[FieldTrip] fieldtrip Digest, Vol 181, Issue 3

Wed Dec 17 20:10:24 CET 2025

I don't think the answer to the source units is totally correct.

The "sLORETA" is a function of the amplitude of the MNE divided by the S.D. of the local MNE.  So its like a t-score.  The lamba for the inversion is derived in the same was as the MNE, like from the fcn(covariance) of  baseline trials or prestim trials.  dSPM is similar to sLORETA.

The eLORETA is not an A.U..  The eLORETA uses an iterative procedure to find a lambda, then does an MNE type inversion.
 The resulting computation has the same status as the original MNE, i.e..amperes er square mm, microamps per square mm, nanoamps per ...

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-----Original Message-----
From: fieldtrip <fieldtrip-bounces at science.ru.nl> On Behalf Of fieldtrip-request at science.ru.nl
Sent: Wednesday, December 17, 2025 6:00 AM
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Subject: fieldtrip Digest, Vol 181, Issue 3

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Today's Topics:

   1. About source reconstruction outputs (Fabio Strappazzon)
   2. Re: About source reconstruction outputs (ivano triggiani)
   3. Open PhD Position(s) in Perception/EEG – Joint Opportunity
      (David Pascucci)

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Message: 1
Date: Tue, 16 Dec 2025 17:24:52 +0100
From: Fabio Strappazzon <fab.strappaz at gmail.com>
To: fieldtrip at science.ru.nl
Subject: [FieldTrip] About source reconstruction outputs
Message-ID:
        <CAGSg2Yq+WXC4eZiCK1hYW9=53J4oCVdervKtEELvBLLvEkvSLg at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Dear all,

I'm currently using wMNE as inverse operator.
I would like to know two things:

1) What are the units of measure of source reconstructed activity? I see that many papers report them as arbitrary units (a.u.) but I would like to know more why is that the case.

2) Would it be possible to still apply the FieldTrip functions for calculating PSDs (ft_freqanalysis) on outputs from source recontructed data with distributed apporaches (like MNE) or there are some specific functions for those kind of data? If so, on which outputs are calculated: on the source.avg.mom or the source.avg.pow?

Many thanks,

--
*Strappazzon Fabio, *
*PhD Student at ITAB (Institute for Advanced Biomedical Technologies) -
Chieti*
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Message: 2
Date: Tue, 16 Dec 2025 16:44:01 -0500
From: ivano triggiani <ivanotriggiani at gmail.com>
To: FieldTrip discussion list <fieldtrip at science.ru.nl>,
        fab.strappaz at gmail.com
Subject: Re: [FieldTrip] About source reconstruction outputs
Message-ID:
        <CAAb4LYg-NpHa6XFB5EKPzTgKa-XqZiRBNjW3YHJaEAtvc==nhg at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

Caro Fabio,

My humble opinion:

1. Since source reconstruction is a well-known ill-posed problem, every method relies on different constraints. For instance, MNE minimizes the overall L2 norm, which often results in smooth solutions, easily distorted if noise is significant.

To stabilize the solution, regularization methods use, for example, estimation of the noise covariance and a regularization parameter. This scaling process changes the output, which is no longer strictly measured in physical units (like current density) but is reported in a.u. or normalized quantity. sLORETA and eLORETA operate under a similar concept of weighted or standardized normalization (I am simplifying!).

2.  I think so, but you must calculate the PSD on the estimated source time series. For distributed solutions the data is contained in the source.avg.mom field, not source.avg.pow, if I remember correctly.
You need to restructure the source.avg.mom field so that FieldTrip treats each source location as a separate "channel" before running ft_freqanalysis.
Something like:

cfg = [];
cfg.method = 'mtmfft'; % or whatever
cfg.output = 'pow';
cfg.foi = 0.5:0.5:40; % freqs
freq_source = ft_freqanalysis(cfg, source_data);

The resulting PSD may look "weird" compared to sensor-level data because the spatial filter (source method) affects the spectral profile of the noise and signal.
Ciao,

Ivano

---

*A. Ivano Triggiani, Ph.D.*

________________________________________________

On Tue, Dec 16, 2025 at 11:55 AM Fabio Strappazzon via fieldtrip < fieldtrip at science.ru.nl> wrote:

