REVIEW 4 major objections 4 minor 23 references
Is K+ current in Action Potential real?
T0 review · 4 major / 4 minor · reviewed 2026-08-04 · deepseek-v4-flash
Pith's one-line read The paper argues that the delayed potassium current is a voltage-clamp artifact, and that action-potential repolarization is a capacitive current through a series RC circuit built on the axon initial segment.
desk verdict Original but internally inconsistent: the paper claims HH's K+ current is a clamp artifact and the AP undershoot is capacitive, yet the series RC circuit it defines cannot produce a negative phase. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The central object is a reinterpretation of the neuron as a serially connected RC oscillator rather than the parallel RC circuit of the classical model. In this circuit the membrane acts as the capacitor and the axon initial segment – the specialized region where the axon leaves the cell body – acts as the series resistor. The key identity is the differentiator relation V_out = RC dV_in/dt, in which the output voltage across the AIS resistance changes sign for rising versus falling input edges. That sign reversal produces the hyperpolarization that a parallel circuit cannot explain, removing the need for an injected delayed current in the opposite direction. A second mechanism is the elastic
What would settle it
A decisive test would be to record from an intact, unclamped neuron with a potassium-selective microelectrode placed near the soma membrane while the action potential is elicited by natural synaptic input; if a delayed rise in extracellular potassium tracks the falling phase, the artifact claim fails. Equivalently, ablating or blocking the AIS should abolish the normal hyperpolarization if the serial-RC explanation is right.
Extended reading notes
Core claim
The central claim, stated on the author's terms, is that the potassium current seen in the classic voltage-clamp recordings is real enough, but it is not the natural repolarizing current. When the membrane is suddenly depolarized and held at a fixed voltage, the neuron cannot restore its original concentrations, so it rebalances by releasing potassium through the membrane; that artificial efflux is what physiologists recorded and interpreted as a delayed current. In a native action potential no clamp holds the voltage, and the neuron instead discharges the excess sodium that entered during the rising phase, sending it through the axon initial segment. The falling phase is therefore the capac
Load-bearing premise
The load-bearing premise is that during the transient phase nearly all significant membrane current flows serially through the axon initial segment, so the distributed non-gated membrane channels can be neglected as a parallel pathway; if the AIS is not the sole series path, or if voltage-gated channels contribute to repolarizing current, the capacitive-current explanation collapses.
Editorial extensions
If this is right
- If the delayed potassium current is a clamping artifact, the native action potential contains no delayed outward potassium phase; repolarization is a capacitive current that reverses direction when the membrane voltage begins to fall.
- The serial-RC topology predicts that the geometry and resistance of the axon initial segment set the shape and time course of the falling phase, so interventions that alter AIS conductance should change the action-potential waveform in a specific way.
- Because the membrane oscillation is damped and largely reversible, the action potential stores most of its energy as elastic potential energy rather than dissipating it, directly explaining the measured heat absorption and the absence of significant net heat production.
- In unclamped neurons, the excess sodium that enters during depolarization is predicted to leave mainly through the AIS rather than across the soma membrane, so the delayed rise in extracellular potassium near the soma should be absent during natural firing.
- The model implies that protein-controlled delayed potassium channels are not required for the falling phase, which would motivate a re-examination of their role in normal signaling.
Reading between the lines
- Editorial inference: If repolarization is capacitive and largely reversible, the metabolic cost per action potential may be lower than classical current-based estimates, so models of brain energy consumption and oxygen use would need recalibration.
- Editorial inference: The serial-RC mechanism yields a testable relationship between AIS anatomy (length, diameter, channel density) and the time constant of repolarization; comparing waveforms across neuron types with known AIS morphology could confirm or refute it.
- Editorial inference: Because the artifact emerges specifically under voltage clamp, pharmacology studies that use clamp-measured currents to infer native channel function may misattribute the clamping-induced potassium release to normal physiology; translating those dose-response relationships to intact tissue warrants caution.
- Editorial inference: The elastic/soliton view of propagation suggests that mechanical properties of the axon, such as stiffness or tension changes with myelination or injury, could affect conduction velocity independently of membrane resistance; this opens a mechanical axis for studying nerve dysfunction.
Signed reviews
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper argues that the delayed K+ current in the Hodgkin–Huxley (HH) action-potential (AP) model is an experimental artifact. It claims that the AP is produced by a serially connected RC circuit in which the resistance is the axon initial segment (AIS), and that the membrane's capacitive current, not a delayed K+ efflux, explains AP hyperpolarization. The outward K+ current measured under voltage clamp is reinterpreted as a clamping-induced concentration adjustment. The paper also proposes an elastic membrane oscillation, with AP(t)=A e^(−δt) e^(−ζt) cos(ωt), as the dominant AP-shaping process.
