[Eeglablist] Source localization and hippocanpus

Thu Jan 15 09:04:56 PST 2026

I perhaps have a different opinion on this than some of those who have responded, but in my own reading of the literature, hippocampus has always seemed a more plausible solution for source generator of scalp recorded event related potentials than other subcortical structures.

For example, the basal ganglia do not have the required cellular architecture, that is a laminar organization with arrayed pyramidal neurons and dendrites which are aligned spatially to produce synchronous postsynaptic potentials.

Prior results implicating the basal ganglia in the generation of, for example, the reward positivity are more easily explained by a superposition of two sources in the brain, which my current research suggests being medial frontal cortex and posterior cingulate cortex. The same argument was made in a rebuttal to that paper, in which a simulation showed that the same pattern could be easily explained by a two-generator motif.

On the other hand, the hippocampus has the necessary physiology of spatially aligned pyramidal cells which can form synchronous potentials projecting to the scalp surface. This is according to simulation and empirical recordings, for example, depth recordings from hippocampus simultaneous with ecog grid recordings. In this regard, hippocampus is physiologically somewhat unique, and in fact, might be better classified as cortical tissue rather than subcortical based on some of these features.

Best,
Eric Rawls

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________________________________
From: eeglablist <eeglablist-bounces at sccn.ucsd.edu> on behalf of Philip Zeman via eeglablist <eeglablist at sccn.ucsd.edu>
Sent: Thursday, January 15, 2026 10:45:51 AM
To: Евгений Машеров <emasherov at yandex.ru>
Cc: eeglablist at sccn.ucsd.edu <eeglablist at sccn.ucsd.edu>
Subject: Re: [Eeglablist] Source localization and hippocanpus

[This email originated from outside of UNCW]

Hi Eugen,

in my own past work I found sources (expected) in hippocampal/temporal
regions. The ICA and volume localization I used implicated parts parts of
the temporal lobe together with the hippocampus.

I'm glad you're looking into this.

Philip

On Thu, Jan 15, 2026 at 5:24 AM Евгений Машеров via eeglablist <
eeglablist at sccn.ucsd.edu> wrote:

