Neural coding:: Hybrid analog and digital signalling in axons

Mammalian axons are thought to act as digital signaling devices, conveying information only by the timing and rate of all-or-none action potentials. Two recent studies now show that synaptic potentials can also spread far down the axon and influence action potential-triggered transmitter release in a graded, 'analog' manner. Axons; thus encode information both about subthreshold and suprathreshold synaptic activity.