hh_psc_alpha_gap – Hodgkin-Huxley neuron model with gap-junction support
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Description
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``hh_psc_alpha_gap`` is an implementation of a spiking neuron using the
Hodgkin-Huxley formalism. In contrast to ``hh_psc_alpha`` the implementation
additionally supports gap junctions.

1. Postsynaptic currents
Incoming spike events induce a postsynaptic change of current modelled
by an alpha function. The alpha function is normalized such that an event of
weight 1.0 results in a peak current of 1 pA.

2. Spike Detection
Spike detection is done by a combined threshold-and-local-maximum search: if
there is a local maximum above a certain threshold of the membrane potential,
it is considered a spike.

3. Gap Junctions
Gap Junctions are implemented by a gap current of the form
:math:`g_{ij}( V_i - V_j)`.

See also [1]_, [2]_, [3]_, [4]_.

Parameters
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The following parameters can be set in the status dictionary.

===========  ====== ============================================================
tau_ex       ms      Rise time of the excitatory synaptic alpha function
tau_in       ms      Rise time of the inhibitory synaptic alpha function
g_K          nS      Potassium peak conductance
V_m          mV      Membrane potential
E_L          mV      Leak reversal potential
g_L          nS      Leak conductance
C_m          pF      Capacity of the membrane
tau_syn_ex   ms      Rise time of the excitatory synaptic alpha function
tau_syn_in   ms      Rise time of the inhibitory synaptic alpha function
E_Na         mV      Sodium reversal potential
g_Na         nS      Sodium peak conductance
E_K          mV      Potassium reversal potential
g_Kv1        nS      Potassium peak conductance
g_Kv3        nS      Potassium peak conductance
Act_m        real    Activation variable m
Inact_h      real    Inactivation variable h
Act_n        real    Activation variable n
I_e          pA      External input current
===========  ====== ============================================================

References
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.. [1] Gerstner W, Kistler W. Spiking neuron models: Single neurons,
       populations, plasticity. Cambridge University Press
.. [2] Mancilla JG, Lewis TG, Pinto DJ, Rinzel J, Connors BW (2007).
       Synchronization of electrically coupled pairs of inhibitory
       interneurons in neocortex, Journal of Neurosciece, 27:2058-2073
       DOI: https://doi.org/10.1523/JNEUROSCI.2715-06.2007
       (parameters taken from here)
.. [3] Hodgkin AL and Huxley A F (1952). A quantitative description of
       membrane current and its application to conduction and excitation in
       nerve. The Journal of Physiology 117.
       DOI: https://doi.org/10.1113/jphysiol.1952.sp004764
.. [4] Hahne J, Helias M, Kunkel S, Igarashi J, Bolten M, Frommer A, Diesmann M
       (2015). A unified framework for spiking and gap-junction interactions
       in distributed neuronal netowrk simulations. Frontiers in
       Neuroinformatics, 9:22. DOI: https://doi.org/10.3389/fninf.2015.00022

Sends
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SpikeEvent, GapJunctionEvent

Receives
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SpikeEvent, GapJunctionEvent, CurrentEvent, DataLoggingRequest

See also
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:doc:`Neuron <index_neuron>`, :doc:`Current-Based <index_current-based>`, :doc:`Hodgkin-Huxley <index_Hodgkin-Huxley>`, :doc:`Gap Junction <index_gap junction>`