Closed-loop robots driven by short-term synaptic plasticity: Emergent explorative vs. limit-cycle locomotion

TL;DR

This study demonstrates that short-term synaptic plasticity can self-organize diverse and adaptive locomotion patterns in autonomous robots, including chaotic exploration and stable limit cycles, through closed-loop sensorimotor interactions.

Contribution

It provides evidence that transient synaptic plasticity can generate complex, adaptive motor behaviors in robots, highlighting its potential role in biological and artificial locomotion.

Findings

Robots exhibit various locomotion patterns including meandering, circular, and chaotic trajectories.

Locomotion patterns are robust against environmental interactions and obstacle encounters.

Transient synaptic plasticity can produce both stable and chaotic motor behaviors, facilitating environmental exploration.

Abstract

We examine the hypothesis, that short-term synaptic plasticity (STSP) may generate self-organized motor patterns. We simulated sphere-shaped autonomous robots, within the LPZRobots simulation package, containing three weights moving along orthogonal internal rods. The position of a weight is controlled by a single neuron receiving excitatory input from the sensor, measuring its actual position, and inhibitory inputs from the other two neurons. The inhibitory connections are transiently plastic, following physiologically inspired STSP-rules. We find that a wide palette of motion patterns are generated through the interaction of STSP, robot, and environment (closed-loop configuration), including various forward meandering and circular motions, together with chaotic trajectories. The observed locomotion is robust with respect to additional interactions with obstacles. In the chaotic phase the robot is seemingly engaged in actively exploring its environment. We believe that our results constitute a concept of proof that transient synaptic plasticity, as described by STSP, may potentially be important for the generation of motor commands and for the emergence of complex locomotion patterns, adapting seamlessly also to unexpected environmental feedback. We observe spontaneous and collision induced mode switchings, finding in addition, that locomotion may follow transiently limit cycles which are otherwise unstable. Regular locomotion corresponds to stable limit cycles in the sensorimotor loop, which may be characterized in turn by arbitrary angles of propagation. This degeneracy is, in our analysis, one of the drivings for the chaotic wandering observed for selected parameter settings, which is induced by the smooth diffusion of the angle of propagation.