[Eeglablist] Critical pitfall of spectral power analysis?

[장진원]

Dear all,

Thank you for sharing all the interesting ideas in this topic. I just
wonder whether utilizing the derivative of the EEG time series to minimize
1/f scaling (Cox et al., 2017) is more or less effective than other methods
like FOOOF or GLM proposed by Cedric.

Best Regards,
Jinwon Chang

2025년 9월 18일 (목) 오후 11:29, Makoto Miyakoshi via eeglablist <
eeglablist at sccn.ucsd.edu>님이 작성:

> Hello Mate and all,
>
> I became curious about the 1/f^n issue, so I spent a whole day today
> investigating this problem.
> Following Cedric's obsession, I uploaded simulation code and results to
> Github, YouTube, and SCCN Wiki page.
>
> https://urldefense.com/v3/__https://github.com/MakotoMiyakoshi/cableTheoryDemo/tree/main__;!!Mih3wA!CORpSZkbn8mntguT3SylRvIRIqrj-8phD2Bm9zBE0rNFZZa8DMJcfa0mXv2pG2xDJfbgRregAtjdLfj53TBo4g-7dEc$
>
> https://sccn.ucsd.edu/wiki/Makoto%27s_preprocessing_pipeline#Where_does_power_distribution_come_from.3F_.28For_510.2C000_page_views.2C_Added_on_09.2F17.2F2025.29 
>
> https://urldefense.com/v3/__https://www.youtube.com/watch?v=SitmGp8LYtY__;!!Mih3wA!CORpSZkbn8mntguT3SylRvIRIqrj-8phD2Bm9zBE0rNFZZa8DMJcfa0mXv2pG2xDJfbgRregAtjdLfj53TBosE7VLyc$
>
> https://urldefense.com/v3/__https://www.youtube.com/watch?v=iaRQsaU1_2s__;!!Mih3wA!CORpSZkbn8mntguT3SylRvIRIqrj-8phD2Bm9zBE0rNFZZa8DMJcfa0mXv2pG2xDJfbgRregAtjdLfj53TBoDhtKxC8$
>
> I think the mechanism you are referring to, Makoto, is what's usually just
> described as "dendritic filtering", is it not? I'm aware of this process
> plus the low-pass filtering that happens as a consequence of spatial
> summation.
>
>
> Yes, a dendritic filtering. But to be honest I was not aware of the fact
> that there were actually two scenarios, one is passive (like EFB) and the
> other is active (like Gao et al.)
> I once asked Paul whether the subthreshold passive cable theory was
> sufficient to explain the generative model of EEG signals. He said the
> subthreshold model was 'good enough'. As I read Reimann et al. (2013) this
> time, I found that the difference between passive vs. active cable is
> present but probably not very critical after all. As we can easily imagine,
> the active model with action potentials adds more power at higher
> frequencies (in FOOOF terminology, 'flatter aperiodic') If I were an
> American, I would say duh--action potentials are spikes. But Reimann and
> colleagues also investigated the impact on laminer CSD patterns, which was
> good to confirm.
>
> As my simulation confirms, we can make testable hypotheses on modulation of
> 1/f-ness.
> For example, selective engagement of pyramidal neurons whose soma are at L5
> should show more low-pass filter effect simply because their dendrites are
> longer than those that reside at L3.
> Also, any preferential engagement of neural populations that are known to
> use non-myelinated axons should produce more low-pass filter effects etc
> etc..
>
> I want to see a quantitative comparison between the dendritic length model
> within the framework of the passive cable theory and AMPA/GABA_A model
> within the framework of Gao's action potential-based model. Is the latter
> so prominently larger than the former so that we can safely forget it? It's
> an empirical question.
>
> Makoto
>
>
> On Sun, Aug 31, 2025 at 6:30 PM Gyurkovics, Mate <mategy at illinois.edu>
> wrote:
>
> > Thanks again for all the interesting points. I'm certianly learning a lot
> > on the physics side - and also about the PSD in different animals, I was
> > genuinely unaware of all this, but sounds super interesting.
> >
> > I think the mechanism you are referring to, Makoto, is what's usually
> just
> > described as "dendritic filtering", is it not? I'm aware of this process
> > plus the low-pass filtering that happens as a consequence of spatial
> > summation. These are the two main ones I was thinking of, so you are
> right,
> > it was very imprecise on my part to talk about the low-pass filtering
> > properties of the tissue.
> >
> > As demonstrated in a classical study by Lopes da Silva and van
> > Leeuwen (1977), alpha oscillation is generated within the cortex which is
> > only 4-5 mm thick.
> >
> > Just out of curiosity, what point was this sentence supporting?
