The best way to assess the quality of the correction is an F-test over the respective physiological noise model regressors in the design matrix. Luckily, if you use SPM, the toolbox can create these contrasts and corresponding output plots with overlays of your brain automatically via calling the following function in the Matlab command window:
Of course, you will have to adapt all paths to your `SPM.mat`, `physio.mat` and `anatomy.nii` files. There are more parameters to set (e.g. F-contrast thresholds), type `help tapas_physio_report_contrasts` for a list of options.
There should be whole-brain multiple-comparison corrected "activation" in physiological noise sites (similar to Fig. 8C or 9 in our [paper](https://doi.org/10.1016/j.jneumeth.2016.10.019).
If your F-contrast results differ or are absent, have a look at the *Diagnostic raw physiological time series*-plot and check whether it resembles Fig. 3 in the paper or whether there are any suspicious spikes in the heart cycle length.
Other than that, scan timing synchronisation is a major source of error, so always check the *Cutout actual scans* plot, whether the curves and scan events, TR etc. make sense.
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