> Dear all,
>
> I'm currently using wMNE as inverse operator.
> I would like to know two things:
>
> 1) What are the units of measure of source reconstructed activity? I
> see that many papers report them as arbitrary units (a.u.) but I would
> like to know more why is that the case.
>
> 2) Would it be possible to still apply the FieldTrip functions for
> calculating PSDs (ft_freqanalysis) on outputs from source recontructed
> data with distributed apporaches (like MNE) or there are some specific
> functions for those kind of data? If so, on which outputs are
> calculated: on the source.avg.mom or the source.avg.pow?
>
> Many thanks,
>
> --
> *Strappazzon Fabio, *
> *PhD Student at ITAB (Institute for Advanced Biomedical Technologies)
> -
> Chieti*
> _______________________________________________
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Message: 3
Date: Wed, 17 Dec 2025 09:14:32 +0100
From: David Pascucci <psc.dav at gmail.com>
To: visionlist at visionscience.com, cvnet at mail.ewind.com,
        comp-neuro at lists.cnsorg.org, SPM at jiscmail.ac.uk,
        announcements at lists.cognitivesciencesociety.org,
        fieldtrip at science.ru.nl
Subject: [FieldTrip] Open PhD Position(s) in Perception/EEG – Joint
        Opportunity
Message-ID:
        <CAN16468exgnDpRgcvYcfkzFiJdWEKP57kpNjWuQOAUNrc+3-Qg at mail.gmail.com>
Content-Type: text/plain; charset="utf-8"

*Open PhD Position(s) in Perception/EEG – Joint Opportunity*

*Locations:* Lausanne (University of Lausanne / CHUV) and Paris (ENS/CNRS)

*Start Date:* Early 2026 (with some flexibility)

The *Psychophysics and Neural Dynamics Lab* <https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.chuv.ch%2Ffr%2Frad%2Frad-home%2Frecherche%2Fgroupes-de-recherche%2Fpsychophysics-and-neural-dynamics-lab&data=05%7C02%7Cfieldtrip%40science.ru.nl%7C0d1385c42f2a4df3cd4908de3d9ff323%7C084578d9400d4a5aa7c7e76ca47af400%7C1%7C0%7C639015954370450426%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=DFNKU32c0z0lPae8GJGFJxWNx8TFdmHm3KMAOl1t%2BsA%3D&reserved=0>
(David
Pascucci, University of Lausanne and Lausanne University Hospital, CHUV) and the *Laboratoire des Systèmes Perceptifs* <https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flsp.dec.ens.fr%2Fen%2Fmember%2F647%2Fpascal-mamassian&data=05%7C02%7Cfieldtrip%40science.ru.nl%7C0d1385c42f2a4df3cd4908de3d9ff323%7C084578d9400d4a5aa7c7e76ca47af400%7C1%7C0%7C639015954370475200%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=JnhXf1WEXgKJWmS8awlWWuyTZy0zPmskm2Wy1oM5t%2BY%3D&reserved=0> (Pascal Mamassian,
ENS/CNRS) invite applications for a fully funded PhD position (3 years + 1) supported by the *ANR-SNSF Weave project*.
Project title

*Perceptual FLUCTUATions*
Project summary

Our 4-year project addresses a central question:

*Why do individuals differ in how their perceptual judgments are shaped by temporal context?*

We will address this through an integrated behavioural, computational, and neurophysiological approach, focusing on the interaction between endogenous perceptual traits and external factors.

The work involves *visual psychophysics, EEG, and computational modeling*.
The successful candidate will be primarily based in *Lausanne*, with research visits to *ENS/CNRS*, allowing engagement with two complementary research environments.
Candidate profile

Applicants should hold a *Master’s degree* in Neuroscience, Psychology, Biology, Engineering, Computer Science, Mathematics, or a related field.
Experience in *visual psychophysics and/or EEG* is strongly valued.
Preferred skills

·  Psychophysics software (e.g., PsychoPy, Psychtoolbox)

·  Programming (e.g., Python, MATLAB, C/C++)

·  EEG and/or signal processing, computational modeling

·  Statistical analysis (e.g., in R)

·  Dedication to data collection in task batteries

We seek *dedicated, enthusiastic candidates* with strong motivation to contribute to interdisciplinary research.

We welcome applications from candidates of *all backgrounds and genders*.
Application material

Applications should include:

1.    Most recent *CV*

2.    Documents confirming a *Master’s degree* or equivalent

3.    Records of *academic achievement* at undergraduate and graduate levels

4.    *Statement of intent*, describing why you are a good fit for the
position

5.    *Two letters of recommendation* (or email addresses) from qualified
academics familiar with your work

We value application materials that reflect your own words and authentic, human-written motivation.

Applications are considered *on a rolling basis* until the position is filled.

*Early applications are encouraged to accommodate the planned start in early 2026.*

*Please note:*

We are also planning to recruit *postdoctoral researchers* in the near future, so stay tuned!

Contact

To submit your application, please send all materials to:

pndlab24 at gmail.com

For informal inquiries, feel free to contact:

david.pascucci at chuv.ch

pascal.mamassian at ens.fr

We look forward to hearing from you!
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