> Using source localization methods, we were able to find foci located in
> the hippocampus. These were confirmed during surgery. This is difficult to
> explain from the standpoint of pure dipole theory, and is one of the
> motivations for me to develop a method that takes into account non-dipole
> sources. The field they generate may weaken with increasing distance less
> dramatically than that of a dipole, and the task of reconstructing the
> signal from deep sources may not be so hopeless.
>
> Eugen Masherov
>
> > We made a good case that the Feedback Negativity (FN) originates from
> > the striatum (Foti, Weinber, Dien, & Hajcak, 2011, 2011). It's not a
> > claim to be made lightly. The cortex is a strong candidate as far-field
> > generators because it is rich on pyramidal neurons, which have
> > asymmetrical dendrites and tend to be oriented in the same direction,
> > but that does not mean it is the only possible source. To make a case
> > for a subcortical generator, you have to be able to demonstrate
> > convergent validity with data from methods like intracranial EEG
> > recordings. See our papers for arguments and references.
> >
> > The hippocampus, on the other hand, is the classic example of a
> > structure that is likely to be a closed field generator because it is in
> > the form of a tube, wherein the field from a given neuron is likely to
> > be canceled out by the field from a neuron pointing the opposite
> > direction on the other side of the tube, resulting in a net zero voltage
> > field when measured from outside the tube. No amount of electrodes or
> > computational sophistication is going to help with that. Of course,
> > it's all complicated because the entire tube isn't necessarily equally
> > active. Also, the adjoining parahippocampal cortex isn't a tube. There
> > seems to be a lot of discussion going on right now about what can be
> > measured. But yeah, making a plausible claim for a hippocampal
> > generator would require very strong evidence. As John says, it's easy
> > to put a equivalent dipole in the hippocampal region and get non-zero
> > results, so not strong evidence by itself. But I'd also be wary of
> > making sweeping generalizations.
> >
> > Joe
> >
> > Foti, D., Weinberg, A., Dien, J., & Hajcak, G. (2011). Event-related
> > potential activity in the basal ganglia differentiates rewards from
> > nonrewards: Temporospatial principal components analysis and source
> > localization of the feedback negativity. /Hum Brain Mapp/, /32/(12),
> > 2207–2216.
> https://urldefense.com/v3/__https://nam12.safelinks.protection.outlook.com/?url=https*3A*2F*2Furldefense.com*2Fv3*2F__https*3A*2F*2Fdoi.org*2F10.1002*2Fhbm.21182__*3B!!Mih3wA!F6lfB756tGdH_QFKwL5mIWetNG672s_aafnqgyt9T8wO7nrcuWuqfT_GvDz4sGND_j85H6f_kjzDtWSplqI*24&data=05*7C02*7Crawlse*40uncw.edu*7C238d864b84a4401caa6b08de54571c18*7C2213678197534c75af2868a078871ebf*7C0*7C0*7C639040930287599901*7CUnknown*7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ*3D*3D*7C0*7C*7C*7C&sdata=XQzDyx7Fz72*2BN3NhWktVpA4qfO10WaaQSLuxofAMOiU*3D&reserved=0__;JSUlJSUlJSUlJSUlJSUlJSUlJSUlJSUlJSUlJSUl!!Mih3wA!C2eTgr5iCaCFZ_g6V1tvubkxCI-7YPqfxTxDcTu15VWELjkJhrNv4IFKudn0-gHqVeh52miAnJhoPix8fi4_rg$ <https://urldefense.com/v3/__https://doi.org/10.1002/hbm.21182__;!!Mih3wA!F6lfB756tGdH_QFKwL5mIWetNG672s_aafnqgyt9T8wO7nrcuWuqfT_GvDz4sGND_j85H6f_kjzDtWSplqI$>
> >
> > Foti, D., Weinberg, A., Dien, J., & Hajcak, G. (2011). Event-related
> > potential activity in the basal ganglia differentiates rewards from
> > nonrewards: Response to commentary. /Hum Brain Mapp/, /32/(12),
> > 2267–2269.
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> >
> > On 1/14/26 18:52, Richards, John via eeglablist wrote:
> >
> >> The hippocampus, caudate, putamen, amygdala, sometimes are classified
> with "cortex" as gray matter and people might try to do source analysis.
> However, only the cortex has the perpendicular pyramidal structure that
> conducts current to the scalp, and the "subcortical" brain areas do not
> have the correct structure to generate current on the scalp. If you put
> source locations in these areas and do source analysis you will get
> "something", likely due to activity in other brain areas, noise, or other
> non-neuron activity.
> >>
> >> I think that a couple of the "internal" cortex ROIs, like the insula,
> have the cortex structure to generate current. But its possible that it
> cannot be measured because the area is relatively far from the scalp and
> any current would be small.
> >>
> >> John
> >>
> >> ***********************************************
> >> John E. Richards
> >> Carolina Distinguished Professor
> >> Department of Psychology
> >> University of South Carolina
> >> Columbia, SC 29208
> >> Dept Phone: 803 777 2079
> >> Fax: 803 777 9558
> >> Email:richards-john at sc.edu
> >>
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> >> ***********************************************
> >>
> >> -----Original Message-----
> >> From: eeglablist<eeglablist-bounces at sccn.ucsd.edu> On Behalf Of Cedric
> Cannard via eeglablist
> >> Sent: Wednesday, January 14, 2026 3:43 PM
> >> To: EEGLAB List<eeglablist at sccn.ucsd.edu>
> >> Subject: [Eeglablist] Source localization and hippocanpus
> >>
> >> Hi everyone,
> >>
> >> My understanding is that it is impossible to reliably pick up activity
> from the hippocampus when doing any form of source
> localization/reconstruction from 64 channels EEG data (or more?). Is that
> still correct or are there solutions I am not aware of?
> >>
> >> Thanks,
> >>
> >> Cedric
> >>
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> >
> --------------------------------------------------------------------------------
> >
> > Joseph Dien, PhD
> > Senior Research Scientist
> > Department of Human Development and Quantitative Methodology
> > University of Maryland, College Park
> > E-mail:jdien at umd.edu
> >
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