Sensory processing requires mechanisms of fast coincidence-detection to discriminate synchronous from asynchronous inputs. Spike-threshold adaptation enables such a discrimination but is ineffective in transmitting this information to the network. We will discuss unpublished results showing that axonal sodium channels read and transmit precise levels of input synchrony to the postsynaptic cell by modulating the presynaptic action potential (AP) amplitude. In consequence, synaptic transmission is facilitated at connected pairs of L5-L5 synapses when the presynaptic spike is produced by synchronous inputs. Using dual soma-axon whole-cell recordings, calcium imaging, and computer modeling, we show that this facilitation results from enhanced AP amplitude in the axon due to minimized inactivation of sodium channels in the axon. Quantifying global network activity, we found that this process facilitates propagation of synchronous input-mediated spiking activity in local brain circuits and may therefore constitute a powerful code for neuronal computation.