[FieldTrip] very low sLORETA values

[Schoffelen, J.M. (Jan Mathijs)]

Hi Kirill,

I don’t know where you got the quote from, so I cannot comment on what I would expect as output units, but I suggest that you check the documentation of the ft_sloreta function, and/or read in the code what is actually done to generate the function’s output.

My suspicion is that what is called ’sloreta’ in fieldtrip does not correspond to the ‘classical’ definition of sloreta that you refer to. From the top of my head already a big difference would be that the original sloreta is a distributed sourcemodel, which is typically obtained using a single inversion step,  while the implementation in fieldtrip seems to run a ’scan’ dipole per dipole, and seems to follow the formulation in the Sekihara and Nagarajan book. Whether or not these in the end of the day are equivalent: I don’t know. (And at the moment I find it way too hot to think about this)

Best wishes,
Jan-Mathijs







On 25 Jun 2020, at 17:49, Кирилл Комаров <koman888 at mail.ru<mailto:koman888 at mail.ru>> wrote:

Dear Fieldtrippers,
        I am doing a research of auditory ERP.
        I've performed source reconstruction using sLORETA method.
        'The dSPM and sLORETA values are statistical scores akin to z-scores and F-scores; therefore they are unit-less and can be interpreted at deviation from “standard fluctuations” as defined from noise or baseline variance stats for instance.
        I want to understand why sLORETA applied to data produces so small values for time-courses:
        1e-10, 1e-9?
Meanwhile dSPM yields time-courses in the range 1e+1 - 1e-1.
        Could You explain or post a reference link?
        Best wishes,
        Kirill


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