COMMENT by Johannes Luthman: Based on NEURON 6.0's built-in exp2syn.mod. Changes made to the original: * tau1 renamed tauRise; tau2, tauFall * restructuring of NEURON block * microsiemens changed to siemens for consistency with the other NMODLs. Original comment: Two state kinetic scheme synapse described by rise time tauRise, and decay time constant tauFall. The normalized peak condunductance is 1. Decay time MUST be greater than rise time. The solution of A->G->bath with rate constants 1/tauRise and 1/tauFall is A = a*exp(-t/tauRise) and G = a*tauFall/(tauFall-tauRise)*(-exp(-t/tauRise) + exp(-t/tauFall)) where tauRise < tauFall If tauFall-tauRise -> 0 then we have a alphasynapse. and if tauRise -> 0 then we have just single exponential decay. The factor is evaluated in the initial block such that an event of weight 1 generates a peak conductance of 1. Because the solution is a sum of exponentials, the coupled equations can be solved as a pair of independent equations by the more efficient cnexp method. ENDCOMMENT NEURON { POINT_PROCESS DCNsyn NONSPECIFIC_CURRENT i RANGE g, i, e, tauRise, tauFall } UNITS { (nA) = (nanoamp) (mV) = (millivolt) } PARAMETER { tauRise = 1 (ms) tauFall = 1 (ms) e = 0 (mV) } ASSIGNED { v (mV) i (nA) g (microsiemens) factor } STATE { A (microsiemens) B (microsiemens) } INITIAL { LOCAL tp if (tauRise/tauFall > .9999) { tauRise = .9999*tauFall } A = 0 B = 0 tp = (tauRise*tauFall)/(tauFall - tauRise) * log(tauFall/tauRise) factor = -exp(-tp/tauRise) + exp(-tp/tauFall) factor = 1/factor } BREAKPOINT { SOLVE state METHOD cnexp g = B - A i = g*(v - e) } DERIVATIVE state { A' = -A/tauRise B' = -B/tauFall } NET_RECEIVE(weight (microsiemens)) { state_discontinuity(A, A + weight*factor) state_discontinuity(B, B + weight*factor) }