CaHVA_MA2020_GrC

class braincell.channel.CaHVA_MA2020_GrC(size, g_max=Quantity(0.46, 'mS / cm^2'), temp=Quantity(303.15, 'K'), name=None)

Granule cell high-voltage-activated calcium current.

The high-voltage-activated (HVA) calcium current of the cerebellar granule cell model of (Masoli et al., 2020) [2], whose kinetics are those of the earlier granule cell model of (D’Angelo et al., 2001) [1]. Gating is \(s^2 u\) in alpha/beta form with an ohmic driving force:

\[\begin{split}\begin{aligned} I_{Ca} &= g_{max} \, s^2 u \, (E_{Ca} - V) \\ \alpha_s &= 0.04944 \exp((V' + 29.06) / 15.873) \\ \beta_s &= 0.08298 \exp((V' + 18.66) / -25.641) \\ \alpha_u &= 0.0013 \exp((V' + 48) / -18.183) \\ \beta_u &= 0.0013 \exp((V' + 48) / 83.33) \end{aligned}\end{split}\]

where \(V' = V / \mathrm{mV}\) and the rates are per millisecond. Both gates are further scaled by gate_phi() with \(Q_{10} = 3\) referred to 20 degrees Celsius (see Notes).

Parameters:

• size (int | Sequence[int] | integer | Sequence[integer]) – Channel state shape.

• g_max (Array | ndarray | bool | number | bool | int | float | complex | Quantity | Callable) – Maximal conductance density. Defaults to 0.46 mS/cm2, the mod file’s gcabar = 0.00046 mho/cm2 (see Notes).

• temp (Array | ndarray | bool | number | bool | int | float | complex | Quantity) – Absolute temperature driving the gates’ Q10 factor. Defaults to 30 degrees Celsius, matching the mod file’s celsius = 30.

• name (str | None) – Optional channel name.

See also

CaHVA_MA2020_GoC

The same mechanism imported from the Golgi cell deposit; identical constants, different model citation, and one fewer import deviation (see its Notes).

braincell.channel._base.OhmicHH

Template supplying the ohmic driving force used above.

Notes

Ported from GrC/channel/CaHVA_MA20_GrC.mod. An earlier revision of this docstring named the source file CaHVA_MA20_GrC.mod, which does not exist; the shipped file uses the two-digit year code, and that is corrected here. That file and GoC/channel/CaHVA_MA20_GoC.mod are identical apart from the SUFFIX line, which is why the two BrainCell classes carry the same constants; they are separate classes, not a subclass pair, because they were imported from two different deposits and therefore take two different model citations.

The file’s COMMENT credits “E.D’Angelo, T.Nieus, A. Fontana”, naming authors 1, 2 and 7 of the eight-author origin paper. That credit is not turned into a citation: entry [1] below lists all eight.

The mod file applies its Q10 factor inside each of the four rate functions, as Q10 = 3^((celsius - 20)/10) multiplying alp_s, bet_s, alp_u and bet_u. BrainCell hoists it to the gate level instead, as Gate(q10=3.0, temp_ref=20 degC). For the alpha/beta form the two are algebraically identical: with \(\alpha = Q_{10} a\) and \(\beta = Q_{10} b\), \(\alpha (1 - x) - \beta x = Q_{10} (a (1 - x) - b x)\), which is exactly what phi multiplies. The rate methods here therefore return the unscaled a/b.

The mod file’s eca = 129.33 (mV) is not read by this class: the reversal potential is supplied by the attached Calcium ion object.

Import deviation – interpolation table removed. The original TABLE directive tabulated s_inf, tau_s, u_inf and tau_u over [-100, 30] mV, clamping to the boundary value outside that range; BrainCell evaluates the continuous formulas per call, so any BrainCell/NEURON divergence outside that window is expected.

Import deviation – integration method substituted. The upstream derivimplicit is replaced by cnexp. This is the granule cell mechanism’s one difference in status from its Golgi cell twin, which was already cnexp upstream. The substitution is exact here, because the s and u gate ODEs are independent of one another.

Import deviation – NMODL default-precision rewrite. Kalpha_s is written 15.87301587302 in the mod source and 15.873 here, because BrainCell aligns with the roughly six-significant-figure defaults NEURON’s generated C emits rather than with the source text. Ordinary in-formula literals are not subject to this rewrite and keep their source values.

NEURON’s raw ica here is g * (v - eca), i.e. outward-positive; OhmicHH computes g_max * s^2 u * (E - V), the same current under BrainCell’s repo-wide inward-positive convention.

g_max’s default is the gcabar of the cell-model deposit this mechanism was imported from – a value tuned for that model, not a conductance reported by the origin paper.

References

[1] (1,2)

D’Angelo, E., Nieus, T., Maffei, A., Armano, S., Rossi, P., Taglietti, V., Fontana, A., & Naldi, G. (2001). Theta-frequency bursting and resonance in cerebellar granule cells: experimental evidence and modeling of a slow K+-dependent mechanism. The Journal of Neuroscience, 21(3), 759-770. doi:10.1523/JNEUROSCI.21-03-00759.2001

[2]

Masoli, S., Tognolina, M., Laforenza, U., Moccia, F., & D’Angelo, E. (2020). Parameter tuning differentiates granule cell subtypes enriching transmission properties at the cerebellum input stage. Communications Biology, 3(1), 222. doi:10.1038/s42003-020-0953-x

root_type

alias of Calcium