The name is absent

129

into input to a branched model neuron is easy because the input terms look much
like currents from ion channels. On branch b the synaptic current from receptors of
type Q is given by

s_b

IbQ<^, i) = 52 GQr_bsQ{t)δ(x - x_bs) (v⅛ - Eq) ,              (5.2)

where Gq is the maximal conductance, and Eq is the reversal potential of that re-
ceptor. One notable exception to this form of synaptic current is the NMDA current
because it is voltage-dependent, a fact that poses an extra problem for model reduc-
tion.

5.1.1 Reduction of the NMDA Magnesium Block Term

The NMDA receptor is governed by a magnesium block that is in the bound state
when the voltage is close to rest. When there is sufficient depolarization, Mg²⁺ is
unbound from the receptor and this permits a larger synaptic current to flow. Hence
the NMDA synaptic current has the form

Sb

Λ>,NMDa(^> t) — 52 G^fNMDA'^rbs,NMDA(t)Bb(v_b)δ(x — X_bs) (v_b ~ ¾IMDa) )      (5.3)

s=l

where

^Bb^ ~ 1 + exp(-0.062u_b)[W²⁺]_o∕3.57

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