[FieldTrip] dipole fitting for studing resting states

[Matti Stenroos]

Hello Irene,

Dipole fitting is used, when one has prior knowledge that the data is 
supposed to arise from one (single-dipole) or a couple of (multi-dipole) 
focal source regions. In event-related analysis, one typically studies a 
phenomenon that is (assumed to be) time-locked to the stimulus and 
repeated (almost) identically stimulus-by-stimulus. Then, giving many 
stimuli and averaging the data, one can suppress other brain activity 
and bring up the studied phenomenon. If the phenomenon is supposed to 
arise from focal region(s), for example in the case of somatosensory 
evoked potentials, dipole fitting can perform excellently.

If one has no such prior information / study setting, dipole fitting is 
not necessarily useful. In classical dipole fitting, one explains the 
measurement using the dipoles. A couple of dipoles often explain the 
data very well, but that does not mean that the result would make any 
sense. So, in resting-state data, one rather selects a method that a) 
explains the data using the whole brain space, or b) uses a spatial 
filtering approach that scans the source space without aiming to explain 
the measurement. Case a) would be minimum norm estimation and case b) 
for example beamforming.

Cheers,
  Matti





On 29/05/2019 17.18, Irene Varela Leniz wrote:
> Dear Fieldtripers,
> 
> I am following the tutorial "Dipole fitting of combined MEG/EEG data". 
> Here, there is a sentence /"information about how to fit dipole models 
> to the event-related fields (MEG) and potentials (EEG) of a single 
> subject". /Does the author want to express with this that the approach 
> dipole fitting is  used with Event Related Potentials?
> 
> I have been looking in literature and have only found studies based on 
> beamforming to study resting states. Does anyone know if the approach 
> dipole fitting can also be used in these cases? Or is it more convenient 
> to rely on beamforming approaches?
> 
> Thank you for your attention.
> 
> Best regards,
> 
> Irene
> 
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