Significance. If correct, this would overturn a central pillar of cellular neuroscience: the AP repolarization mechanism and the existence of a physiological delayed K+ conductance. The paper also claims to resolve the long-standing reversible heat-production anomaly. However, the manuscript provides no quantitative fit to any AP recording, relies almost entirely on the author's own prior papers for its physical foundations, and contains a basic internal inconsistency: the series RC circuit in Eqs. (1)–(3) cannot produce the negative voltage phase that defines hyperpolarization, while the negative phase in Fig. 2 is introduced by an ad hoc elastic term. The manuscript therefore does not meet the evidentiary standard for a paradigm-changing claim.
major comments (4)
- [§4.2, Eqs. (1)–(3) and Fig. 2] The central mechanism is internally inconsistent. In a series RC circuit excited by a 'sudden jump followed by a discharge,' the capacitor voltage V_C(t) is non-negative and monotonically decaying (or a sum of such terms); it never produces the negative phase required for AP hyperpolarization. Eq. (1) gives the voltage across the series resistor, which is a differentiator output, not the membrane potential. The negative undershoot in Fig. 2 comes solely from the ad hoc elastic factor e^(−ζt) cos(ωt) introduced in §4.3, not from the RC circuit. Thus the paper's claim that the capacitive current 'perfectly describes the so-called hyperpolarization' is contradicted by its own equations.
- [§4.3 and Appendix A] The quantitative basis is circular and underdetermined. The AP waveform is imposed as A e^(−δt) e^(−ζt) cos(ωt), with δ=ζ=0.34 set by hand; no fitting to experimental AP records is shown. The abstract's claim of a 'perfect description' is contradicted by §4.3's own admission that the model 'may not be perfect' and Appendix A's caveat that the force estimates 'may not be exact.' The physical derivation refers to the author's prior works ([5], [6], [12]) for the 'correct' equations, while the voltage-clamp reinterpretation in §5.1 depends on concentration values and Nernst surface taken from Table 1 of [6]. This makes the central claim unfalsifiable as presented.
- [§5.1–5.2] The clamping argument is internally inconsistent. The paper states that under clamping a genuine K+ outward current does flow through the membrane, appearing after a delay because of concentration-layer dynamics. That is exactly the phenomenon HH measured. The difference between native and clamped APs is asserted, not derived: the paper gives no mechanism by which AIS Na+ efflux restores the resting potential without a repolarizing current, nor any account of the AP undershoot beyond the unproven elastic term. The statement that Na+ and K+ currents 'cannot cause hyperpolarization' because they flow in different paths mischaracterizes the HH claim, which is that the K+ current is the repolarizing current, not that it interferes with Na+ current.
- [§3 and §4.2] The load-bearing assumption that the AIS is the sole significant transient current path is asserted, not derived. Section 4 states that the distributed resting ion channels 'play a role only in the resting state' and that the AIS conductance is 'about two orders of magnitude higher,' but no quantitative model of the distributed channels or justification for neglecting them during the transient is provided. If part of the repolarizing current flows through distributed non-gated or voltage-gated channels, the serial RC model collapses. This is a necessary condition for the paper's artifact claim, so the paper's conclusion is unsupported even before the RC inconsistency above.
minor comments (4)
- [Fig. 2] The caption states δ=0.34, but the plot includes a curve labeled 'Action Potential, δ=0.2'; the legend needs clarification. The x-axis is in arbitrary units, but the text in §4.2 discusses microsecond and millisecond scales; the figure should specify the time scale.
- [§5.1] The paper uses 'Rest' at −21 mV and remarks that HH measured 42.5 mV, but this calculation is not connected to the actual squid axon experimental values; adding the reference and a formula would improve reproducibility.
- [§3 and §4.4] The term 'Adenozine triphosphate' should be 'Adenosine triphosphate'; the sentence 'The research did nor receive any support' contains a typo.
- [References] Several load-bearing references are the author's own unpublished or in-review works ([5], [6], [12], [13], [14]); a journal referee cannot verify these. This is not a presentation issue alone, but it compounds the circularity. Also, reference [4] appears to have an incorrect volume/article number.
Circularity Check
The AP hyperpolarization is called capacitive current by definition, and the serial-RC/elastic model carrying the K+-artifact claim is imported from the author's own unpublished/preprint papers.
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self definitional
[§4.2 (after Eq. 3); used again in §4.3/Fig. 2]
"the capacitive current, which by definition changes its direction and so generates an opposite voltage on the resistor represented by the AIS, perfectly describes the so-called "hyperpolarization". It is not the effect of a K+ current through the membrane: the resting ion channels do not have sufficient conductance."
The central inference is that hyperpolarization is the capacitive current because a capacitor current reverses when the voltage falls. That is the definition I = C dV/dt, not a derived result. The RC equations (1)-(3) do not generate the AP; the negative phase of the AP is imported separately in §4.3 as AP(t)=A e^{-δt} e^{-ζt} cos(ωt). Calling the falling edge 'capacitive current' therefore reduces to renaming the input waveform's decline; it does not predict it.
