A Spiral Attractor Network Drives Rhythmic Locomotion in Aplysia

The joint activity of neural populations often contains an embedded low-dimensional signal. Though usually interpreted as the signature of some underlying dynamical system, it is unknown if this is true. By imaging Aplysia’s pedal ganglion during fictive locomotion, we show that its population-wide spiking activity arises from a low-dimensional spiral attractor. Evoking locomotion moved the population from irregular spontaneous activity into a low-dimensional, periodic, decaying orbit – a spiral. The population behaved as a true attractor, converging to the same orbit when evoked, and returning to that orbit after transient perturbation. We found the same attractor in every preparation, and could predict motor output directly from its orbit, yet individual neurons’ participation changed across consecutive locomotion bouts. From these results, we propose that only the low-dimensional dynamics for movement control and not the high-dimensional population activity are consistent within and between nervous systems.

Joint work with Angela Bruno and Bill Frost.