> >
> > I'm very happy to learn the conceptual distinction between trivial and
> > non-trivial contributions to the changes of 1/f power distribution. Thank
> > you Mate. Your works are impressive.
> >
> > Very nice of you to say this, Makoto - I would, however, also like to
> > stress that this particular distinction just reflects how I personally
> > think about this problem (i.e., the contribution of the ERP to the
> > spectrum), I'm sure reasonable people could disagree. (Although this is
> > basically the logic we published in the Journal of Neuroscience paper
> > linked above.)
> >
> > @Eugen - you raise many interesting points. (I certainly agree that in
> > scalp recordings at leat, oscillatory activity is sparse, and most
> robustly
> > occurs when the brain is not engaged with a task, in the form of alpha
> > activity, but that is about as bold as I can be here.)
> >
> > is sinusoidal (with sharp peaks in the spectrum) activity and broadband
> > (not necessarily 1/f) activity generated by different mechanisms?
> >
> > I think, to put it very simply, this is one of the fundamental questions
> > underlying this discussion here. If they are separate AND fairly
> > independent, that is when the conclusions of our paper hold. If they are
> > separate but interact, our conclusions will sometimes hold, other times
> > maybe not. If they reflect the same underlying mechanism, our conclusions
> > would likely rarely be a concern. I personally think that they likely
> > reflect mechanisms that are separate at least to some extent - plus
> > 1/f-like broadban activity likely reflects several, not just one,
> > generative mechanisms as highlighted by Makoto and others here too.
> >
> > Moreover, the function 1/f may simply be the result of the Fourier
> > transform of a single excitatory or inhibitory postsynaptic potential.
> >
> > As far as I recall, this point is covered in Gao et al. (2017), the paper
> > that first linked 1/f-like features to excitation/inhibition balance.
> >
> > Thanks,
> > Mate
> >
> >
> >
> >
> >
> >
> >
> >
> > ------------------------------
> > *Feladó:* Евгений Машеров <emasherov at yandex.ru>
> > *Elküldve:* 2025. augusztus 30., szombat 9:07
> > *Címzett:* Gyurkovics, Mate <mategy at illinois.edu>
> > *Másolatot kap:* EEGLAB List <eeglablist at sccn.ucsd.edu>; Wirsing,
> Karlton
> > <kwirsing at vt.edu>; Cedric Cannard <ccannard at protonmail.com>; 장진원 <
> > jinwon06292 at gmail.com>; Makoto Miyakoshi <mmiyakoshi at ucsd.edu>
> > *Tárgy:* Re: [Eeglablist] Critical pitfall of spectral power analysis?
> >
> > As a (naive and insufficiently substantiated hypothesis) — is sinusoidal
> > (with sharp peaks in the spectrum) activity and broadband (not
> necessarily
> > 1/f) activity generated by different mechanisms? Moreover, sinusoidal
> > activity is a manifestation not of action, but of inaction of the brain.
> > Physiological (alpha rhythm when closing the eyes, possibly also mu
> rhythm
> > in the absence of proprioceptive signals, sleep spindles) or pathological
> > (alpha coma and low-frequency sinusoids in the delta or theta ranges). It
> > can be associated with the regulation of the level of constant potential
> > and, in general, with metabolic processes carried out by the integral
> > regulator generating oscillations (but we see oscillations directly only
> as
> > an idle rhythm). Broadband activity seems to be directly associated with
> > the functioning of individual neurons. Moreover, the function 1/f may
> > simply be the result of the Fourier transform of a single excitatory or
> > inhibitory postsynaptic potential. These mechanisms are interconnected,
> but
> > different. Perhaps the mathematical apparatus for their study should also
> > be different.
> >
> > Your truly
> >
> > Eugen Masherov,
> > Burdenko Neurosurgery Institute
> >
> > > Thanks again everyone, for these very interesting points.
> > >
> > > Just to add to something that was said recently - yes, 1/f (or rather,
> > 1/f^x) features are quite ubiquitous, I think practically any time series
> > with some amount of autocorrelation will have a similar shape:
> >
