The molecular mechanisms underlying the temporal plasticity (temporal tuning) of cortical cells remain controversial. Experimental observations indicate that the neuronal responses at the primary auditory cortex are affected by behavioral learning. In this paper, we present a minimal feed-forward model of the primary auditory cortex, based on the dynamic synapse and the leaky integrate-and-fire neuron models, in order to search for the origin of the observed plasticity. We demonstrate that the frequency response of the model is markedly modified by regulating the contribution of synaptic facilitation to the short-term dynamics of synapses (U(1)). Consequently, we propose that the variation of this parameter may be responsible for primary auditory cortex enhancement achieved by behavioral training. Based on our model, we assume that the contribution of facilitation arises from the amount of Ca(2+) influx each time an action potential arrives at the nerve terminal. Regardless of what really leads to the long-term variation of Ca(2+) influx, we suggest that this process is responsible for the temporal tuning of responses observed in experimental studies. We believe that measurement of the long-term variation of Ca(2+) influx at the pre-synaptic area of the cortical cells in auditory learning trials would be the first step to validate our hypothesis.