Cav2p3_MA2020_GoC

class braincell.channel.Cav2p3_MA2020_GoC(size, g_max=Quantity(0., 'mS / cm^2'), temp=Quantity(307.15, 'K'), name=None)

Golgi cell Cav2.3 R-type, medium-threshold calcium current.

The Cav2.3 (R-type) medium-threshold calcium current of the cerebellar Golgi cell model of (Masoli et al., 2020) [3]. Its kinetics are those of the car mechanism of the CA1 pyramidal cell model of (Poirazi, Brannon & Mel, 2003) [1] [2], reused unchanged for the Golgi cell. Gating is \(m^3 h\) with voltage-independent time constants and an ohmic driving force:

\[\begin{split}\begin{aligned} I_{Ca} &= g_{max} \, m^3 h \, (E_{Ca} - V) \\ m_\infty &= \frac{1}{1 + \exp((V' + 48.5) / -3)} \\ h_\infty &= \frac{1}{1 + \exp((V' + 53) / 1)} \\ \tau_m &= 50 \ \mathrm{ms}, \quad \tau_h = 5 \ \mathrm{ms} \end{aligned}\end{split}\]

where \(V' = V / \mathrm{mV}\). Neither gate declares a Q10 or a phi, so no temperature factor is applied to either time constant.

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 0.0 mS/cm2, matching the mod file’s gcabar = 0 (mho/cm2), so the mechanism contributes no current until a cell model sets it (see Notes).

• temp (Array | ndarray | bool | number | bool | int | float | complex | Quantity) – Absolute temperature. Accepted and stored, but read by no method of this class (see Notes). Defaults to 34 degrees Celsius, matching the mod file’s celsius = 34.

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

See also

CaHVA_MA2020_GoC

The Golgi cell model’s other high-voltage-activated calcium current, from a different origin.

braincell.channel._base.OhmicHH

Template supplying the ohmic driving force used above.

Notes

Ported from GoC/channel/Cav2p3_MA20_GoC.mod, whose TITLE reads “Ca R-type channel with medium threshold for activation” and whose header records that the mechanism is “used in distal dendritic regions, together with calH.mod”, that it “uses channel conductance (not permeability)”, that it was “written by Yiota Poirazi on 11/13/00” and that BrainCell renamed it “From car to Cav2_3”. The Poirazi credit is unusual among these cerebellar imports in naming an author of the origin papers rather than an unrelated porter, but it is still not turned into a citation on its own: entries [1] and [2] below are the published records. The upstream car.mod and its sibling calH.mod are both files of ModelDB accession 20212, the shared CA1 pyramidal model deposit serving the two companion papers; because the mechanism belongs to that shared biophysics and cannot be assigned to one paper, both are cited.

Import deviation – interpolation table removed. The original TABLE directive tabulated the indexed inf and tau arrays over [-100, 100] mV; NEURON clamped to the boundary value outside that range, so any BrainCell/NEURON divergence outside that window is expected. BrainCell evaluates the formulas per call instead.

The indexed rate structure was split into named methods. The mod file stores its steady states and time constants in inf[2] and tau[2], filled by a FROM i=0 TO 1 loop over the helpers varss(v, i) and vartau(v, i). Index 0 is activation and index 1 is inactivation, per the mod file’s own trailing comments and its INITIAL block, which assigns m = inf[0] and h = inf[1]. BrainCell therefore maps index 0 onto f_m_inf() / f_m_tau() – the (v + 48.5) / -3 curve with tau = 50 – and index 1 onto f_h_inf() / f_h_tau() – the (v + 53) / 1 curve with tau = 5. Both branch values were read back against the mod file’s if (i==0) / else if (i==1) arms.

The default conductance is genuinely zero. The mod file’s gcabar = 0 (mho/cm2) is commented “initialized conductance”: the deposit expects the cell-setup code to assign a density per region, and BrainCell carries the same zero. This is not a missing value or a failed unit conversion.

temp is accepted, stored on the instance and never read. Neither Gate carries a q10 or a phi, and this mechanism has no GHK term, so nothing in the class consumes a temperature. The mod file likewise declares celsius = 34 without using it in any rate expression.

The mod file’s eca = 140 (mV) is not read by this class: the reversal potential is supplied by the attached Calcium ion object. Its gmax running-maximum diagnostic, updated in BREAKPOINT by if (g > gmax) { gmax = g }, is a monitoring variable that never feeds the current, and BrainCell drops it.

NEURON’s raw ica here is g * (v - eca), i.e. outward-positive; OhmicHH computes g_max * m^3 h * (E - V), the same current under BrainCell’s repo-wide inward-positive convention.

The mod file is already cnexp upstream, so no derivimplicit -> cnexp substitution was made for it, and the MA2020 tables record no rate-refresh relocation and no NMODL default-precision rewrite for this mechanism.

References

[1] (1,2)

Poirazi, P., Brannon, T., & Mel, B. W. (2003). Arithmetic of subthreshold synaptic summation in a model CA1 pyramidal cell. Neuron, 37(6), 977-987. doi:10.1016/S0896-6273(03)00148-X

[2] (1,2)

Poirazi, P., Brannon, T., & Mel, B. W. (2003). Pyramidal neuron as two-layer neural network. Neuron, 37(6), 989-999. doi:10.1016/S0896-6273(03)00149-1

[3]

Masoli, S., Ottaviani, A., Casali, S., & D’Angelo, E. (2020). Cerebellar Golgi cell models predict dendritic processing and mechanisms of synaptic plasticity. PLOS Computational Biology, 16(12), e1007937. doi:10.1371/journal.pcbi.1007937

root_type

alias of Calcium