1. A computational node comprising: input signal lines connected through memristive, nanowire-junctions to one or more input-providing computational nodes; an output signal line connected through memristive, nanowire-junctions to one or more output-receiving computational nodes; a leaky integrator that integrates input signals received through the input signal lines and the output signal line; a thresholder that compares leaky-integrator output to a threshold value; a clock input; and a state machine that, based on received thresholder output and clock input, directs state transitions and that generates computation-node spike signals, wherein spike signals include forward spikes output on the output signal line and backward spikes output on the input signal lines.