Interactive neuroscience demonstration
A reduced, lamprey-inspired spinal central pattern generator. Watch a non-rhythmic descending command become local alternation, a rostrocaudal phase gradient, and coordinated body movement.
What is biological: lamprey spinal networks can generate fictive locomotor activity without patterned commands from the brain; left and right motor output alternates; activity normally propagates rostrocaudally; and propriospinal coupling helps stabilize intersegmental coordination.
What is reduced: each colored node is a functional population, not one identified neuron. The single-module oscillator is a generic mutual-inhibition-plus-adaptation model. In the multi-module views, each already-established local oscillator is reduced to a phase variable so that the coordination problem remains visible. Eight displayed modules stand in for roughly 100 anatomical segments, so one displayed module represents about 12–13 segments.
Important guardrail: reciprocal inhibition coordinates the two sides in this demonstration, but it is not presented as the sole biological source of lamprey rhythmogenesis. Lamprey hemicords can generate rhythmic bursting.
Animation conventions: moving dashes represent modeled influence, not individual action potentials. In the distributed views the left/right nodes and inhibitory symbols mark the module identity established in Mode 2; those variables are not recomputed once each module is reduced to a phase. Lateral body displacement is drawn as directly proportional to the left–right difference in muscle activation; in a real swimmer, activation leads local curvature by a delay that grows caudally. Water forces, sensory feedback, and detailed muscle mechanics are not simulated.
Coupling asymmetry: ascending coupling is drawn and modeled as the stronger pathway, following evidence that ascending coupling dominates and sets the intersegmental phase lag in lamprey. In this reduced phase model the target lag ψ appears in both coupling terms, so the asymmetry shapes transients and recovery rather than setting the steady-state lag.
Selected sources: Wallén & Williams (1984), fictive locomotion and approximately 1% phase lag per anatomical segment; Buchanan & Grillner (1987), excitatory interneurons in the lamprey locomotor network; Williams (1992), ascending coupling dominance and one wavelength on the body; Cangiano & Grillner (2005), hemicord rhythm generation; Miller & Sigvardt (2000), multisegmental coupling; Matsuoka (1985), mutual inhibition with adaptation as a generic oscillator.