|
| 1 | +## Pre processing |
| 2 | + |
| 3 | +The (f)MRI data were pre-processed with bidspm (v2.3.0; https://github.com/cpp-lln-lab/bidspm; DOI: https://doi.org/10.5281/zenodo.3554331 - [@bidspm]) |
| 4 | +using statistical parametric mapping |
| 5 | +(SPM12 - 7771; Wellcome Center for Neuroimaging, London, UK; |
| 6 | +https://www.fil.ion.ucl.ac.uk/spm; RRID:SCR_007037) |
| 7 | +using MATLAB 9.4.0.813654 (R2018a) |
| 8 | +on a unix computer (Linux version 5.15.0-53-generic (buildd@lcy02-amd64-047) (gcc (Ubuntu 11.2.0-19ubuntu1) 11.2.0, GNU ld (GNU Binutils for Ubuntu) 2.38) #59-Ubuntu SMP Mon Oct 17 18:53:30 UTC 2022 |
| 9 | +) |
| 10 | +. |
| 11 | + |
| 12 | + |
| 13 | +The preprocessing of the functional images was performed in the following order: |
| 14 | +- removing of dummy scans |
| 15 | +- slice timing correction |
| 16 | +- realignment and unwarping |
| 17 | +- segmentation and skullstripping |
| 18 | +- normalization MNI space |
| 19 | +- smoothing |
| 20 | + |
| 21 | +{{nb}} dummy scans were removed to allow for signal stabilization. |
| 22 | + |
| 23 | +Slice timing correction was performed |
| 24 | +taking the ^th slice as a reference |
| 25 | +(interpolation: sinc interpolation). |
| 26 | + |
| 27 | +Functional scans from each participant were realigned and unwarped using the mean image as a reference |
| 28 | +(SPM single pass; number of degrees of freedom: 6 ; |
| 29 | +cost function: least square) (Friston et al, 1995). |
| 30 | + |
| 31 | +The anatomical image was bias field corrected. |
| 32 | +The bias field corrected image was segmented and normalized to |
| 33 | +MNI space |
| 34 | +(target space: IXI549Space; |
| 35 | +target resolution: 1 mm; |
| 36 | +interpolation: 4th degree b-spline) |
| 37 | +using a unified segmentation. |
| 38 | + |
| 39 | +The tissue propability maps generated by the segmentation |
| 40 | +were used to skullstripp the bias corrected image removing any voxel with |
| 41 | +p(gray matter) + p(white matter) + p(CSF) > 0.75. |
| 42 | + |
| 43 | +The mean functional image obtained from realignement was co-registered to the |
| 44 | +bias corrected anatomical image |
| 45 | +(number of degrees of freedom: 6 ; |
| 46 | +cost function: normalized mutual information) |
| 47 | +(Friston et al, 1995). |
| 48 | +The transformation matrix from this coregistration was applied to all the functional images. |
| 49 | + |
| 50 | +The deformation field obtained from the segmentation was applied to all the functional images |
| 51 | +(target space: IXI549Space; |
| 52 | +target resolution: equal to that used at acquisition; |
| 53 | +interpolation: 4th degree b-spline). |
| 54 | + |
| 55 | +Preprocessed functional images were spatially smoothed using a 3D |
| 56 | +gaussian kernel (FWHM = 6 mm). |
| 57 | + |
| 58 | +## References |
| 59 | + |
| 60 | +This method section was automatically generated using bidspm |
| 61 | +(v2.3.0; https://github.com/cpp-lln-lab/bidspm; DOI: https://doi.org/10.5281/zenodo.3554331) |
| 62 | +and octache (https://github.com/Remi-Gau/Octache). |
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