Under physiological conditions, a nerve action potential (AP) is generated at one end of an axon and proceeds towards its other end. Electrical nerve stimulation of an axon normally produces two propagating APs, one in the orthodromic direction (towards the terminal end where the neurotransmitter is released) and one propagating in the antidromic direction (towards the soma). Techniques have been developed to prevent the AP from propagating in one of these directions, while allowing it to travel in the other. Such unidirectionally propagating APs can be used for collision block of naturally incoming nerve signals to a target. This may be of clinical utility in conditions of spasticity of skeletal muscles or in preventing undesirable sensory inputs. They can be directed towards the target (orthodromic) without activating the soma and resulting central reflexes.