[Eeglablist] Open online discussion: How Do Cable Theory and AMPA/GABA Balance Compare in Their Contributions to 1/f?

[Ching-Ming Lee]

Dear Makoto,

Thank you for the insightful response and for suggesting the term
"System Health Index." It perfectly encapsulates our observation that
the 1/f exponent can serve as a dynamic barometer for the functional
boundaries of neural networks. We initially embarked on this analysis
because of a recurring clinical paradox: we noticed that some patients
showed signs of cognitive decline or 'regression' after excessive rTMS
sessions. However, without objective metrics, these observations
remained anecdotal. Our EEG findings, particularly the 'Network
Collapse' beyond a certain exponent threshold, finally provide a
biophysical basis for these clinical warnings. It turns out that what
the clinicians 'felt' was happening is exactly what the neural network
topology shows.

Regarding your question: No, we have not published this finding yet.
The manuscript is currently a work in progress. We are currently
refining our preprocessing pipeline—specifically comparing GEDAI  with
ASR+ICA—to ensure that the non-linear "Network Collapse" we observed
at higher exponents (e.g., ~1.8) is robust and not an artifact of
signal processing.

I am particularly intrigued by your list of contributors to 1/f-ness.
In our upcoming paper, I hope to argue that while cable theory and
spatial averaging provide a stable biophysical baseline, the dynamic
shifts we see under intensive rTMS are likely driven by acute
modulations in synaptic kinetics and thalamo-cortical state
transitions.

The invertebrate comparison you shared is brilliant. It suggests that
as the exponent increases towards a certain limit, the brain might
lose the specific "complexity" required for high-level information
processing, leading to the topological breakdown we recorded.

I would be happy to share a preprint with the list once our validation
is complete.

