DA dependent STDP modulates the Cxe-CD synaptic efficiency. The first raise of DA level is due to the expectation of reward and the second is due to reward delivery. In this trial, the reward delivery increases the Cxe-CD synaptic efficiency via STDP. The top four panels(from top to bottom) are spike trains of cortical network, caudate nucleus, substantia nigra pars reticulata, and superior colliculus; the fifth and sixth are the efficiency of Cxe-CD synapses and the dopamine level in a trial.