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self citation load bearing
[Introduction and §4.2]
"The correct physical explanation can be derived using the unified model of neuronal operation 5,6: under the mechanical pressure caused by the mutual repulsion of the ions, the electrolyte is compressed and expanded. ... For the physical and mathematical description, see section 4 in 12; for its algorithmic specifics13, for further details14."
The serial-RC oscillator and the elastic-gradient model on which the K+-artifact claim depends are not derived here; they are referred to refs. [5,6,12], all authored by V\'egh, including an 'in review' preprint [5] and an arXiv preprint [6]. These self-citations are load-bearing because no independent derivation, external benchmark, or formal proof is given for the 'correct physical explanation'. Under hard rule 4, these are not independent support.
1 more flagged steps
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ansatz smuggled in via citation
[§4.3]
"The rush-in of Na+ ions results in electric, chemical, and elastic gradients, see6. ... The elastic force is described by the F(t)=F max elastic × e −ζ∗t × cos(ω∗t) formula. The classical model entirely neglects this elastic gradient."
The elastic oscillatory term is the source of the negative/undershoot phase in Fig. 2; it is introduced by ansatz and its physical basis is justified only by citing the author's own paper [6]. The parameters δ=ζ=0.34 are set in Fig. 2, and then this damped cosine is presented as the explanation of the AP shape ('explaining why the damped elastic oscillation almost perfectly describes the time course of the AP'). This is a chosen/fitted ansatz, not a derivation from the RC model.
full rationale
The paper's central claim is that the delayed K+ current is an artifact and that the AP hyperpolarization is the capacitive current of a serial RC circuit. The derivation chain reduces at two key points. First, the identification of hyperpolarization with capacitive current is made by definition ('capacitive current, which by definition changes its direction ... perfectly describes the so-called hyperpolarization'), and the actual negative phase of the AP is supplied separately by an ad hoc elastic term e^{-ζt} cos(ωt) from §4.3, not by the RC equations. Second, the physical basis of the serial-RC model and the elastic-gradient model is deferred to the author's own prior works [5,6,12], including an in-review preprint and an arXiv preprint, with no independent derivation in this manuscript. These self-citations are load-bearing because the K+-artifact conclusion depends entirely on accepting that unreviewed model. I am not judging whether the HH framework is correct; under the circularity standard, however, the paper's central result is forced either by definition or by a self-citation chain, which corresponds to a score of 8.
Assumptions & free parameters
free parameters (6)
- δ (discharge decay constant) =
0.34 (arb. u.)
- ζ (elastic damping constant) =
0.34 (arb. u.)
- ω (damped oscillation frequency) =
not specified (arb. u.)
- R_AIS (axon initial segment resistance) =
not given
- C (membrane capacitance) =
not given
- N_rush_in (~number of Na+ ions entering) =
≈10^7
assumptions (5)
- domain assumption During the transient state, the AIS is the only significant current path and distributed non-gated channels are negligible.
- domain assumption A neuron's electrical behavior during AP is a capacitor in series with a resistor (the AIS), not in parallel.
- ad hoc to paper The AP waveform is the product of two exponentials and a cosine: e^(−δt)e^(−ζt)cos(ωt), with the elastic and discharge mechanisms superposed independently.
- ad hoc to paper Physics for living nature differs from 'laws valid for inanimate nature' in a way that makes this model correct.
- domain assumption The Na-K pump stops at AP onset and excess Na+ can only leave via the AIS current.
invented entities (1)
-
AIS as a single series resistor carrying all transient membrane current
Cite this review
Pith. "Pith review of Is K+ current in Action Potential real?." pith.science (2026). https://pith.science/paper/IZIIQ44F
@misc{pith2026260800654,
author = {Pith},
title = {Pith review of: Is K+ current in Action Potential real?},
year = {2026},
howpublished = {\url{https://pith.science/paper/IZIIQ44F}},
note = {Machine review of arXiv:2608.00654}
}
read the original abstract
The correct description of ion traffic during an Action Potential in neurons has fundamental importance from its theoretical description to practical clinical applications. The classical Hodgkin-Huxley theory hypothesized that a delayed K+ current causes the hyperpolarization of the Action Potential. The paper shows that the membrane's capacitive current was misinterpreted as K+ current, and that the direct evidence for that current is an experimental artifact, both arising from an incomplete understanding of the electrical model. After introducing the Axon Initial Segment (discovered decades after constructing the classical model) and using the correct cross-disciplinary physical laws for living nature (instead of using laws valid for inanimate nature), one can construct the correct model for neuronal operation, which provides the perfect description of neuronal operation, including the Action Potential, in full accordance with the laws of science.
Figures
Figures from the paper (1 more)
Reference graph
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Reviewed August 4, 2026 · model on record in the stance chip above.
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