Synaptic noise and other sources of randomness in motoneuron interspike intervals.

tance information transmission in the nervous system is accomplished by the propagation of all-or-none spikes along axons, and further that this information is carried in a single axon by the timing of spikes. When a neuron is dis-charging with a constant mean frequency, in-formation is probably contained in the length of interspike intervals which, however, are notoriously variable. Much recent attention has been focused on the statistics of this vari-ability. In part, this interest has reflected a concern for the accuracy of nervous system function (interval variability, from this point of view, represents noise in the signal being transmitted (8)), but perhaps a larger body of