<p>The
lamprey is one of the most ancient of extant vertebrate species. It has changed relatively little in 450
million years and is considered a prototype for all vertebrates. Its primitive nervous system has been studied
extensively, and the basic architecture of the central pattern generator (CPG)
that produces its anguilliform swimming motion is well known. Here
it is shown that each segmental component of the lamprey's CPG is a JK
flip-flop, with additional excitatory inputs and feedback that cause all of the
neurons' states to oscillate. The JK
flip-flop is the most widely used flip-flop design in electronic computational
systems because of its advantageous features.
This is apparently the first discovery that a known network of neurons functions
as a logic circuit. The lamprey's oscillator
can be implemented with electronic hardware, and the design is apparently
unknown in engineering. A
simulation based on simple neuron responses to excitation and inhibition illustrates
the common period, phase relationships, and burst durations of the segmental
cells' oscillations. Simulation software
for electronic logic circuits verifies the simulated neuron responses, on vastly
different time scales. The simulation
methods presented here may aid in further study of CPG neurophysiology. The architecture of the oscillating JK
flip-flop may aid in the development of artificial neural network applications
such as robotics.</p>