(*
   Simple Model of Spiking Neurons, Izhikevich  E

   IEEE Transactions on Neural Networks (2003) 14:1569- 1572
 
*) 

component Izhikevich03 =
struct

  binding construct t V U k1 k2 k3 theta a b c d spike tspike Isyn h =

    binding subthreshold_eq = [ 
                                [ d (V t h) =  (k1 * V * V) + (k2 * V) + k3 + (- U) + Isyn ]
                                [ d (U t h) =  a * ((b * V) - U) ]
                              ]

    binding threshold_detect  =  [ spike = (V > theta) ]

    binding tspike_set        =  [ tspike = (if spike then t else tspike) ]

    binding subthreshold_regime  = Diagram.SEQUENCE subthreshold_eq (Diagram.SEQUENCE threshold_detect tspike_set)
		 
    binding refractory_eq        = [ 
                                     [ t      =  t ]
				     [ spike  = false ]
				     [ tspike = tspike ]
				     [ V      = c ]
				     [ U      = (U + d) ] 
                                    ]

    return   Diagram.TRANSIENT subthreshold_regime refractory_eq spike 

end