Signal simulation by dSPM unconstrained source map

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I have computed the BEM head model in MRI volume source space and then computed source using dSPM method. However, when I tried to reconstruct/simulate the signal, there was an error for the simulation.

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I want to know how the following progress can be done using brainstorm, especially the reconstructed signal from dSPM source map:
" For each patient, we constructed a forward model with boundary element method using OpenMEEG. Source space included one or both hemispheres depending on the implanted electrodes’ locations. For each propagating event, we solved the inverse problem using dynamic statistical parametric mapping (dSPM) obtaining spatiotemporal unconstrained dipole maps of time windows with 500 ms duration (from −200 to 300 ms, with 0 corresponding to the first onset spike) using Brainstorm. This duration was selected to capture the entire propagation phenomenon, based on prior findings showing a maximum duration of 250 ms. We considered the data covariance matrix to be all windows centred around each spike's onset with a 200 ms duration, and the noise covariance to be the identity matrix. To reduce the source spurious activity, we considered windows with a correlation above 0.7 between the reconstructed and original signal."

Reference:
Matarrese MAG, Loppini A, Fabbri L, Tamilia E, Perry MS, Madsen JR, Bolton J, Stone SSD, Pearl PL, Filippi S, Papadelis C. Spike propagation mapping reveals effective connectivity and predicts surgical outcome in epilepsy. Brain. 2023 Sep 1;146(9):3898-3912. doi: 10.1093/brain/awad118. PMID: 37018068; PMCID: PMC10473571.

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Sources estimated with dSPM cannot be directly used to reconstruct the MEG/EEG signals, because the dSPM sources are the minimum-norm sources normalized to the noise in each source location. Thus at each source location the sources have been scaled in a different way, which besides removing the physical units, changes the magnitude relationship among sources, so it is not appropriated to use the forward model on these normalized sources.

If you want to reconstruct the MEG/EEG signals, you could use the source estimation using MN imaging and the current density map option.

@Sylvain, any thoughts on this?

@Jixiang, I just realized this is a repost of the question, the previous which as not answered is now delete. Apologies for the answer delay.

3

Thank you very much, I have understood that dSPM source couldn't be used to reconstruct the signal. However, the reference article (Matarrese, 2023) actually used the dSPM method to compute source map. Maybe I shall ask the author how they reconstruct the signal. Thank you again for your answer!