Figure 2.

Illustration of the learning rule. The weight change dw/dt is plotted as a function of the post- and presynaptic firing rate for fixed pre- (left) or postsynaptic (right) rates. The gray, dashed line shows the rule that we use for inhibitory connections and whose threshold for LTP, in contrast to excitatory connections, does not depend on the presynaptic rate. The black line marks the transition between LTD and LTP. In this example, the parameters of the learning rules were set to Θ_exc = 6 Hz, Θ_inh = 18 Hz, A_exc = 2, w_max = 4, and the weight value was fixed at w_max/3 for excitatory and w_max/2 for inhibitory connections.