Contribution of Axons to Short-Term Dynamics of Neuronal Communication

Axons are traditionally viewed as faithful transmission lines of the neural code, that is, they are thought to propagate temporal patterns of action potentials generated at the proximal part of the neuron with little degradation to distal presynaptic sites. However, axonal membrane excitability can be far more complex than usually credited. In consequence, action potential conduction velocity can change dependent on prior activity and therefore alter temporal patterns during propagation. In some cases, axons can fail to propagate action potentials or elicit additional ones at distal locations. Furthermore, changes in excitability can alter action potential shape, with consequences for presynaptic transmitter release. Finally, these properties can be subject to neuromodulation, as many axons express both metabotropic and ionotropic receptors in nonsynaptic membrane. This chapter highlights some of the aspects of axonal dynamics and their potential role for neural computations.