> https://urldefense.com/v3/__https://www.cell.com/trends/cognitive-sciences/fulltext/S1364-6613(14)00085-0__;!!Mih3wA!E0DB3LnNc6JHuXWc3N5M5iAUeusaX8LTN3dqbu9ZUeyzmDOwf3GVazliJU65YVxC6mC4VLMvHBOlkHKz4AeGoXXj$
> > - its ubiquity is covered nicely in this lovely paper, as far as I
> remember.
> > >
> > > I also get most of Makoto's points about how just the location of the
> > neuronal inputs, either in terms of proximity to the soma or in terms of
> > cortical layers, will affect the strength of the low-pass filtering, and
> > thus the shape of the 1/f scaling. This is super interesting, and this
> and
> > dendritic filtering are certainly discussed in the literature to some
> > extent. I am a bit more sceptical whether such subtle differences could
> > contribute to 1/f changes in scalp recordings, but Makoto suggests they
> > could and I trust his expertise.
> > >
> > > If you perform an ERP task, it would change 1/f power distribution, not
> > surprisingly, because task-triggered cortico-cortical and
> thalamo-cortical
> > inputs are recruited.
> > >
> > > This is a very interesting point. In our 2021 paper linked above, we
> > also make the point that 1/f shape should change in an event-related
> > design, but for a more trivial reason: ERPs are non-oscillatory (in the
> > simple sense that they are transient bursts that do not repeat with a
> clear
> > period), and will thus have a 1/f shape in the frequency domain (indeed,
> > they do, there are some figures in the paper). Thus, 1/f scaling will
> > change after an event trivially because there are well-known
> > non-band-limited changes happening in the EEG (the ERPs). We tried to
> > correct for the contribution of the ERPs and still found post-stimulus
> 1/f
> > changes that we consider non-trivial (a steepening to be specific).
> These,
> > then, could be explained by the mechanism that Makoto suggests (which we
> > did not consider in the paper, as it seemed maybe a bit small-scale to
> > explain scalp-derived effects) and/or by Gao et al.'s
> excitation-inhibition
> > balance idea (this is the framework we used in the paper). It certainly
> > cannot be explained by the general low-pass filtering properties of the
> > tissue or similar more or less fixed variables, as those should not
> change
> > so rapidly.
> > >
> > > I share much of your scepticism about oscillatory mechanisms (in scalp
> > recordings), Makoto, but if we take the most typical generative
> mechanisms
> > assigned to these phenomena (interplay of pyramidal cells and
> > interneurons), they seem like they could potentially interact with these
> > other mechanisms described above, or be fairly independent.
> > >
> > > So we've got this really complex picture, where there could be
> > oscillations going on (maybe in alpha only), there could be
> (independent?)
> > 1/f dynamics happening for multiple reasons, e.g., because of the
> location
> > and/or the nature (E vs. I) of neuronal inputs changing, and there could
> be
> > ERPs happening too, which might partly be phase-locked oscillations, and
> > could also be related to where the neuronal inputs are located, so they
> > "straddle" these different mechanisms quite a bit, probably. Not too sure
> > about the ERPs to be honest.
> > >
> > > Two more minor points:
> > >
> > > I can't put up with the fuzziness of how the term 'oscillation' is used
> > in the field now. Is a try-phasic burst, such as a classical
> event-related
> > N1-P1 waveform, an oscillation?
> > >
> > > I agree completely that it is very unclear what constitutes an
> > oscillation - basically, how many cycles are enough for something to be
> > considered an oscillation, and how do we show that those cycles come from
> > the same generative mechanism, and not just multiple successive events
> > happening. This is less of a question for longer, more stable
> oscillations,
> > e.g., alpha at rest.
> > >
> > > And as for Michael's question: my limited experience with this topic
> > would certainly suggest that 1/f dynamics (for whatever reason) could
> > change very rapidly, and often in a systematic fashion (e.g., predictably
> > after a stimulus). They also do seem to change on much slower time scales
> > as well, e.g., across the lifespan.
> > >
> > > Thanks,
> > > Mate
> > >
> >
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