1. A system comprising a non-transitory machine-readable medium having computer-executable instructions for performing a method to simulate activity recorded from an interface to nerve fibers, the method comprising: simulating generation of at least one signal of a variable capable of being recorded by an interface to nerve fibers; simulating translation of the variable to motor neuron firing; generating a realistic simulated neural recording that corresponds to how a real body would respond to motor neuron stimulus of the nerve fibers; and simulating recording of the motor neuron firing by the interface to nerve fibers, wherein the simulated activity is neural activity, and wherein simulating recording of the motor neuron firing comprises: generating a virtual electrode; mapping the motor neuron firing to signals of the virtual electrode by a mapping matrix B; and multiplying a cross-talk matrix C and the mapping matrix B.