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

[Makoto Miyakoshi]

Hi Yevgeny,

Thank you for sharing that interesting report. I like to read these studies
from the 60's. They are much more understandable to me.

After reading it, I agreed with the view that impedance of the brain as a
volume conductor is rather stable across states. Mostly the fluctuation is
within the range of <10%. This impression confirms a conventional view: EFB
mentions that impedance of the brain is basically stable and linear in the
macroscale, and mostly so in the mesoscale as well, regardless of whether
the neurons are in the resting (subthreshold) or active.

1/f-ness may be more sensitive to state changes than impedance themselves.
Also, frequency dependency of the suggested impedance changes is of
interest to research of 1/f-ness, although I'm pretty sure that within the
EEG frequency range it is rather flat (see
https://urldefense.com/v3/__https://github.com/sccn/OneOverF/discussions/9__;!!Mih3wA!HsORSOi7EJ0QvzN9OxEbKtzee5Ok5k3dIJzClacIz1X_RFMPQrcydxYez3ZOTeSpl2miExXEvh4qTEjg8NIMG4pvbPk$ )

Makoto

On Mon, Apr 20, 2026 at 12:59 AM Евгений Машеров <emasherov at yandex.ru>
wrote:

> Egorov and Kuznetsova's monograph "The Brain as a Volumetric Conductor"
> (published in Russian in 1976, but I think interest in this topic has waned
> somewhat in recent years) presents data on active and reactive resistance.
> Specifically, they note impedance changes with various stimuli, which
> amount to a few percent or more. Here's a machine translation of a fragment
> from pp. 12-17.
>
> "Changes in Brain Tissue Resistance Occurring as a Result of Various
> Functional Shifts
> The electrical resistance values ​​presented in the previous section were
> obtained on nervous tissue under conditions of relative rest. However, the
> resistance of nervous tissue does not remain constant over time. Nervous
> tissue is highly sensitive to various stimuli, and one component of its
> response is a change in electrical resistance.
> Below, we will examine some characteristic cases of changes in brain
> tissue conductivity. In most cases, these are diffuse reactions, and
> therefore lie somewhat outside the scope of this monograph, which is
> devoted to the examination of local inhomogeneities and local shifts in the
> electrical resistance of brain tissue. Nevertheless, we will briefly
> describe the characteristics of these diffuse changes to clarify the
> possible pathways and mechanisms of changes in brain tissue impedance.
> First of all, we should note the changes in electrical resistance that
> occur during excitation. Thus, Arshavsky and Chailakhyan (1966) found that
> at the moment excitation arrives at the cerebellar cortex, a decrease in
> impedance is observed, reaching 6%, comparable in duration to the evoked
> response.
> Salambhos and Weilhui (1968), with adequate stimulation of the subcortical
> nuclei, found that short-term shifts in electrical resistance occur in
> parallel with evoked potentials in the corresponding nuclei. Both evoked
> responses have the same latent period and similar duration.
> Unlike evoked potentials, resistance shifts are not multiphasic, but
> consist of a sharp decrease in resistance and a slow recovery, sometimes
> followed by a slight increase in resistance.
> These shifts change little under the influence of barbiturates; a
> characteristic dependence of the shift amplitude on frequency is observed.
> According to the data of Gaiambhos and Weilu, in the cerebral cortex this
> phenomenon is expressed more weakly.
> By analogy with evoked potentials, the authors called the observed
> phenomenon "evoked resilience." It is likely based on a decrease in the
> membrane resistance of neurons during synaptic activation or impulse
> activity.
> During excitation of nervous tissue, along with short-term shifts,
> longer-term resistance shifts lasting tens of seconds are also observed.
> Thus, Abeu, Kado, Piu, and Amaier (1962, 1965), while measuring resistance
> in the cat's hippocampus, noted a decrease in the active and reactive
> components of resistance in response to auditory and tactile stimulation.
> Loud noise caused a 2% decrease in resistance in the active component and
> a 10% decrease in the reactive component. Touching the paw produced a
> response of significantly greater amplitude (6 and 20%, respectively).
> Habituation to repeated stimuli was observed, expressed in a progressive
> decrease in evoked resistance shifts. Kostenbuch, (Sara Katoz) (1966)
> observed a reversible increase in electrical resistance in the areas
> adjacent to the stimulated brain region in response to electrical
> stimulation of the cortex's surface. The response was inconsistent; changes
> of the opposite sign, i.e., a decrease in resistance, could also be
> observed.
> Aladzhalova (1962) noted an increase in resistance and capacitance in the
> upper layers of the cortex after stimulation of subcortical structures.
> According to her, increased cortical excitability of various origins is
> associated with an increase in cortical resistance, and the appearance of
> excitation is associated with oscillatory changes in resistance against the
> background of growth.
> Birdsworth, Carretta (1966) observed changes in electrical resistance in
> the sympathetic ganglion in response to afferent stimulation. The response
> consisted of a phase of decreased resistance (by 1%) lasting several
> seconds and a phase of increase (by 1-3%) lasting 1-5 minutes. The authors
> Monitored the blood supply to the brain tissue and demonstrated that it was
> not the cause of the induced resistance shifts. They attributed the phase
> of decreasing resistance to a decrease in the membrane resistance of
> neurons during synaptic activation and spike excitation. The phase of
> increasing resistance, they believed, was due to the movement of chlorides
> into the cells, resulting in osmotic hydration of the cells and a reduction
> in the intercellular space.
> In connection with the analysis of the causes of long-term changes in
> electrical resistance, the results of Awaker and Takepack (1965) are of
> interest. They showed that glial membranes can respond to electrical
> stimulation with conductivity shifts lasting tens of seconds.
> Nervous tissue is sensitive to mechanical damage. For example, Burs and
> Carregaal (1966) observed that upon insertion of an electrode, resistance
> can sometimes drop by 2-4%, after which it slowly increases over 15 minutes
> and reaches its initial value. The sensitivity of nervous tissue to damage
> was also noted by
> Abeu, Kado, and HuaNer (1965).
> A number of localized influences associated with the occurrence of waves
> of spreading depression lead to an increase in the electrical resistance of
> the brain."
>
>
> If anyone is interested in this book, I can send you a pdf (5 MB).
>
> > 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.
> >
>