE OPENGL rendering.
                            < M A T L A B (R) >
                  Copyright 1984-2019 The MathWorks, Inc.
              R2019b Update 3 (9.7.0.1261785) 64-bit (glnxa64)
                             November 27, 2019
 
To get started, type doc.
For product information, visit www.mathworks.com.
 
>> >> >> >> /usr/local/freesurfer/fsfast/toolbox/fast_selxavg3.m
>> /usr/local/freesurfer/fsfast/toolbox/fast_ldanaflac.m
>> /usr/local/freesurfer/matlab/MRIread.m
>> >> >> starting fast_selxavg3b

#@# SUBJ02 ###############################
/media/sf_w_Desktop/w_pRF/retinotopy/SUBJ02
-------------------------
$Id: fast_selxavg3b.m,v 1.4 2016/05/04 22:16:47 greve Exp $
-------------------------
outtop = /media/sf_w_Desktop/w_pRF/retinotopy
Extension format = nii.gz
INFO: key nSliceGroups unrecognized, line 11, skipping
nruns = 2
autostimdur =


outanadir = /media/sf_w_Desktop/w_pRF/retinotopy/SUBJ02/bold/retinotopy.lh
Found 118266/125623 (94.1) voxels in mask 1
Creating Design Matrix
 ... creation time =  0.008 sec
DoMCFit = 1
ntptot = 260, nX = 158, DOF = 102
Saving X matrix to /media/sf_w_Desktop/w_pRF/retinotopy/SUBJ02/bold/retinotopy.lh/Xtmp.mat
XCond = 6.85663e+16 (normalized)
ERROR: design is ill-conditioned
ans =
     1
>> ------------------------------------------
ERROR: fast_selxavg3() failed\n

I'm stuck with analyses and I cannot proceed further. 

Could you provide some insight on what to do? Having only two long lasting cycles, do I have to use further optional flags in my commands?

Thank you for your time,

Marco

--

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Marco Ninghetto, PhD candidate
Laboratory of Neuroplasticity
Nencki Institute of Experimental Biology
Polish Academy of Sciences
3 Pasteur Street, 02-093 Warsaw, Poland