Best regards,

Ching-Ming

Makoto Miyakoshi via eeglablist <eeglablist at sccn.ucsd.edu> 於
2026年4月27日週一 上午7:41寫道：
>
> Hi Ching-Ming,
>
> when the exponent reaches a certain threshold (~1.8 in our case), we
> observe a non-linear 'Network Collapse' in global efficiency (via
> WPLI analysis).
>
> This implies that the 1/f exponent might be a 'System Health Index' that
> tracks how close the neural cable is to its functional boundaries.
>
>
> That sounds very interesting. Did you publish the finding?
>
> My understanding is that multiple factors contribute to 1/f^a-ness of EEG
> power. I can at least list
>
>    - Spatial averaging (more spatial averaging for high frequency activity)
>    - Cable theory (aka dendritic filter)
>    - AMPA_A/GABA receptor (Antonio was absolutely right when he wrote "what
>    matters is their decay kinetics" This is why AMPA_A/GABA stuff can be
>    'trivial', as Yevgeny once wrote, if you can predict FFT results from
>    time-domain signals.
>    - Infraslow EEG component due to quasi-stationary current loop between
>    dendrites and soma (I will submit this interpretation soon)
>    - Thalamo-cortical dysrhythmia proposed by Llinas and colleagues in case
>    of pathological conditions
>
> Now it may rather be difficult to imagine how 1/f does NOT occur. Regarding
> this question, I found an interesting study reporting that invertebrate
> shows less 1/f-ness in their nervous system. I quoted their results below
> for your interest. This comparison seems to provide a useful insight.
> https://urldefense.com/v3/__https://github.com/sccn/OneOverF/discussions/16__;!!Mih3wA!Fd4oBZHv8fvFuWhCS5WK-B-Uz55k_1_LIuy1zBgV_pHndN5Ty_oQ46QBv4QgVr8cSdfhND2LtDFmTDsAPfh2-PpNAyw$
>
> Makoto
>
>
> On Wed, Apr 15, 2026 at 8:16 PM Ching-Ming Lee <chingming.lee at gmail.com>
> wrote:
>
> > Thank you all for these profound insights. I find the 'variable RC
> > circuit' perspective particularly compelling.
> > From a biophysical standpoint, if we view the neuron as a dynamic
> > cable, the opening and closing of ion channels (gating) essentially
> > represent the real-time modulation of resistance (R) and capacitance
> > (C). In this framework, the E/I balance is not a competing theory, but
> > rather the functional driver that dictates these parameter shifts.
> > Our longitudinal n-of-1 data suggests that while the anatomical
> > structure sets the 'static' baseline of the cable, interventions like
> > rTMS trigger a dynamic state-shift in these RC properties. The most
> > intriguing finding is that this shift isn't infinite; when the
> > exponent reaches a certain threshold (~1.8 in our case), we observe a
> > non-linear 'Network Collapse' in global efficiency (via WPLI
> > analysis).
> > This implies that the 1/f exponent might be a 'System Health Index'
> > that tracks how close the neural cable is to its functional
> > boundaries. It’s a beautiful intersection where cable theory provides
> > the physical medium, while E/I dynamics provide the regulatory signal.
> > I would be curious to hear your thoughts on whether this 'Network
> > Collapse' could be interpreted as the point where the RC parameters
> > reach a state of functional saturation or over-inhibition.
> >
> >
> > Евгений Машеров via eeglablist <eeglablist at sccn.ucsd.edu> 於
> > 2026年4月15日週三 下午10:42寫道：
> > >
> > > >Hi Ching-Ming, Yevgeny, and Cedric,
> > >
> > >  >Thank you for sharing your experience and results!
> > >
> > >  >*Structural Stability vs. Dynamic Change:* Since the subject's neuronal
> > >  morphology (cable theory properties) cannot change by 60% within 3
> > hours,
> > >  this massive shift provides strong evidence that *E/I balance
> > >  (GABA-mediated inhibition)* is the primary driver of 1/f *dynamics*,
> > >  even if cable theory sets the *baseline*.
> > >
> > >  >Cable theory describes that when a neuron receives synaptic inputs at
> > >  synapses that are located further from the soma, it generates more
> > low-pass
> > >  filtered post-synaptic potential. See a nice illustration from Rall et
> > al.
> > >  (1967)
> > >
> > https://urldefense.com/v3/__https://github.com/sccn/OneOverF/discussions/8__;!!Mih3wA!DHtN8b_WLfq9LU0kcatC6qilNfGVpUWCoDhdGUr5gz4qcT4adsUlFefUMcDmaZVmsSJ6ai6Kq6mOCrDe05dArQOcMds$
> > >
> > >  >Stephanie Jones' human neocortical neurosolver (HNN) has an explicit
> > 2x2x2
> > >  models: cells at layer 2/3 and 5, distal and proximal inputs, and
> > >  excitatory (pyramidal neurons) and inhibitory (basket cells) neurons.
> > Among
> > >  these parameters, 'distal input' is likely to be associated with 'more
> > >  low-pass filtered post-synaptic membrane potentials'.
> > >
> > >  >Ching-Ming, thus the question is 'Can TMS (or any other intervention)
> > >  change the balance between distal and proximal inputs?' This is much
> > >  trickier than thinking whether or not neural morphology can change by
> > 60%
> > >  in 3 hours.
> > >
> > > > We can think of synaptic inputs to apical dendrite in superficial
> > layers as
> > >  a typical case of 'distal input'. If TMS (or any other intervention
> > such as
> > >  hyperventilation) can increase relative amount of 'distal input', that
> > >  would shift 1/f to 'steeper' = 'as if GABA_A-R is dominant at the
> > >  measurement site'.
> > >
> > > > What can increase inputs to apical dendrite? I published a paper last
> > year
> > >  that extralemniscal thalamic (EXLEM) projection goes to the superficial
> > >  layers (about 25%; See 'type 2' in this illustration
> > >
> > https://urldefense.com/v3/__https://github.com/sccn/OneOverF/discussions/17__;!!Mih3wA!DHtN8b_WLfq9LU0kcatC6qilNfGVpUWCoDhdGUr5gz4qcT4adsUlFefUMcDmaZVmsSJ6ai6Kq6mOCrDe05dAARwz5uE$
> > ). EXLEM is the same as
> > >  'non-specific thalamus' mentioned by Grey Walter, Robert Galambos etc..
> > >  Recently, Giandomenico Iannetti has been leading the revival of EXLEM.
> > >
> > >
> > > It's possible that the presence of an effect from transcranial magnetic
> > stimulation doesn't refute the cable theory's explanation of the dependence
> > (although it is extremely interesting information). This is because the RC
> > circuits formed by dendrites, which transform the pulse shape, differ in
> > their properties from those used in radio engineering. Changing resistance
> > or capacitance by applying voltage to a conventional radio engineering
> > resistor or capacitor is impossible (at least until the capacitor breaks
> > down or the resistor burns out) – however, varistors and varicapacitors are
> > also used in radio engineering. Ion solutions, under the influence of the
> > current flowing as a result of magnetic induction, change their
> > concentration, which can change resistance. Channels in membranes can open
> > or close, and the electrical double layer on the membranes can change
> > (possibly related to the "non-specific benefit" of TMS). All of this can
> > affect conductivity and capacitance, thereby generating a pulse shape
> > different from that formed before transcranial magnetic stimulation.
> > >
> > >
> > > > Yevgeny, your reviewer will be angry and tell you you should never
> > call a
> > >  study with n=167 preliminary. Thank you for sharing your results! It is
> > >  good to know that 1/f is not sensitive to hyperventilation.
> > >
> > >
> > > The number is quite large, but to view this as anything more than a
> > preliminary experiment, all these observations must be considered and some
> > discarded. Therefore, these are nothing more than experiments during the
> > debugging of a program designed to analyze a more carefully selected
> > sample. However, since some new information has been obtained, I offer it
> > to your attention, but only as "food for thought," not as conclusive
> > evidence.
> > > I plan to obtain results suitable for full publication, not just as a
> > "personal communication," but to do this, I need to involve clinicians who
> > can assess the suitability of each record for such analysis. I have neither
> > the authority nor the expertise to analyze case histories. This requires
> > time and effort to organize. First and foremost, I need to convince them of
> > the usefulness of this work for them—"it's not so difficult to teach a bear
> > to ride a bicycle than to convince a bear that it needs one." So, what I've
> > submitted for your consideration, I'm not ready to send to a fully
> > peer-reviewed journal until I've thoroughly checked it. If I say something
> > stupid at work, it's my personal shame; if I publish something stupid in a
> > fully-fledged journal, I'll disgrace my colleagues.
> > > And another picture, the distribution of the "alpha" by scalp (median
> > for 167 patients)
> > >
> > > Eugen Masherov
> > >
> > >
> > https://urldefense.com/v3/__https://ibb.co/cSVsWQBB__;!!Mih3wA!HSuCVd5XYQJMfnY5YTX3pu_k-u1q0EHR_OsYCO9ORIt1DjDy9jpQh-uwUymnqmkz2tLYcVW7RtRBynA8CsD1H5I11io$
> > > _______________________________________________
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> >
> >
> >
> > --
> > 李景明
> >
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-- 
李景明