HI Melanie
Yes that is exactly how to get the time-courses out.
So I am hoping you want to know the answer for MEG right ? ... if not I hope an EEG colleague will chip in- if they don't please remind me and I will look it up.
For MEG. The link between J and current density in the cortex is more subtle. J is actually equivalent dipole moment. (lets call it Q from now on).
Where Q=IL. So if you imagine say a cylinder of cortex generating a dipole moment, L would be the length of the cylinder and I the total current flow.
and then total current flow I=cA where c is longitudinal current density and A is the cross-sectional area of the cylinder.
Hope this helps.
Best
Gareth
-----Original Message-----
From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] On Behalf Of Melanie Boly
Sent: 13 October 2015 17:30
To: [log in to unmask]
Subject: [SPM] SPM source reconstruction output - full set of time courses
Dear SPM team,
We are working on trying to use SPM source reconstruction outputs for source space traveling wave analyses (like in Murphy et al. PNAS 2009
- http://www.ncbi.nlm.nih.gov/pubmed/19164756).
Basically this analysis involves reconstructing source current density at each time point for all mesh vertices and then track spatial traveling of currents using streaming algorithms.
I was wondering if it is correct that whole-brain source reconstructed time course results can be obtained using:
full_output_timecourses = J*T'
where J is SPM 12's D.other.inv{1}.inverse.J{1,:} (the source amplitude conditional expectation) - in my example output
(5124 vertices x 16 modes)
and T is SPM 12's D.other.inv{1}.inverse.T (the temporal projector) - in my example output (16 modes x 4001 time points)
It seems that in SPM12 spm_eeg_invert_display would use such a formula (in line 143) for reconstructing time course of activity for a selected single source when called from the GUI.
Would the current source density be equivalent to the absolute value of the obtained time courses?
Thanks so much in advance for your help, Melanie Boly
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